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Sedentary Behaviour as an Emerging Risk Factor for Cardiometabolic Diseases in Children and Youth

  • Travis J. Saunders
    Correspondence
    Address for correspondence: Travis J. Saunders, MSc, PhD, Healthy Active Living and Obesity Research Group, Children's Hospital of Eastern Ontario Research Institute, Room R242, 401 Smyth Road, Ottawa, Ontario K1H 8L1, Canada.
    Affiliations
    Healthy Active Living and Obesity Research Group, Children's Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada

    School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
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  • Jean-Philippe Chaput
    Affiliations
    Healthy Active Living and Obesity Research Group, Children's Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada

    School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
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  • Mark S. Tremblay
    Affiliations
    Healthy Active Living and Obesity Research Group, Children's Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada

    School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
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      Abstract

      Sedentary behaviour (e.g. TV viewing, seated video game playing, prolonged sitting) has recently emerged as a distinct risk factor for cardiometabolic diseases in children and youth. This narrative review provides an overview of recent evidence in this area and highlights research gaps. Current evidence suggests that North American children and youth spend between 40% and 60% of their waking hours engaging in sedentary pursuits. Although data are lacking concerning temporal trends of objectively measured sedentary time, self-reported sedentary behaviours have increased over the past half century, with a rapid increase since the late 1990s. Excessive sedentary behaviour has been found to have independent and deleterious associations with markers of adiposity and cardiometabolic disease risk. These associations are especially consistent for screen-based sedentary behaviours (TV viewing, computer games, etc), with more conflicting findings observed for overall sedentary time. The above associations are possibly mediated by the influence of screen-based sedentary behaviours on energy intake. Although excessive sitting has been reported to have adverse acute and chronic metabolic impacts in adults, research on children is lacking. Research is particularly needed to investigate the impact of characteristics of sedentary behaviour (i.e. type/context, sedentary bout length, breaks in sedentary time, etc), as well as interventions that examine the health and behavioural impacts of sitting per se.

      Résumé

      Le comportement sédentaire (p. ex. l'écoute de la télévision, la pratique des jeux vidéo en position assise, la position assise prolongée) s'est récemment imposé comme un facteur de risque distinct des maladies cardiométaboliques chez les enfants et les jeunes. Cette revue narrative offre un aperçu des données scientifiques récentes dans ce domaine et souligne les lacunes en matière de recherche. Les données scientifiques actuelles montrent que les enfants et les jeunes de l'Amérique du Nord passent entre 40 % et 60 % de leur journée à faire des activités sédentaires. Bien qu'il manque de données sur les tendances temporelles du temps consacré à des activités sédentaires mesurées de manière objective, les comportements sédentaires qui sont rapportés ont augmenté au cours de la seconde moitié du siècle dernier, et ce, plus rapidement depuis la fin des années 1990. Le comportement sédentaire excessif a montré des liens indépendants et délétères avec les marqueurs de l'adiposité et du risque de maladie cardiométabolique. Ces liens sont particulièrement cohérents pour ce qui est des comportements sédentaires liés au temps passé devant un écran (écoute de la télévision, jeux sur ordinateur, etc.), et des résultats plus contradictoires ont été observés pour l'ensemble du temps consacré à des activités sédentaires. Les liens susmentionnés sont possiblement influencés par les comportements sédentaires liés au temps passé devant un écran. Bien que la position assise excessive soit rapportée comme ayant des conséquences métaboliques indésirables à court et à long terme chez les adultes, il manque de recherches en ce qui a trait aux enfants. La recherche est nécessaire en particulier pour étudier les conséquences des caractéristiques du comportement sédentaire (c.-à-d. type/contexte, durée des périodes de sédentarité, pauses durant le temps consacré à des activités sédentaires, etc.) ainsi que les interventions qui examinent les conséquences sur la santé et le comportement de la position assise en soi.

      Keywords

      Mots clés

      Introduction

      It is well established that high levels of physical activity are associated with reduced health risk in children and youth (
      • Janssen I.
      • LeBlanc A.G.
      Systematic review of the health benefits of physical activity and fitness in school-aged children and youth.
      ,
      • Andersen L.B.
      • Harro M.
      • Sardinha L.B.
      • et al.
      Physical activity and clustered cardiovascular risk in children: a cross-sectional study (The European Youth Heart Study).
      ,
      • Schmitz K.H.
      • Jacobs D.R.
      • Hong C.P.
      • et al.
      Association of physical activity with insulin sensitivity in children.
      ). Physical activity exhibits a dose-response relationship with health indicators in the pediatric population, and even modest amounts of physical activity can result in improved health for those at greatest risk (
      • Janssen I.
      • LeBlanc A.G.
      Systematic review of the health benefits of physical activity and fitness in school-aged children and youth.
      ). However, in addition to the consistent association between physical activity and health in the pediatric population, accumulating evidence suggests that the amount of time children and youth spend engaging in sedentary behaviours (i.e. activities that involve sitting or reclining while expending ≤1.5 metabolic equivalents [
      • Sedentary Behaviour Research Network
      Standardized use of the terms “sedentary” and “sedentary behaviours” [letter to the editor].
      ]) may be associated with increased cardiometabolic disease risk independent of other factors, such as physical activity and abdominal obesity (
      • Sardinha L.B.
      • Andersen L.B.
      • Anderssen S.A.
      • et al.
      Objectively measured time spent sedentary is associated with insulin resistance independent of overall and central body fat in 9- to 10-year-old Portuguese children.
      ,
      • Danielsen Y.
      • Júlíusson P.
      • Nordhus I.
      • et al.
      The relationship between life-style and cardio-metabolic risk indicators in children: the importance of screen time.
      ,
      • Ekelund U.
      • Brage S.
      • Froberg K.
      • et al.
      TV viewing and physical activity are independently associated with metabolic risk in children: The European Youth Heart Study.
      ,
      • Mark A.E.
      • Janssen I.
      Relationship between screen time and metabolic syndrome in adolescents.
      ,
      • Goldfield G.S.
      • Saunders T.J.
      • Kenny G.P.
      • et al.
      Screen viewing and diabetes risk factors in overweight and obese adolescents.
      ,
      • Goldfield G.S.
      • Kenny G.P.
      • Hadjiyannakis S.
      • et al.
      Video game playing is independently associated with blood pressure and lipids in overweight and obese adolescents.
      ,
      • Tremblay M.S.
      • LeBlanc A.G.
      • Janssen I.
      • et al.
      Canadian sedentary behaviour guidelines for children and youth.
      ,
      • Cliff D.P.
      • Okely A.D.
      • Burrows T.L.
      • et al.
      Objectively measured sedentary behavior, physical activity, and plasma lipids in overweight and obese children.
      ). In response to this new research, Canada has recently created pediatric sedentary behaviour guidelines, which are separate from (but complementary to) physical activity guidelines for this age group (
      • Tremblay M.S.
      • LeBlanc A.G.
      • Janssen I.
      • et al.
      Canadian sedentary behaviour guidelines for children and youth.
      ). These guidelines recommend that school-aged children and youth accumulate no more than 2 hours of recreational screen time each day and that they also limit periods of prolonged sitting and motorized transport (
      • Tremblay M.S.
      • LeBlanc A.G.
      • Janssen I.
      • et al.
      Canadian sedentary behaviour guidelines for children and youth.
      ). Although a number of recent narrative reviews have examined the health impacts of sedentary behaviour in adults (
      • Hamilton M.T.
      • Hamilton D.G.
      • Zderic T.W.
      Role of low energy expenditure and sitting in obesity, metabolic syndrome, type 2 diabetes, and cardiovascular disease.
      ,
      • Hamilton M.T.
      • Hamilton D.G.
      • Zderic T.W.
      Exercise physiology versus inactivity physiology: an essential concept for understanding lipoprotein lipase regulation.
      ,
      • Tremblay M.S.
      • Colley R.C.
      • Saunders T.J.
      • et al.
      Physiological and health implications of a sedentary lifestyle.
      ,
      • Hamilton M.T.
      • Healy G.N.
      • Dunstan D.W.
      • et al.
      Too little exercise and too much sitting: inactivity physiology and the need for new recommendations on sedentary behavior.
      ,
      • Bergouignan A.
      • Rudwill F.
      • Simon C.
      • et al.
      Physical inactivity as the culprit of metabolic inflexibility: evidence from bed-rest studies.
      ), there is a lack of such a review in the pediatric population. Thus, this article aims to provide a comprehensive overview of the available evidence concerning sedentary behaviour and markers of cardiometabolic disease risk in school-aged children and youth.

      What is sedentary behaviour?

      The meaning of the word sedentary has evolved rapidly in recent years (
      • Pate R.R.
      • O'Neill J.R.
      • Lobelo F.
      The evolving definition of “sedentary.”.
      ). Although the Latin root of the word sedentary literally means to sit (
      • Tremblay M.S.
      • Colley R.C.
      • Saunders T.J.
      • et al.
      Physiological and health implications of a sedentary lifestyle.
      ), the term has historically been used by health researchers to refer to an individual who is not sufficiently physically active (
      • Sedentary Behaviour Research Network
      Standardized use of the terms “sedentary” and “sedentary behaviours” [letter to the editor].
      ). Similarly, the phrase sedentary lifestyle has typically been used to refer to a lifestyle that includes little or no physical activity (
      • Manson J.E.
      • Skerrett P.J.
      • Greenland P.
      The escalating pandemics of obesity and sedentary lifestyle: A call to action for clinicians.
      ). It has, therefore, been relatively common for researchers to refer to individuals as sedentary because of their lack of physical activity, rather than the amount of time they spend sitting. However, recent evidence suggests that sitting too much and exercising too little are separate and distinct risk factors for chronic diseases, including cancer, cardiovascular disease and diabetes (
      • Tremblay M.S.
      • Colley R.C.
      • Saunders T.J.
      • et al.
      Physiological and health implications of a sedentary lifestyle.
      ,
      • Hamilton M.T.
      • Healy G.N.
      • Dunstan D.W.
      • et al.
      Too little exercise and too much sitting: inactivity physiology and the need for new recommendations on sedentary behavior.
      ,
      • Wilmot E.G.
      • Edwardson C.L.
      • Achana F.A.
      • et al.
      Sedentary time in adults and the association with diabetes, cardiovascular disease and death: systematic review and meta-analysis.
      ,
      • Lynch B.M.
      Sedentary behavior and cancer: a systematic review of the literature and proposed biological mechanisms.
      ). Further, individuals can easily meet physical activity guidelines while spending the vast majority of their days engaging in seated activities or vice versa (Figure 1). As a result, it has been proposed that the term sedentary should be used to refer only to activities that are defined by both seated and reclining postures and energy expenditures at or near resting levels (
      • Sedentary Behaviour Research Network
      Standardized use of the terms “sedentary” and “sedentary behaviours” [letter to the editor].
      ). Therefore, in this review the term sedentary is used to refer specifically to waking behaviours characterized by energy expenditure ≤1.5 metabolic equivalents while in a sitting or reclining posture (
      • Sedentary Behaviour Research Network
      Standardized use of the terms “sedentary” and “sedentary behaviours” [letter to the editor].
      ). In contrast, the term inactive is used to refer to an individual who is not sufficiently physically active (e.g. not meeting physical activity guidelines).
      Figure thumbnail gr1
      Figure 1Sedentary behaviour and physical activity as distinct constructs.

      How is pediatric sedentary behaviour measured?

      As with physical activity, sedentary behaviour can be assessed using a variety of self- and proxy-report questionnaires or by direct measurement tools (
      • Tremblay M.S.
      • Colley R.C.
      • Saunders T.J.
      • et al.
      Physiological and health implications of a sedentary lifestyle.
      ,
      • Lubans D.R.
      • Hesketh K.
      • Cliff D.P.
      • et al.
      A systematic review of the validity and reliability of sedentary behaviour measures used with children and adolescents.
      ,
      • Colley R.C.
      • Wong S.L.
      • Garriguet D.
      • et al.
      Physical activity, sedentary behaviour and sleep in Canadian children: parent-report versus direct measures and relative associations with health risk.
      ). Self- and proxy-report tools typically take 1 of 2 approaches: 1) asking children or their parents to estimate the amount of time they spend engaging in common sedentary behaviours (e.g. watching television, using a computer, playing passive video games, driving in a car, etc), which may be reflective of total sedentary time or 2) asking them to estimate the amount of total time, on a daily basis, they spend sitting. These tools are attractive because they are inexpensive and result in data that are relatively simple to analyze while providing information related to specific modalities or contexts of sedentary behaviours (e.g. television viewing vs. reading). A recent systematic review suggests that self- and proxy-report tools generally display acceptable reliability and validity in assessing sedentary behaviour (
      • Lubans D.R.
      • Hesketh K.
      • Cliff D.P.
      • et al.
      A systematic review of the validity and reliability of sedentary behaviour measures used with children and adolescents.
      ). However, these measures have a number of limitations. First and foremost, they are known to be limited by high levels of error and recall bias (
      • Colley R.C.
      • Wong S.L.
      • Garriguet D.
      • et al.
      Physical activity, sedentary behaviour and sleep in Canadian children: parent-report versus direct measures and relative associations with health risk.
      ,
      • Adamo K.B.
      • Prince S.A.
      • Tricco A.C.
      • et al.
      A comparison of indirect versus direct measures for assessing physical activity in the pediatric population: a systematic review.
      ,
      • Prince S.A.
      • Adamo K.B.
      • Hamel M.E.
      • et al.
      A comparison of direct versus self-report measures for assessing physical activity in adults: a systematic review.
      ,
      • Saunders T.J.
      • Prince S.A.
      • Tremblay M.S.
      Clustering of children's activity behaviour: the use of self-report versus direct measures.
      ). Further, no single sedentary activity is representative of an individual's total sedentary behaviour profile (
      • Colley R.C.
      • Wong S.L.
      • Garriguet D.
      • et al.
      Physical activity, sedentary behaviour and sleep in Canadian children: parent-report versus direct measures and relative associations with health risk.
      ,
      • Biddle S.J.
      • Gorely T.
      • Marshall S.J.
      Is television viewing a suitable marker of sedentary behavior in young people?.
      ,
      • Sugiyama T.
      • Healy G.N.
      • Dunstan D.W.
      • et al.
      Is television viewing time a marker of a broader pattern of sedentary behavior?.
      ), which can pose an issue when data collection focuses on a limited number of sedentary behaviour modalities.
      In contrast to self-report tools, accelerometers and inclinometers allow for the direct measurement of sedentary behaviour in childhood (
      • Tremblay M.S.
      • Colley R.C.
      • Saunders T.J.
      • et al.
      Physiological and health implications of a sedentary lifestyle.
      ,
      • Lubans D.R.
      • Hesketh K.
      • Cliff D.P.
      • et al.
      A systematic review of the validity and reliability of sedentary behaviour measures used with children and adolescents.
      ,
      • Colley R.C.
      • Wong S.L.
      • Garriguet D.
      • et al.
      Physical activity, sedentary behaviour and sleep in Canadian children: parent-report versus direct measures and relative associations with health risk.
      ). Accelerometers assess the number of movement “counts” in a given time period, and their use has increased rapidly in recent years (
      • Cain K.L.
      • Sallis J.F.
      • Conway T.L.
      • et al.
      Using accelerometers in youth physical activity studies: a review of methods.
      ). A variety of thresholds have been proposed to distinguish between sedentary behaviour and light-intensity physical activity, with a threshold of 100 counts per minute (CPM) being shown to have high sensitivity and specificity for the measurement of sedentary behaviour in pediatric populations using both ActiGraph (ActiGraph, Pensacola, FL, US) and Actical (Philips Respironics, Andover, MA, US) accelerometers (
      • Lubans D.R.
      • Hesketh K.
      • Cliff D.P.
      • et al.
      A systematic review of the validity and reliability of sedentary behaviour measures used with children and adolescents.
      ,
      • Treuth M.S.
      • Schmitz K.H.
      • Catellier D.
      • et al.
      Defining accelerometer thresholds for activity intensities in adolescent girls.
      ,
      • Evenson K.R.
      • Catellier D.J.
      • Gill K.
      • et al.
      Calibration of two objective measures of physical activity for children.
      ,
      • Ridgers N.D.
      • Salmon J.
      • Ridley K.
      • et al.
      Agreement between activPAL and ActiGraph for assessing children's sedentary time.
      ,
      • Trost S.G.
      • Pate R.R.
      • Sallis J.F.
      • et al.
      Age and gender differences in objectively measured physical activity in youth.
      ,
      • Trost S.G.
      • Loprinzi P.D.
      • Moore R.
      • et al.
      Comparison of accelerometer cut points for predicting activity intensity in youth.
      ,
      • Puyau M.R.
      • Adolph A.L.
      • Vohra F.A.
      • et al.
      Prediction of activity energy expenditure using accelerometers in children.
      ,
      • Wong S.L.
      • Colley R.
      • Connor-Gorber S.
      • et al.
      Actical accelerometer sedentary activity thresholds for adults.
      ). Accelerometers can also be used to assess the frequency of breaks in sedentary time and the duration of sedentary bouts, neither of which can be determined easily via self-report tools (
      • Colley R.C.
      • Garriguet D.
      • Janssen I.
      • et al.
      The association between accelerometer-measured patterns of sedentary time and health risk in children and youth: a cross-sectional study.
      ,
      • Healy G.N.
      • Dunstan D.W.
      • Salmon J.
      • et al.
      Breaks in sedentary time: beneficial associations with metabolic risk.
      ,
      • Healy G.N.
      • Matthews C.E.
      • Dunstan D.W.
      • et al.
      Sedentary time and cardio-metabolic biomarkers in US adults: NHANES 2003-06.
      ). However, a key limitation of accelerometers is their inability to distinguish between sitting and stationary standing (
      • Dowd K.P.
      • Harrington D.M.
      • Donnelly A.E.
      Criterion and concurrent validity of the Activpaltm professional physical activity monitor in adolescent females.
      ) and the lack of information regarding the modality of sedentary behaviour (e.g. TV viewing vs. reading). Inclinometers such as the activPAL (PAL Technologies, Glasgow, UK) have been reported to be more accurate than accelerometers in differentiating between sitting and standing (
      • Dowd K.P.
      • Harrington D.M.
      • Donnelly A.E.
      Criterion and concurrent validity of the Activpaltm professional physical activity monitor in adolescent females.
      ,
      • Aminian S.
      • Hinckson E.A.
      Examining the validity of the ActivPAL monitor in measuring posture and ambulatory movement in children.
      ), with Aminian and Hinckson reporting that the activPAL was able to distinguish perfectly between the 2 postures in healthy elementary school children (
      • Aminian S.
      • Hinckson E.A.
      Examining the validity of the ActivPAL monitor in measuring posture and ambulatory movement in children.
      ). As with accelerometers, however, inclinometers are unable to provide information on the modality of sedentary behaviour and have been used far less frequently. As a result of the limitations of both self-report and direct-measurement tools, researchers have, therefore, advocated for the concurrent use of both strategies whenever possible (
      • Lubans D.R.
      • Hesketh K.
      • Cliff D.P.
      • et al.
      A systematic review of the validity and reliability of sedentary behaviour measures used with children and adolescents.
      ,
      • Colley R.C.
      • Wong S.L.
      • Garriguet D.
      • et al.
      Physical activity, sedentary behaviour and sleep in Canadian children: parent-report versus direct measures and relative associations with health risk.
      ).

      Prevalence of sedentary behaviour in the pediatric population

      Available evidence suggests that children and youth in developed nations currently spend 40% to 60% of their waking hours engaging in sedentary pursuits. Colley et al used accelerometers to assess total sedentary time in a representative sample of 1608 Canadians between the ages of 6 and 19 years (
      • Colley R.C.
      • Garriguet D.
      • Janssen I.
      • et al.
      The association between accelerometer-measured patterns of sedentary time and health risk in children and youth: a cross-sectional study.
      ,
      • Colley R.
      • Garriguet D.
      • Janssen I.
      • et al.
      Physical activity of Canadian children and youth: accelerometer results from the 2007 to 2009 Canadian Health Measures Survey.
      ). They estimated that girls and boys, respectively, accumulate 7.4 and 8.5 hours of daily sedentary time, roughly half of which is accumulated during school hours (
      • Colley R.C.
      • Garriguet D.
      • Janssen I.
      • et al.
      The association between accelerometer-measured patterns of sedentary time and health risk in children and youth: a cross-sectional study.
      ,
      • Colley R.
      • Garriguet D.
      • Janssen I.
      • et al.
      Physical activity of Canadian children and youth: accelerometer results from the 2007 to 2009 Canadian Health Measures Survey.
      ). Sedentary time also tends to increase with age; children under 11 years averaged approximately 1.3 hours less daily sedentary time than those aged 11 to 14 years of age and roughly 2 hours less than those 15 to 19 years of age (
      • Colley R.
      • Garriguet D.
      • Janssen I.
      • et al.
      Physical activity of Canadian children and youth: accelerometer results from the 2007 to 2009 Canadian Health Measures Survey.
      ). Similar levels and trends for accelerometer-derived sedentary behaviour have been reported in cross-sectional examinations of American (
      • Matthews C.E.
      • Chen K.Y.
      • Freedson P.S.
      • et al.
      Amount of time spent in sedentary behaviors in the United States, 2003–2004.
      ) and European (
      • Pate R.R.
      • Mitchell J.A.
      • Byun W.
      • et al.
      Sedentary behaviour in youth.
      ) children and youth.
      The above-mentioned findings are also supported by longitudinal studies, which suggest that both screen time and total sedentary time increase with age (
      • Trang N.H.
      • Hong T.K.
      • van der Ploeg H.P.
      • et al.
      Longitudinal sedentary behavior changes in adolescents in Ho Chi Minh City.
      ,
      • Brodersen N.H.
      • Steptoe A.
      • Boniface D.R.
      • et al.
      Trends in physical activity and sedentary behaviour in adolescence: ethnic and socioeconomic differences.
      ). For example, a longitudinal study of 759 Vietnamese students observed that boys and girls increased their daily sedentary time by more than 1 hour between the ages of 13 and 16 years (
      • Trang N.H.
      • Hong T.K.
      • van der Ploeg H.P.
      • et al.
      Longitudinal sedentary behavior changes in adolescents in Ho Chi Minh City.
      ). Similarly, Brodersen et al found that self-reported screen time increased by more than 2.5 hours per week during a 5-year period in a study of 5863 British adolescents (
      • Brodersen N.H.
      • Steptoe A.
      • Boniface D.R.
      • et al.
      Trends in physical activity and sedentary behaviour in adolescence: ethnic and socioeconomic differences.
      ). It is worth noting that the frequency of breaks in sedentary time also appears to decrease with age; a longitudinal study of roughly 500 children found a decrease of approximately 2 breaks per hour per year from age 5 to age 15 (
      • Kwon S.
      • Burns T.L.
      • Levy S.M.
      • et al.
      Breaks in sedentary time during childhood and adolescence: Iowa bone development study.
      ). These findings suggest that children become more sedentary with age and also accumulate their sedentary time in increasingly prolonged bouts.

      Temporal trends in sedentary behaviour among children and youth

      Given the relatively recent introduction of accelerometry in population-based research, it is difficult to assess temporal trends in objectively measured sedentary time. However, self-reported media use (including TV, radio, audio, reading, etc) appears to have increased since the 1960s, with rapid increases observed in the past decade. Schramm et al (
      • Schramm W.
      • Lyle J.
      • Parker E.
      Television in the lives of our children.
      ) reported that American children in grades 6 and 12 averaged roughly 37 hours per week of total media exposure in 1961. In contrast, recent evidence from the Kaiser Family Foundation reported that American children between the ages of 8 and 18 years averaged 53 hours per week of total media exposure in 1999, and 75 hours in 2009 (
      • Rideout V.
      • Foehr U.
      • Roberts D.
      Generation M2: Media in the lives of 8- to 18-year-olds.
      ) (Figure 2). After adjusting for multitasking (e.g. engaging with 2 forms of media simultaneously), the average American youth currently spends 54 hours engaging with media each week (
      • Rideout V.
      • Foehr U.
      • Roberts D.
      Generation M2: Media in the lives of 8- to 18-year-olds.
      ). The same report estimated that total media use increased by 1.5 hours per day among Caucasian American children between 1999 and 2009 and by more than 3 hours per day among African American and Hispanic children over the same period (
      • Rideout V.
      • Foehr U.
      • Roberts D.
      Generation M2: Media in the lives of 8- to 18-year-olds.
      ). A nationally representative study of 52 000 children and youth produced a similar estimate of total daily screen time among contemporary Canadian students (
      • Leatherdale S.T.
      • Ahmed R.
      Screen-based sedentary behaviours among a nationally representative sample of youth: are Canadian kids couch potatoes?.
      ), and temporal increases in self-reported screen time have also been reported in Czech girls (but not boys) (
      • Sigmundova D.
      • El Ansari W.
      • Sigmund E.
      • et al.
      Secular trends: a ten-year comparison of the amount and type of physical activity and inactivity of random samples of adolescents in the Czech Republic.
      ) and in Chinese children and youth (
      • Mak K.-K.
      • Day J.R.
      Secular trends of sports participation, sedentary activity and physical self-perceptions in Hong Kong adolescents, 1995-2000.
      ,
      • Cui Z.
      • Hardy L.L.
      • Dibley M.J.
      • et al.
      Temporal trends and recent correlates in sedentary behaviours in Chinese children.
      ) during the late 1990s and early 2000s, although reductions in total screen time have been reported in Norwegian children (
      • Øverby N.C.
      • Klepp K.-I.
      • Bere E.
      Changes in screen time activity in Norwegian children from 2001 to 2008: two cross-sectional studies.
      ) and Czech boys (
      • Sigmundova D.
      • El Ansari W.
      • Sigmund E.
      • et al.
      Secular trends: a ten-year comparison of the amount and type of physical activity and inactivity of random samples of adolescents in the Czech Republic.
      ). Consequently, it is not surprising that the majority of children in developed nations currently exceed the recommendations for pediatric screen time (
      • Tremblay M.S.
      • LeBlanc A.G.
      • Janssen I.
      • et al.
      Canadian sedentary behaviour guidelines for children and youth.
      ,

      Australian Government Department of Health and Ageing. Sedentary behaviour and screen-time. http://www.health.gov.au/internet/publications/publishing.nsf/Content/gug-director-toc∼gug-sedentary. Accessed May 14, 2013.

      ).
      Figure thumbnail gr2
      Figure 2Self-reported media exposure of American youth over time.
      Data from Schramm et al (
      • Schramm W.
      • Lyle J.
      • Parker E.
      Television in the lives of our children.
      ) and Rideout et al (
      • Rideout V.
      • Foehr U.
      • Roberts D.
      Generation M2: Media in the lives of 8- to 18-year-olds.
      ). Data have not been adjusted for multitasking (e.g. engaging with multiple media simultaneously).
      Along with the reported increases in total screen time, there has also been a shift away from TV viewing and toward increased computer and video game use in recent decades (
      • Rideout V.
      • Foehr U.
      • Roberts D.
      Generation M2: Media in the lives of 8- to 18-year-olds.
      ,
      • Sigmundova D.
      • El Ansari W.
      • Sigmund E.
      • et al.
      Secular trends: a ten-year comparison of the amount and type of physical activity and inactivity of random samples of adolescents in the Czech Republic.
      ,
      • Biddle S.J.
      • Gorely T.
      • Marshall S.J.
      • et al.
      Physical activity and sedentary behaviours in youth: issues and controversies.
      ,

      Silva KS, da Silva Lopes A, Dumith SC, et al. Changes in television viewing and computers/videogames use among high school students in Southern Brazil between 2001 and 2011. Int J Public Health (in press).

      ). In a study of Czech children, between 1998 and 2008, the percent of sedentary time accounted for by TV viewing decreased from 17% to 12% among girls and from 24% to 15% among boys (
      • Sigmundova D.
      • El Ansari W.
      • Sigmund E.
      • et al.
      Secular trends: a ten-year comparison of the amount and type of physical activity and inactivity of random samples of adolescents in the Czech Republic.
      ). During the same period, the proportion of sedentary time accounted for by computer use more than doubled in both sexes (
      • Sigmundova D.
      • El Ansari W.
      • Sigmund E.
      • et al.
      Secular trends: a ten-year comparison of the amount and type of physical activity and inactivity of random samples of adolescents in the Czech Republic.
      ). Finally, evidence suggests that sedentary modes of transportation (e.g. driving) have also increased dramatically since the 1960s throughout the Western world (
      • Buliung R.N.
      • Mitra R.
      • Faulkner G.
      Active school transportation in the Greater Toronto Area, Canada: an exploration of trends in space and time (1986-2006).
      ,
      • McDonald N.C.
      Active transportation to school: trends among U.S. schoolchildren, 1969-2001.
      ,
      • Van der Ploeg H.P.
      • Merom D.
      • Corpuz G.
      • et al.
      Trends in Australian children traveling to school 1971-2003: burning petrol or carbohydrates?.
      ). Taken together, the above evidence suggests that the volume of total daily sedentary time has likely increased in the past 50 years, with computer and video-game use playing a larger role in recent years.

      Sedentary time and markers of adiposity in children and youth

      A recent systematic review by Tremblay et al (
      • Tremblay M.
      • LeBlanc A.G.
      • Kho M.
      • et al.
      Systematic review of sedentary behaviour and health indicators in school-aged children and youth.
      ) examined the relationship between sedentary behaviour (typically assessed via self- or proxy-reported screen time) and adiposity in 170 separate studies of school-aged children. Among 119 cross-sectional studies, 94 observed positive associations between sedentary behaviour and markers of adiposity. Further, the risk of being identified as obese increased in a dose-response manner with sedentary time. For example, in a sample of 461 Mexican children and youth, Hernández and colleagues observed that the odds of being classified as obese increased by 12% for every hour of self-reported television viewing (
      • Hernández B.
      • Gortmaker S.L.
      • Colditz G.A.
      • et al.
      Association of obesity with physical activity, television programs and other forms of video viewing among children in Mexico city.
      ). These cross-sectional findings are also supported by longitudinal evidence (
      • Tremblay M.
      • LeBlanc A.G.
      • Kho M.
      • et al.
      Systematic review of sedentary behaviour and health indicators in school-aged children and youth.
      ,
      • Kaur H.
      • Choi W.S.
      • Mayo M.S.
      • et al.
      Duration of television watching is associated with increased body mass index.
      ,
      • Mitchell J.A.
      • Pate R.R.
      • Beets M.W.
      • et al.
      Time spent in sedentary behavior and changes in childhood BMI: a longitudinal study from ages 9 to 15 years.
      ). Mitchell et al (
      • Mitchell J.A.
      • Pate R.R.
      • Beets M.W.
      • et al.
      Time spent in sedentary behavior and changes in childhood BMI: a longitudinal study from ages 9 to 15 years.
      ) showed that objectively measured sedentary time was independently associated with increased weight gain between 9 and 15 years of age among children in the 50th, 75th and 90th body weight percentiles, independent of other covariates, including physical activity, sleep and diet.
      Finally, evidence from randomized controlled trials demonstrates that reductions in sedentary time may result in reductions in adiposity (
      • Tremblay M.
      • LeBlanc A.G.
      • Kho M.
      • et al.
      Systematic review of sedentary behaviour and health indicators in school-aged children and youth.
      ,
      • Robinson T.N.
      Reducing children's television viewing to prevent obesity: a randomized controlled trial.
      ,
      • Epstein L.H.
      • Roemmich J.N.
      • Robinson J.L.
      • et al.
      A randomized trial of the effects of reducing television viewing and computer use on body mass index in young children.
      ). For example, Robinson reported that elementary school children who were randomized to receive an intervention aimed at reducing screen time experienced a 0.45 kg/m2 reduction in body mass index (BMI) and a 2.30 cm reduction in waist circumference when compared to control students over a 6-month period (
      • Robinson T.N.
      Reducing children's television viewing to prevent obesity: a randomized controlled trial.
      ). These findings are supported by a recent systematic review and meta-analysis, which concluded that interventions that reduce sedentary behaviour in children result in a mean decrease in BMI of 0.89 kg/m2 (
      • Tremblay M.
      • LeBlanc A.G.
      • Kho M.
      • et al.
      Systematic review of sedentary behaviour and health indicators in school-aged children and youth.
      ). These results suggest that sedentary behaviour (especially screen time) has an independent and causal influence on the risk for excess weight gain and obesity in the pediatric age group (
      • Tremblay M.
      • LeBlanc A.G.
      • Kho M.
      • et al.
      Systematic review of sedentary behaviour and health indicators in school-aged children and youth.
      ,

      Saunders TJ. Potential contributors to the Canadian pediatric obesity epidemic. ISRN Pediatr vol 2011, Article ID 917684, 2011. http://dx.doi.org/10.5402/2011/917684.

      ).

      Sedentary time and markers of cardiometabolic disease risk in children and youth

      Although it has been the focus of less research than adiposity, emerging evidence suggests that sedentary behaviour is also independently associated with other markers of cardiometabolic disease risk in children and youth (
      • Sardinha L.B.
      • Andersen L.B.
      • Anderssen S.A.
      • et al.
      Objectively measured time spent sedentary is associated with insulin resistance independent of overall and central body fat in 9- to 10-year-old Portuguese children.
      ,
      • Mark A.E.
      • Janssen I.
      Relationship between screen time and metabolic syndrome in adolescents.
      ,
      • Goldfield G.S.
      • Saunders T.J.
      • Kenny G.P.
      • et al.
      Screen viewing and diabetes risk factors in overweight and obese adolescents.
      ,
      • Goldfield G.S.
      • Kenny G.P.
      • Hadjiyannakis S.
      • et al.
      Video game playing is independently associated with blood pressure and lipids in overweight and obese adolescents.
      ,
      • Cliff D.P.
      • Okely A.D.
      • Burrows T.L.
      • et al.
      Objectively measured sedentary behavior, physical activity, and plasma lipids in overweight and obese children.
      ,
      • Tremblay M.
      • LeBlanc A.G.
      • Kho M.
      • et al.
      Systematic review of sedentary behaviour and health indicators in school-aged children and youth.
      ,
      • Chaput J.P.
      • Saunders T.J.
      • Mathieu M.E.
      • et al.
      Combined associations between moderate to vigorous physical activity and sedentary behavior with cardiometabolic risk factors in children.
      ,
      • Henderson M.
      • Gray-Donald K.
      • Mathieu M.E.
      • et al.
      How are physical activity, fitness, and sedentary behavior associated with insulin sensitivity in children?.
      ,
      • Carson V.
      • Janssen I.
      Volume, patterns, and types of sedentary behavior and cardio-metabolic health in children and adolescents: a cross-sectional study.
      ,
      • Kriska A.
      • Delahanty L.
      • Edelstein S.
      • et al.
      Sedentary behavior and physical activity in youth with recent onset of type 2 diabetes.
      ). Goldfield et al have recently reported that television viewing and video game playing are associated with risk factors for diabetes and cardiovascular disease, respectively, independent of physical activity in overweight and obese adolescents (
      • Goldfield G.S.
      • Saunders T.J.
      • Kenny G.P.
      • et al.
      Screen viewing and diabetes risk factors in overweight and obese adolescents.
      ,
      • Goldfield G.S.
      • Kenny G.P.
      • Hadjiyannakis S.
      • et al.
      Video game playing is independently associated with blood pressure and lipids in overweight and obese adolescents.
      ). Similarly, Kriska et al (
      • Kriska A.
      • Delahanty L.
      • Edelstein S.
      • et al.
      Sedentary behavior and physical activity in youth with recent onset of type 2 diabetes.
      ) observed that in comparison to obese youth without diabetes, those recently diagnosed with diabetes accumulated roughly 1 additional hour of objectively measured sedentary time each day. These results are also supported by a recent report by Wennberg et al (
      • Wennberg P.
      • Gustafsson P.E.
      • Dunstan D.W.
      • et al.
      Television viewing and low leisure-time physical activity in adolescence independently predict the metabolic syndrome in mid-adulthood.
      ), who found that self-reported TV viewing at age 16 is prospectively associated with the risk for metabolic syndrome at 43 years of age. Participants who reported watching “several TV shows a day” at baseline had twice the odds of having metabolic syndrome at follow up, independent of physical activity, socioeconomic status and family history of diabetes. Associations were also seen for individual metabolic syndrome components, including central obesity, lipids and blood pressure (
      • Wennberg P.
      • Gustafsson P.E.
      • Dunstan D.W.
      • et al.
      Television viewing and low leisure-time physical activity in adolescence independently predict the metabolic syndrome in mid-adulthood.
      ). As with adiposity, these findings suggest that sedentary behaviour (typically measured as self-reported screen time) is independently associated with increased cardiometabolic disease risk in the pediatric population.

      The role of sedentary behaviour modality: screen based vs. non-screen-based sedentary time

      In the 5-year span between 2005 and 2010, the number of investigations assessing sedentary behaviour using objective measures doubled (
      • Cain K.L.
      • Sallis J.F.
      • Conway T.L.
      • et al.
      Using accelerometers in youth physical activity studies: a review of methods.
      ). As the volume of studies using both objective measures of sedentary behaviour (which assess total sedentary time) and self-reported sedentary behaviour (which typically focuses on specific sedentary behaviours such as screen time) has increased, a surprising trend has become apparent in the literature. While self-reported screen time is consistently associated with increased adiposity and risk for cardiometabolic disease in children and youth, independent of physical activity levels (
      • Ekelund U.
      • Brage S.
      • Froberg K.
      • et al.
      TV viewing and physical activity are independently associated with metabolic risk in children: The European Youth Heart Study.
      ,
      • Mark A.E.
      • Janssen I.
      Relationship between screen time and metabolic syndrome in adolescents.
      ,
      • Goldfield G.S.
      • Saunders T.J.
      • Kenny G.P.
      • et al.
      Screen viewing and diabetes risk factors in overweight and obese adolescents.
      ,
      • Goldfield G.S.
      • Kenny G.P.
      • Hadjiyannakis S.
      • et al.
      Video game playing is independently associated with blood pressure and lipids in overweight and obese adolescents.
      ,
      • Tremblay M.
      • LeBlanc A.G.
      • Kho M.
      • et al.
      Systematic review of sedentary behaviour and health indicators in school-aged children and youth.
      ,
      • Chaput J.P.
      • Saunders T.J.
      • Mathieu M.E.
      • et al.
      Combined associations between moderate to vigorous physical activity and sedentary behavior with cardiometabolic risk factors in children.
      ,
      • Carson V.
      • Janssen I.
      Volume, patterns, and types of sedentary behavior and cardio-metabolic health in children and adolescents: a cross-sectional study.
      ,
      • Hsu Y.W.
      • Belcher B.R.
      • Ventura E.E.
      • et al.
      Physical activity, sedentary behavior, and the metabolic syndrome in minority youth.
      ,
      • Chaput J.P.
      • Lambert M.
      • Mathieu M.E.
      • et al.
      Physical activity vs. sedentary time: independent associations with adiposity in children.
      ,
      • Martinez-Gomez D.
      • Eisenmann J.C.
      • Healy G.N.
      • et al.
      Sedentary behaviors and emerging cardiometabolic biomarkers in adolescents.
      ), the relationship between objectively measured sedentary time and health indicators is far less clear. Of the numerous studies examining the relationship between objectively measured sedentary time and markers of adiposity and cardiometabolic disease risk in the pediatric population (
      • Sardinha L.B.
      • Andersen L.B.
      • Anderssen S.A.
      • et al.
      Objectively measured time spent sedentary is associated with insulin resistance independent of overall and central body fat in 9- to 10-year-old Portuguese children.
      ,
      • Cliff D.P.
      • Okely A.D.
      • Burrows T.L.
      • et al.
      Objectively measured sedentary behavior, physical activity, and plasma lipids in overweight and obese children.
      ,
      • Colley R.C.
      • Garriguet D.
      • Janssen I.
      • et al.
      The association between accelerometer-measured patterns of sedentary time and health risk in children and youth: a cross-sectional study.
      ,
      • Mitchell J.A.
      • Pate R.R.
      • Beets M.W.
      • et al.
      Time spent in sedentary behavior and changes in childhood BMI: a longitudinal study from ages 9 to 15 years.
      ,
      • Chaput J.P.
      • Saunders T.J.
      • Mathieu M.E.
      • et al.
      Combined associations between moderate to vigorous physical activity and sedentary behavior with cardiometabolic risk factors in children.
      ,
      • Henderson M.
      • Gray-Donald K.
      • Mathieu M.E.
      • et al.
      How are physical activity, fitness, and sedentary behavior associated with insulin sensitivity in children?.
      ,
      • Kriska A.
      • Delahanty L.
      • Edelstein S.
      • et al.
      Sedentary behavior and physical activity in youth with recent onset of type 2 diabetes.
      ,
      • Chaput J.P.
      • Lambert M.
      • Mathieu M.E.
      • et al.
      Physical activity vs. sedentary time: independent associations with adiposity in children.
      ,
      • Martinez-Gomez D.
      • Eisenmann J.C.
      • Healy G.N.
      • et al.
      Sedentary behaviors and emerging cardiometabolic biomarkers in adolescents.
      ,
      • Basterfield L.
      • Pearce M.S.
      • Adamson A.J.
      • et al.
      Physical activity, sedentary behavior, and adiposity in English children.
      ,
      • Martinez-Gomez D.
      Associations between sedentary behavior and blood pressure in young children.
      ,
      • Kwon S.
      • Burns T.L.
      • Levy S.M.
      • et al.
      Which contributes more to childhood adiposity: high levels of sedentarism or low levels of moderate-through-vigorous physical activity? The Iowa Bone Development Study.
      ,
      • Atkin A.J.
      • Ekelund U.
      • Møller N.C.
      • et al.
      Sedentary time in children: influence of accelerometer processing on health relations.
      ,
      • Mitchell J.A.
      • Mattocks C.
      • Ness A.R.
      • et al.
      Sedentary behavior and obesity in a large cohort of children.
      ,
      • Steele R.M.
      • van Sluijs E.M.F.
      • Cassidy A.
      • et al.
      Targeting sedentary time or moderate- and vigorous-intensity activity: independent relations with adiposity in a population-based sample of 10-y-old British children.
      ,
      • Ekelund U.
      • Luan J.
      • Sherar L.B.
      • et al.
      Moderate to vigorous physical activity and sedentary time and cardiometabolic risk factors in children and adolescents.
      ), only a small number (
      • Mitchell J.A.
      • Pate R.R.
      • Beets M.W.
      • et al.
      Time spent in sedentary behavior and changes in childhood BMI: a longitudinal study from ages 9 to 15 years.
      ,
      • Henderson M.
      • Gray-Donald K.
      • Mathieu M.E.
      • et al.
      How are physical activity, fitness, and sedentary behavior associated with insulin sensitivity in children?.
      ,
      • Atkin A.J.
      • Ekelund U.
      • Møller N.C.
      • et al.
      Sedentary time in children: influence of accelerometer processing on health relations.
      ) have detected associations that remained significant after adjustment for physical activity (Table). These findings raise questions about the health impact of sitting per se, in comparison to the impact of specific screen-based sedentary behaviours.
      TableComparison of reports examining the association between objectively measured sedentary time and markers of adiposity and cardiometabolic disease risk among children and youth
      ReferenceSetting

      (population)
      AgeN (M/F)AccelerometerSedentary cut-pointKey findings
      No significant associations reported
      Colley et al
      • Colley R.C.
      • Garriguet D.
      • Janssen I.
      • et al.
      The association between accelerometer-measured patterns of sedentary time and health risk in children and youth: a cross-sectional study.
      Canada

      (general population)
      6–19 years1608 (809/799)Actical<100 CPMSedentary time was not associated with BMI, waist circumference, HDL-cholesterol or systolic or diastolic blood pressure independent of age, wear time and MVPA.
      Carson and Janssen
      • Carson V.
      • Janssen I.
      Volume, patterns, and types of sedentary behavior and cardio-metabolic health in children and adolescents: a cross-sectional study.
      USA

      (general population)
      6–19 years2527 (1284/1243)ActiGraph AM-7124<100 CPMSedentary time was not associated with clustered cardiometabolic risk after adjustment for age, sex, race, SES, smoking, total fat, saturated fat, cholesterol and sodium, or after additional adjustment for MVPA.
      Martinez-Gomez et al
      • Martinez-Gomez D.
      • Eisenmann J.C.
      • Healy G.N.
      • et al.
      Sedentary behaviors and emerging cardiometabolic biomarkers in adolescents.
      Spain

      (general population)
      13–17 years183 (95/88)ActiGraph GT1M<100 CPMSedentary time was not associated with CRP, adiponectin or other adipokines after adjustment for sex, age, and pubertal status, or after further adjustment for BMI and MVPA.
      Kwon et al
      • Kwon S.
      • Burns T.L.
      • Levy S.M.
      • et al.
      Which contributes more to childhood adiposity: high levels of sedentarism or low levels of moderate-through-vigorous physical activity? The Iowa Bone Development Study.
      USA

      (general population)
      8–15 years554 (277/277)ActiGraph 7164<100 CPMSedentary time was not associated with fat mass after adjustment for height and MVPA.
      Chaput et al
      • Chaput J.P.
      • Lambert M.
      • Mathieu M.E.
      • et al.
      Physical activity vs. sedentary time: independent associations with adiposity in children.
      Canada

      (children with a family history of obesity)
      8–11 years550 (299/251)ActiGraph LS 7164<100 CPMSedentary time was not associated with body fat percentage or waist-to-height ratio with or without adjustment for age, sex, sleep duration, energy intake, sexual maturation, parental SES and BMI or MVPA.
      Martinez-Gomez et al
      • Martinez-Gomez D.
      Associations between sedentary behavior and blood pressure in young children.
      US

      (general population)
      3–8 years111 (57/54)ActiGraph 7164<100 CPMSedentary time was not associated with systolic or diastolic blood pressure after adjustment for age, sex, height or body fat percentage.
      Significant associations reported for at least one outcome, not independent of physical activity
      Sardinha et al
      • Sardinha L.B.
      • Andersen L.B.
      • Anderssen S.A.
      • et al.
      Objectively measured time spent sedentary is associated with insulin resistance independent of overall and central body fat in 9- to 10-year-old Portuguese children.
      Portugal

      (general population)
      9–10 years308 (161/147)MTI ActiGraph<500 CPMSedentary time positively associated with insulin resistance after adjustment for sex, sexual maturity, birth weight, measurement time and both total and central adiposity.
      Cliff et al
      • Cliff D.P.
      • Okely A.D.
      • Burrows T.L.
      • et al.
      Objectively measured sedentary behavior, physical activity, and plasma lipids in overweight and obese children.
      Australia

      (overweight and obese)
      5–10 years126ActiGraph 7164<100 CPMSedentary time was negatively associated with HDL cholesterol, but not triglycerides, total or LDL cholesterol after adjustment for age, sex, adiposity and diet. Sedentary time was not associated with any outcome after additional adjustment for MVPA.
      Kriska et al
      • Kriska A.
      • Delahanty L.
      • Edelstein S.
      • et al.
      Sedentary behavior and physical activity in youth with recent onset of type 2 diabetes.
      USA

      (youth with obesity and type 2 diabetes)
      10–18 years551ActiGraph AM7164<1 METObese youths with T2D were sedentary for 56 more minutes/day than obese youth without T2D.
      Ekelund et al
      • Ekelund U.
      • Luan J.
      • Sherar L.B.
      • et al.
      Moderate to vigorous physical activity and sedentary time and cardiometabolic risk factors in children and adolescents.
      UK, Switzerland, Belgium, US, Australia, Denmark, Estonia, Norway, Brazil, Portugal

      (general population)
      4–18 years20,870 (10,097/10,773)Various types of ActiGraph<100 CPMSedentary time was associated fasting insulin, but not waist circumference, systolic blood pressure, triglycerides or HDL cholesterol after adjustment for age, sex, wear time, waist circumference and height. Sedentary time was not associated with any outcome after further adjustment for MVPA.
      Chaput et al
      • Chaput J.P.
      • Saunders T.J.
      • Mathieu M.E.
      • et al.
      Combined associations between moderate to vigorous physical activity and sedentary behavior with cardiometabolic risk factors in children.
      Canada

      (children with a family history of obesity)
      8–11 years536 (292/244)ActiGraph LS 7164<100 CPMSedentary time was positively associated with diastolic blood pressure, but not waist circumference, triglycerides, systolic blood pressure, fasting glucose, or HDL cholesterol, after adjustment for age, sex, waist circumference, sleep duration, energy intake, sexual maturation, parental SES and BMI. Sedentary time was not associated with any outcome after further adjustment for MVPA.
      Basterfield et al
      • Basterfield L.
      • Pearce M.S.
      • Adamson A.J.
      • et al.
      Physical activity, sedentary behavior, and adiposity in English children.
      UK

      (general population)
      7–9 years377 (186/191)ActiGraph GT1M<1100 CPMChanges in sedentary time were associated with increased fat gain in the entire sample independent of SES, baseline sedentary time, and baseline fat mass index. This association was no longer significant after additional adjustment for MVPA.
      Mitchell et al
      • Mitchell J.A.
      • Mattocks C.
      • Ness A.R.
      • et al.
      Sedentary behavior and obesity in a large cohort of children.
      UK

      (general population)
      12 years5,434 (2,950/2,844)ActiGraph AM7164≤199 CPMSedentary time was significantly associated with increased risk of obesity independent gender, SES, pubertal status and early life sleep and TV habits. These associations were no longer significant after adjustment for MVPA.
      Steele et al
      • Steele R.M.
      • van Sluijs E.M.F.
      • Cassidy A.
      • et al.
      Targeting sedentary time or moderate- and vigorous-intensity activity: independent relations with adiposity in a population-based sample of 10-y-old British children.
      UK

      (general population)
      9–10 years1862 (820/1042)ActiGraph GT1M<100 CPMSedentary time was positively associated with waist circumference and fat mass index (but not BMI) in unadjusted analyses. Sedentary time remained associated with fat mass index after adjustment for age, sex, SES, birth weight, sleep duration or maternal BMI. Sedentary time was not associated with any outcome after further adjustment for MVPA.
      Hsu et al
      • Hsu Y.W.
      • Belcher B.R.
      • Ventura E.E.
      • et al.
      Physical activity, sedentary behavior, and the metabolic syndrome in minority youth.
      US8–19 years105 (26/79)ActiGraph GT1M<100 CPMSedentary time was positively associated with waist circumference and systolic blood pressure, but not triglycerides, fasting glucose, HDL cholesterol or diastolic blood pressure in unadjusted analyses. After adjustment for MVPA, sedentary time was not associated with any outcome.
      Significant associations reported for at least one outcome, independent of physical activity
      Henderson et al
      • Henderson M.
      • Gray-Donald K.
      • Mathieu M.E.
      • et al.
      How are physical activity, fitness, and sedentary behavior associated with insulin sensitivity in children?.
      Canada

      (children with a family history of obesity)
      8–11 years424 (222/202)ActiGraph LS 7164<100 CPMSedentary time was positively associated with insulin resistance after adjustment for sex, age, pubertal stage, fitness and MVPA, but not after additional adjustment for adiposity.
      Mitchell et al
      • Mitchell J.A.
      • Pate R.R.
      • Beets M.W.
      • et al.
      Time spent in sedentary behavior and changes in childhood BMI: a longitudinal study from ages 9 to 15 years.
      US

      (general population)
      9–15 years798 (391/407)ActiGraph 7164 and GTM1<100 CPMSedentary time was associated with weight gain the 50th, 75th and 90th BMI percentiles independent of sex, race, maternal education, hours of sleep, healthy eating scores, and MVPA. No significant associations were observed at lower BMI percentiles.
      Atkin et al
      • Atkin A.J.
      • Ekelund U.
      • Møller N.C.
      • et al.
      Sedentary time in children: influence of accelerometer processing on health relations.
      Denmark, Estonia and Portugal

      (general population)
      9, 15 years2327 (1,059/1,268)MTI ActiGraph<100, <500, <800, and <1100 CPMIn metaregression using data from all cutpoints, sedentary time was associated with increased clustered cardiometabolic disease risk (but not adiposity) independent of age group, age, sex, study location, sexual maturity, day of the week, season, wear time, adiposity and total physical activity. The relationship between sedentary time and clustered risk was stronger at higher accelerometry thresholds.
      BMI, body mass index; CPM, counts per minute; CRP, C-reactive protein; HDL, high-density lipoprotein; MET, MVPA, moderate and vigorous physical activity; SES, socioeconomic status; T1D, type 1 diabetes; T2D, type 2 diabetes.
      The differences between self-reported screen time and directly measured total sedentary time are most apparent when examined using a single cohort. For example, Carson and Janssen observed that self-reported TV viewing was independently associated with clustered cardiometabolic disease risk in a nationally representative sample of American children and youth (
      • Carson V.
      • Janssen I.
      Volume, patterns, and types of sedentary behavior and cardio-metabolic health in children and adolescents: a cross-sectional study.
      ). In contrast, the authors observed no independent associations between accelerometer-derived sedentary time and markers of cardiometabolic risk in the same sample. Similar findings have also been reported in other cohorts (
      • Chaput J.P.
      • Saunders T.J.
      • Mathieu M.E.
      • et al.
      Combined associations between moderate to vigorous physical activity and sedentary behavior with cardiometabolic risk factors in children.
      ,
      • Hsu Y.W.
      • Belcher B.R.
      • Ventura E.E.
      • et al.
      Physical activity, sedentary behavior, and the metabolic syndrome in minority youth.
      ,
      • Chaput J.P.
      • Lambert M.
      • Mathieu M.E.
      • et al.
      Physical activity vs. sedentary time: independent associations with adiposity in children.
      ,
      • Martinez-Gomez D.
      • Eisenmann J.C.
      • Healy G.N.
      • et al.
      Sedentary behaviors and emerging cardiometabolic biomarkers in adolescents.
      ,
      • Martinez-Gomez D.
      Associations between sedentary behavior and blood pressure in young children.
      ). Chaput and colleagues found that self-reported screen time (but not objectively measured total sedentary time) was independently associated with increased waist circumference and reduced HDL cholesterol concentrations in a cohort of 536 children at risk for obesity (
      • Chaput J.P.
      • Saunders T.J.
      • Mathieu M.E.
      • et al.
      Combined associations between moderate to vigorous physical activity and sedentary behavior with cardiometabolic risk factors in children.
      ). Similarly, Martinez-Gomez et al (
      • Martinez-Gomez D.
      • Eisenmann J.C.
      • Healy G.N.
      • et al.
      Sedentary behaviors and emerging cardiometabolic biomarkers in adolescents.
      ) reported that several biomarkers were independently and deleteriously associated with self-reported TV viewing, but not with objectively measured sedentary time, in a group of Spanish adolescents.
      Given the bias and error that are known to be associated with self-report measures (
      • Adamo K.B.
      • Prince S.A.
      • Tricco A.C.
      • et al.
      A comparison of indirect versus direct measures for assessing physical activity in the pediatric population: a systematic review.
      ,
      • Saunders T.J.
      • Prince S.A.
      • Tremblay M.S.
      Clustering of children's activity behaviour: the use of self-report versus direct measures.
      ), it is somewhat surprising that self-reported screen time appears to be more closely associated with health indicators than objective measures of total sedentary time such as accelerometry. It is not uncommon for studies to report levels of self-reported screen time that seem highly implausible (
      • Saunders T.J.
      • Prince S.A.
      • Tremblay M.S.
      Clustering of children's activity behaviour: the use of self-report versus direct measures.
      ,
      • Jago R.
      • Fox K.R.
      • Page A.S.
      • et al.
      Physical activity and sedentary behaviour typologies of 10-11 year olds.
      ), a characteristic that has been observed in other forms of self-report data collection as well (
      • Huang T.T.
      • Howarth N.C.
      • Lin B.-H.
      • et al.
      Energy intake and meal portions: associations with BMI percentile in U.S. children.
      ). For example, a recent study found that groups of highly active and highly sedentary 10- to 11-year-old students self-reported an average of 13.9 hours per day of screen time, and another 5.9 hours of physical activity (
      • Saunders T.J.
      • Prince S.A.
      • Tremblay M.S.
      Clustering of children's activity behaviour: the use of self-report versus direct measures.
      ,
      • Jago R.
      • Fox K.R.
      • Page A.S.
      • et al.
      Physical activity and sedentary behaviour typologies of 10-11 year olds.
      ). If this were true, it would leave only 4.2 hours each day for eating, sleeping and attending school, which seems unlikely. It has also been noted that the association between self-reported and directly measured sedentary behaviour can be extremely small (
      • Colley R.C.
      • Wong S.L.
      • Garriguet D.
      • et al.
      Physical activity, sedentary behaviour and sleep in Canadian children: parent-report versus direct measures and relative associations with health risk.
      ,
      • Carson V.
      • Janssen I.
      Volume, patterns, and types of sedentary behavior and cardio-metabolic health in children and adolescents: a cross-sectional study.
      ). Carson and Janssen observed a correlation of just 0.08 between self-reported TV viewing and accelerometer-derived sedentary time in a nationally representative sample of American children and youth (
      • Carson V.
      • Janssen I.
      Volume, patterns, and types of sedentary behavior and cardio-metabolic health in children and adolescents: a cross-sectional study.
      ), suggesting little overlap between the 2 measures.
      There are a number of factors that could explain the differences observed between self- and proxy-reported screen time and objectively measured sedentary time in children and youth. Self-reports and proxy reports of sedentary behaviour typically provide information only about a single behaviour (a subset of total sedentary time), whereas objective measures of sedentary time provide global measures of time spent being sedentary. The 2 types of measures are, therefore, assessing different things (
      • Colley R.C.
      • Wong S.L.
      • Garriguet D.
      • et al.
      Physical activity, sedentary behaviour and sleep in Canadian children: parent-report versus direct measures and relative associations with health risk.
      ). For this reason, self-reported and proxy-reported sedentary behaviour typically account for far less total time than do objective measures; Colley et al found that parent-reported screen time was equivalent to only a third of total sedentary time assessed via accelerometry in a representative sample of Canadian children (
      • Colley R.C.
      • Wong S.L.
      • Garriguet D.
      • et al.
      Physical activity, sedentary behaviour and sleep in Canadian children: parent-report versus direct measures and relative associations with health risk.
      ). Given the highly sedentary nature of contemporary life (
      • Colley R.
      • Garriguet D.
      • Janssen I.
      • et al.
      Physical activity of Canadian children and youth: accelerometer results from the 2007 to 2009 Canadian Health Measures Survey.
      ,
      • Matthews C.E.
      • Chen K.Y.
      • Freedson P.S.
      • et al.
      Amount of time spent in sedentary behaviors in the United States, 2003–2004.
      ,
      • Kwon S.
      • Burns T.L.
      • Levy S.M.
      • et al.
      Breaks in sedentary time during childhood and adolescence: Iowa bone development study.
      ,
      • Nettlefold L.
      • McKay H.A.
      • Warburton D.E.
      • et al.
      The challenge of low physical activity during the school day: at recess, lunch and in physical education.
      ,
      • Abbott R.A.
      • Straker L.M.
      • Mathiassen S.E.
      Patterning of children's sedentary time at and away from school.
      ), it has also been suggested that the weak associations seen between objective measures of sedentary behaviour and various health indicators in children and youth may be due to a lack of inter-individual variability (
      • Colley R.C.
      • Wong S.L.
      • Garriguet D.
      • et al.
      Physical activity, sedentary behaviour and sleep in Canadian children: parent-report versus direct measures and relative associations with health risk.
      ). Further, it has been noted that a variety of methods have been used to process accelerometer data in the pediatric population, and this may have a significant impact on the results of individual studies, making it difficult to compare directly results of separate investigations (
      • Cain K.L.
      • Sallis J.F.
      • Conway T.L.
      • et al.
      Using accelerometers in youth physical activity studies: a review of methods.
      ,
      • Atkin A.J.
      • Ekelund U.
      • Møller N.C.
      • et al.
      Sedentary time in children: influence of accelerometer processing on health relations.
      ). For example, studies have excluded data as “non-wear” time when there are as few as 10 (
      • Sardinha L.B.
      • Andersen L.B.
      • Anderssen S.A.
      • et al.
      Objectively measured time spent sedentary is associated with insulin resistance independent of overall and central body fat in 9- to 10-year-old Portuguese children.
      ,
      • Martinez-Gomez D.
      • Eisenmann J.C.
      • Healy G.N.
      • et al.
      Sedentary behaviors and emerging cardiometabolic biomarkers in adolescents.
      ) or as many as 100 (
      • Atkin A.J.
      • Ekelund U.
      • Møller N.C.
      • et al.
      Sedentary time in children: influence of accelerometer processing on health relations.
      ) consecutive minutes with accelerometer values of 0 CPM. Further, although an accelerometer threshold of 100 CPM is used most commonly to identify sedentary behaviour, thresholds as high as 1100 CPM have been used in studies examining the relationship between sedentary time and markers of adiposity and cardiometabolic risk in the pediatric age group (
      • Atkin A.J.
      • Ekelund U.
      • Møller N.C.
      • et al.
      Sedentary time in children: influence of accelerometer processing on health relations.
      ). Although the impact of such methodologic issues is not certain, a recent report by Atkin et al (
      • Atkin A.J.
      • Ekelund U.
      • Møller N.C.
      • et al.
      Sedentary time in children: influence of accelerometer processing on health relations.
      ) suggested that discrepancies in sedentary thresholds (e.g. 100 CPM vs. 1100 CPM) are likely to have a much larger impact than differences in non-wear time. Counterintuitively, the same authors reported that higher thresholds, which therefore classify higher intensities of movement as sedentary time, resulted in stronger associations between sedentary time and markers of cardiometabolic disease risk in the pediatric population. Further research into the impact of such methodologic issues and techniques for comparing across studies employing different methodologies is clearly warranted.
      Finally, as discussed below, it is also possible that certain forms of sedentary behaviour (e.g. TV viewing and other forms of screen time) may disproportionately promote other unhealthy behaviours, such as excess food intake, which may explain why they are more consistently associated with health risk in the pediatric population (

      Saunders TJ. Potential contributors to the Canadian pediatric obesity epidemic. ISRN Pediatr vol 2011, Article ID 917684, 2011. http://dx.doi.org/10.5402/2011/917684.

      ,
      • Saunders T.J.
      • Chaput J.P.
      Is obesity prevention as simple as turning off the television and having a nap?.
      ). Taken together, these findings suggest that screen time (and especially TV viewing time [
      • Rey-López J.P.
      • Vicente-Rodríguez G.
      • Biosca M.
      • et al.
      Sedentary behaviour and obesity development in children and adolescents.
      ]) may be more closely associated with markers of cardiometabolic disease risk than total objectively measured sedentary time in the pediatric population, and this reinforces the notion that researchers should collect data using both measures whenever possible (
      • Lubans D.R.
      • Hesketh K.
      • Cliff D.P.
      • et al.
      A systematic review of the validity and reliability of sedentary behaviour measures used with children and adolescents.
      ,
      • Colley R.C.
      • Wong S.L.
      • Garriguet D.
      • et al.
      Physical activity, sedentary behaviour and sleep in Canadian children: parent-report versus direct measures and relative associations with health risk.
      ).

      Characteristics of sedentary behaviour: impact on health indicators

      In addition to the health impact of total sedentary time and specific sedentary behaviours (e.g. screen time), recent evidence in adults suggests that certain patterns of sedentary behaviour may also have an important health impact (
      • Healy G.N.
      • Dunstan D.W.
      • Salmon J.
      • et al.
      Breaks in sedentary time: beneficial associations with metabolic risk.
      ,
      • Healy G.N.
      • Matthews C.E.
      • Dunstan D.W.
      • et al.
      Sedentary time and cardio-metabolic biomarkers in US adults: NHANES 2003-06.
      ,

      Saunders TJ, Larouche R, Colley RC, et al. Acute sedentary behaviour and markers of cardiometabolic risk: a systematic review of intervention studies. J Nutr Metab vol. 2012, Article ID 712435, 2012. http://dx.doi.org/10.1155/2012/712435.

      ,
      • Dunstan D.W.
      • Kingwell B.A.
      • Larsen R.
      • et al.
      Breaking up prolonged sitting reduces postprandial glucose and insulin responses.
      ). A recent systematic review (

      Saunders TJ, Larouche R, Colley RC, et al. Acute sedentary behaviour and markers of cardiometabolic risk: a systematic review of intervention studies. J Nutr Metab vol. 2012, Article ID 712435, 2012. http://dx.doi.org/10.1155/2012/712435.

      ) concluded that prolonged bouts of uninterrupted sedentary behaviour have a rapid and deleterious impact on insulin sensitivity, glucose tolerance and triglyceride levels in adults. Further, interruptions in sedentary time have been shown to be beneficially associated with body weight, abdominal fat, triglycerides and glucose metabolism in adults (
      • Healy G.N.
      • Dunstan D.W.
      • Salmon J.
      • et al.
      Breaks in sedentary time: beneficial associations with metabolic risk.
      ,
      • Healy G.N.
      • Matthews C.E.
      • Dunstan D.W.
      • et al.
      Sedentary time and cardio-metabolic biomarkers in US adults: NHANES 2003-06.
      ,
      • Dunstan D.W.
      • Kingwell B.A.
      • Larsen R.
      • et al.
      Breaking up prolonged sitting reduces postprandial glucose and insulin responses.
      ). These findings have yet to be replicated in the pediatric population.
      Carson and Janssen failed to detect any associations between breaks in sedentary time or sedentary bout length and cardiometabolic disease risk in a nationally representative sample of 2527 American children and youth after adjustment for potential confounders (
      • Carson V.
      • Janssen I.
      Volume, patterns, and types of sedentary behavior and cardio-metabolic health in children and adolescents: a cross-sectional study.
      ). Kwon et al (
      • Kwon S.
      • Burns T.L.
      • Levy S.M.
      • et al.
      Breaks in sedentary time during childhood and adolescence: Iowa bone development study.
      ) also reported no association between breaks in sedentary time and fat mass in a sample of 544 boys and girls in the Iowa Bone Development Study, with similar findings being reported in children from the Pacific Islands (
      • Oliver M.
      • Schluter P.J.
      • Healy G.N.
      • et al.
      Associations between breaks in sedentary time and body size in pacific mothers and their children: findings from the pacific islands families study.
      ). To our knowledge, only 1 study to date has reported an association between characteristics of sedentary time and health indicators in children and youth; Colley and colleagues found that prolonged bouts of sedentary behaviour (those lasting 80+ minutes) are positively associated with waist circumference in boys aged 11 to 14 years in the Canadian Health Measures Survey, whereas the opposite is true for breaks in sedentary time (
      • Colley R.C.
      • Garriguet D.
      • Janssen I.
      • et al.
      The association between accelerometer-measured patterns of sedentary time and health risk in children and youth: a cross-sectional study.
      ). However, these associations were not observed in older or younger boys or in girls of any age.
      The limited evidence available to date suggests that characteristics of sedentary behaviour may be less closely associated with cardiometabolic disease risk in children than has been reported previously in adults. However, it should be noted that the studies that have been published to date have focused primarily on nationally representative samples of children and youth (
      • Colley R.C.
      • Garriguet D.
      • Janssen I.
      • et al.
      The association between accelerometer-measured patterns of sedentary time and health risk in children and youth: a cross-sectional study.
      ,
      • Carson V.
      • Janssen I.
      Volume, patterns, and types of sedentary behavior and cardio-metabolic health in children and adolescents: a cross-sectional study.
      ). It is possible that associations between characteristics of sedentary behaviour and cardiometabolic disease risk may be stronger in populations with family histories of obesity; this has previously been associated with increased childhood cardiometabolic risk (
      • Boney C.M.
      • Verma A.
      • Tucker R.
      • et al.
      Metabolic syndrome in childhood: association with birth weight, maternal obesity, and gestational diabetes mellitus.
      ,
      • Druet C.
      • Dabbas M.
      • Baltakse V.
      • et al.
      Insulin resistance and the metabolic syndrome in obese French children.
      ,
      • Reilly J.J.
      • Armstrong J.
      • Dorosty A.R.
      • et al.
      Early life risk factors for obesity in childhood: cohort study.
      ).

      Mechanisms by which sedentary behaviour can lead to poor health outcomes in children and youth

      A number of mechanisms have been suggested that could explain the reported associations between sedentary behaviour and cardiometabolic disease risk in the pediatric population. Sedentary behaviours are defined by their low energy expenditure, and it has historically been assumed that they displace physical activity (
      • Sedentary Behaviour Research Network
      Standardized use of the terms “sedentary” and “sedentary behaviours” [letter to the editor].
      ). This view is supported by a recent randomized crossover study that observed that exposing children to several hours of prolonged sitting did not result in any changes in physical activity levels in the subsequent 24-hour period (

      Saunders TJ, Chaput JP, Goldfield GS, et al. Children and youth do not compensate for an imposed bout of prolonged sitting by reducing subsequent food intake or increasing physical activity: a randomized crossover study. Br J Nutr (in press).

      ). This suggests that when children engage in a bout of prolonged sedentary behaviour, they do not compensate by increasing physical activity levels later on, thereby promoting positive energy balance (

      Saunders TJ, Chaput JP, Goldfield GS, et al. Children and youth do not compensate for an imposed bout of prolonged sitting by reducing subsequent food intake or increasing physical activity: a randomized crossover study. Br J Nutr (in press).

      ). However, other evidence suggests that the displacement of physical activity plays a relatively small role in mediating the relationship between sedentary time and cardiometabolic disease risk in children and youth (
      • Biddle S.J.
      • Gorely T.
      • Marshall S.J.
      • et al.
      Physical activity and sedentary behaviours in youth: issues and controversies.
      ,

      Saunders TJ. Potential contributors to the Canadian pediatric obesity epidemic. ISRN Pediatr vol 2011, Article ID 917684, 2011. http://dx.doi.org/10.5402/2011/917684.

      ,
      • Rey-López J.P.
      • Vicente-Rodríguez G.
      • Biosca M.
      • et al.
      Sedentary behaviour and obesity development in children and adolescents.
      ,
      • Marshall S.J.
      • Biddle S.J.H.
      • Gorely T.
      • et al.
      Relationships between media use, body fatness and physical activity in children and youth: a meta-analysis.
      ,
      • Grund A.
      • Krause H.
      • Siewers M.
      • et al.
      Is TV viewing an index of physical activity and fitness in overweight and normal weight children?.
      ). In a systematic review and meta-analysis examining the relationship between sedentary behaviours and physical activity, Marshall et al (
      • Marshall S.J.
      • Biddle S.J.H.
      • Gorely T.
      • et al.
      Relationships between media use, body fatness and physical activity in children and youth: a meta-analysis.
      ) reported that although the 2 are negatively associated, the magnitude of the relationship is too small to be of clinical significance. As noted above, numerous studies have also observed significant associations between sedentary behaviour (whether self-reported or directly measured) and markers of cardiometabolic disease risk independent of physical activity levels in the pediatric population (
      • Goldfield G.S.
      • Saunders T.J.
      • Kenny G.P.
      • et al.
      Screen viewing and diabetes risk factors in overweight and obese adolescents.
      ,
      • Goldfield G.S.
      • Kenny G.P.
      • Hadjiyannakis S.
      • et al.
      Video game playing is independently associated with blood pressure and lipids in overweight and obese adolescents.
      ,
      • Tremblay M.
      • LeBlanc A.G.
      • Kho M.
      • et al.
      Systematic review of sedentary behaviour and health indicators in school-aged children and youth.
      ,
      • Carson V.
      • Janssen I.
      Volume, patterns, and types of sedentary behavior and cardio-metabolic health in children and adolescents: a cross-sectional study.
      ). These findings suggest that a lack of physical activity is not the primary factor linking sedentary behaviour with health indicators in this age group.
      In contrast to a lack of physical activity, a number of studies suggest that screen-based sedentary behaviours may lead to increased caloric consumption through a variety of mechanisms (
      • Thivel D.
      • Aucouturier J.
      • Doucet E.
      • et al.
      Daily energy balance in children and adolescents: does energy expenditure predict subsequent energy intake?.
      ,
      • Pearson N.
      • Biddle S.J.
      Sedentary behavior and dietary intake in children, adolescents, and adults: a systematic review.
      ). A recent intervention by Harris et al (
      • Harris J.L.
      • Bargh J.A.
      • Brownell K.D.
      Priming effects of television food advertising on eating behavior.
      ) observed that exposing children to televised food advertisements increases subsequent ad libitum food intake by 45%. Similar results have also been reported by Halford and colleagues (
      • Halford J.C.
      • Gillespie J.
      • Brown V.
      • et al.
      Effect of television advertisements for foods on food consumption in children.
      ,
      • Halford J.C.
      • Boyland E.J.
      • Hughes G.
      • et al.
      Beyond-brand effect of television (TV) food advertisements/commercials on caloric intake and food choice of 5-7-year-old children.
      ), who reported that the impact of advertisements on increased food intake is seen across all body weight categories, although it is most pronounced in children with obesity (
      • Halford J.C.
      • Gillespie J.
      • Brown V.
      • et al.
      Effect of television advertisements for foods on food consumption in children.
      ). They also noted that the ability to recognize food advertisements was positively associated with food intake, and that children with overweight and obesity were more likely to remember food advertisements after being exposed to them, when compared to their lean peers (
      • Halford J.C.
      • Gillespie J.
      • Brown V.
      • et al.
      Effect of television advertisements for foods on food consumption in children.
      ). It is possible that television viewing may also result in increased food intake by inducing “mindless eating” (
      • Boulos R.
      • Vikre E.K.
      • Oppenheimer S.
      • et al.
      ObesiTV: How television is influencing the obesity epidemic.
      ). An intervention study by Temple et al (
      • Temple J.L.
      • Giacomelli A.M.
      • Kent K.M.
      • et al.
      Television watching increases motivated responding for food and energy intake in children.
      ) found that children spend more time eating and consume roughly twice as many calories while watching a continuous television program in comparison to a control condition without entertainment. Passive video-game playing has also been shown to increase food intake and result in a positive energy balance in the pediatric population. A randomized crossover study by Chaput et al (
      • Chaput J.P.
      • Visby T.
      • Nyby S.
      • et al.
      Video game playing increases food intake in adolescents: a randomized crossover study.
      ) observed that compared to sitting quietly, 1 hour of passive video game play resulted in an 80 kcal increase in ad libitum food intake in adolescent boys. The collective findings suggest that sedentary screen-based behaviours (in particular television viewing) are likely to result in increased energy intake and positive energy balance in the pediatric population.
      Finally, studies of adults suggest that prolonged sitting may have rapid and direct impacts on metabolic health, independent of changes in body weight or other health behaviours (
      • Tremblay M.S.
      • Colley R.C.
      • Saunders T.J.
      • et al.
      Physiological and health implications of a sedentary lifestyle.
      ,

      Saunders TJ, Larouche R, Colley RC, et al. Acute sedentary behaviour and markers of cardiometabolic risk: a systematic review of intervention studies. J Nutr Metab vol. 2012, Article ID 712435, 2012. http://dx.doi.org/10.1155/2012/712435.

      ). For example, intervention studies report that even relatively short bouts of uninterrupted sedentary behaviour result in reduced insulin sensitivity, glucose tolerance and increased triglyceride levels in adults (
      • Wilmot E.G.
      • Edwardson C.L.
      • Achana F.A.
      • et al.
      Sedentary time in adults and the association with diabetes, cardiovascular disease and death: systematic review and meta-analysis.
      ,

      Saunders TJ, Larouche R, Colley RC, et al. Acute sedentary behaviour and markers of cardiometabolic risk: a systematic review of intervention studies. J Nutr Metab vol. 2012, Article ID 712435, 2012. http://dx.doi.org/10.1155/2012/712435.

      ,
      • Dunstan D.W.
      • Kingwell B.A.
      • Larsen R.
      • et al.
      Breaking up prolonged sitting reduces postprandial glucose and insulin responses.
      ,
      • Stephens B.R.
      • Granados K.
      • Zderic T.W.
      • et al.
      Effects of 1 day of inactivity on insulin action in healthy men and women: interaction with energy intake.
      ,
      • Duvivier B.M.
      • Schaper N.C.
      • Bremers M.A.
      • et al.
      Minimal intensity physical activity (standing and walking) of longer duration improves insulin action and plasma lipids more than shorter periods of moderate to vigorous exercise (cycling) in sedentary subjects when energy expenditure is comparable.
      ). In comparison to a day of sitting that included periodic light-intensity walk breaks, Dunstan et al reported that a day of uninterrupted sitting resulted in a 30% increase in insulin resistance in a group of overweight and obese adults (
      • Dunstan D.W.
      • Kingwell B.A.
      • Larsen R.
      • et al.
      Breaking up prolonged sitting reduces postprandial glucose and insulin responses.
      ). Similar results have also been reported in normal-weight adults (
      • Stephens B.R.
      • Granados K.
      • Zderic T.W.
      • et al.
      Effects of 1 day of inactivity on insulin action in healthy men and women: interaction with energy intake.
      ,
      • Duvivier B.M.
      • Schaper N.C.
      • Bremers M.A.
      • et al.
      Minimal intensity physical activity (standing and walking) of longer duration improves insulin action and plasma lipids more than shorter periods of moderate to vigorous exercise (cycling) in sedentary subjects when energy expenditure is comparable.
      ) and may be due to reductions in lipoprotein lipase and glucose transport protein activity at the level of the skeletal muscles (
      • Hamilton M.T.
      • Hamilton D.G.
      • Zderic T.W.
      Role of low energy expenditure and sitting in obesity, metabolic syndrome, type 2 diabetes, and cardiovascular disease.
      ,
      • Tremblay M.S.
      • Colley R.C.
      • Saunders T.J.
      • et al.
      Physiological and health implications of a sedentary lifestyle.
      ).
      To date only 1 intervention study has examined the acute effect of prolonged sitting in a pediatric population. Saunders et al (
      • Saunders T.J.
      • Chaput J.P.
      • Goldfield G.S.
      • et al.
      Prolonged sitting and markers of cardiometabolic risk in children and youth: a randomized crossover study.
      ) exposed healthy 10- to 14-year-olds to a day of uninterrupted sitting, as well as days with periodic interruptions of light and moderate-intensity physical activity. In contrast to previous reports in adults (
      • Dunstan D.W.
      • Kingwell B.A.
      • Larsen R.
      • et al.
      Breaking up prolonged sitting reduces postprandial glucose and insulin responses.
      ), they reported that uninterrupted sitting did not have any impact on the insulin, glucose or lipid response to a standardized meal in this population. Although further intervention studies in children and youth are needed, the available evidence suggests that sitting per se may not have a direct deleterious impact on cardiometabolic health in healthy children and youth. Although it could be that the inherent metabolic health of children is such that current analytic methods have limited sensitivity to the detection of subtle, but adverse, physiologic changes.

      Opportunities for future research

      Although the relationship between certain sedentary behaviours (e.g. screen time) and cardiometabolic disease risk in children and youth are well established, the impact of sitting per se is far less clear. As discussed above, independent associations between objectively measured sedentary time and cardiometabolic risk have been reported by some but not all studies. More research is, therefore, needed to clarify the relationship between objectively measured sedentary behaviour and health indicators in the pediatric age group. Systematic reviews and meta-analyses focusing specifically on objectively measured sedentary behaviour (as opposed to previous reviews that have focused on all sedentary behaviours) may be especially useful in this regard. Standardization of accelerometry methodology would also allow for much easier comparisons across studies. Future research should also examine whether any personal factors, such as sex or body weight, influence the reporting of screen time and why some screen-based sedentary behaviours are associated with health outcomes in certain populations but not others (
      • Goldfield G.S.
      • Saunders T.J.
      • Kenny G.P.
      • et al.
      Screen viewing and diabetes risk factors in overweight and obese adolescents.
      ,
      • Goldfield G.S.
      • Kenny G.P.
      • Hadjiyannakis S.
      • et al.
      Video game playing is independently associated with blood pressure and lipids in overweight and obese adolescents.
      ).
      More research is also needed into the role played by specific characteristics of sedentary behaviour in the pediatric population. Only a small number of studies have investigated the impact of sedentary bout length or breaks in sedentary time in the pediatric population or the importance of sedentary behaviours during differing periods of the day (
      • Colley R.C.
      • Garriguet D.
      • Janssen I.
      • et al.
      The association between accelerometer-measured patterns of sedentary time and health risk in children and youth: a cross-sectional study.
      ,
      • Carson V.
      • Janssen I.
      Volume, patterns, and types of sedentary behavior and cardio-metabolic health in children and adolescents: a cross-sectional study.
      ). A better understanding of the characteristics of sedentary behaviour that are most closely associated with cardiometabolic disease risk is needed in order to develop interventions that are maximally efficacious in reducing cardiometabolic risk in children and youth. It is also possible that previously unexamined aspects of accelerometry data, such as total movement variability, may provide additional valuable information on movement patterns in the pediatric age group.
      Finally, intervention studies are needed to examine the health and behavioural impacts of prolonged sitting by the pediatric population. A recent systematic review concluded that uninterrupted sedentary behaviour results in rapid and deleterious changes in insulin sensitivity, glucose tolerance and lipid levels in adults (

      Saunders TJ, Larouche R, Colley RC, et al. Acute sedentary behaviour and markers of cardiometabolic risk: a systematic review of intervention studies. J Nutr Metab vol. 2012, Article ID 712435, 2012. http://dx.doi.org/10.1155/2012/712435.

      ). However, as noted above, these findings have yet to be replicated in children or youth (
      • Saunders T.J.
      • Chaput J.P.
      • Goldfield G.S.
      • et al.
      Prolonged sitting and markers of cardiometabolic risk in children and youth: a randomized crossover study.
      ). By extension, it is also unclear whether substituting sedentary behaviour for standing or light-intensity physical activity can lead to improvements in cardiometabolic disease risk in the pediatric population. Further research on the relationship between sedentary behaviours and sleep quality and quantity is also required, given the importance of a good night's sleep for overall health (
      • Knutson K.L.
      Sleep duration and cardiometabolic risk: a review of the epidemiologic evidence.
      ). Additionally, given the decline of outdoor active play observed over recent decades in children and youth (

      Active Healthy Kids Canada. Are we driving our kids to unhealthy habits? http://activehealthykids.ca/ReportCard/ReportCardOverview.aspx. Accessed May 21, 2013.

      ), more research is urgently needed to better understand the implications on children's health of excessive indoor time and its associated sedentary, technology-centered activities.

      Conclusions

      Available evidence suggests that North American children and youth spend between 40% and 60% of their waking hours engaging in sedentary behaviours (
      • Colley R.
      • Garriguet D.
      • Janssen I.
      • et al.
      Physical activity of Canadian children and youth: accelerometer results from the 2007 to 2009 Canadian Health Measures Survey.
      ,
      • Matthews C.E.
      • Chen K.Y.
      • Freedson P.S.
      • et al.
      Amount of time spent in sedentary behaviors in the United States, 2003–2004.
      ,
      • Pate R.R.
      • Mitchell J.A.
      • Byun W.
      • et al.
      Sedentary behaviour in youth.
      ). Markers of adiposity and cardiometabolic risk are positively associated with sedentary behaviours in general and with screen-based sedentary behaviours in particular. These relationships appear to be due to the influence of screen-based sedentary behaviours on food intake and may also be due to a direct metabolic impact of prolonged sitting, although this has received little research attention in the pediatric population. More research is needed to investigate the impacts of characteristics of sedentary behaviour (sedentary bout length, breaks in sedentary time, etc) and interventions that examine the health and behavioural impacts of sitting per se. Despite limited evidence in children and youth, reducing sedentary time in addition to increasing physical activity may have significant roles in the prevention of chronic diseases, including diabetes.

      Acknowledgements

      TJS is supported by a Doctoral Research Award from the Canadian Institutes of Health Research, a Doctoral Studentship Award from the Canadian Diabetes Association and an Excellence Scholarship from the University of Ottawa. JPC holds a Junior Research Chair in Healthy Active Living and Obesity Research. Some of the research reported in this review was supported by a Young Investigator's Award to JPC from the Children's Hospital of Eastern Ontario Research Institute.

      Author Disclosures

      No conflicts of interest were disclosed.

      Author Contributions

      The article was conceived and designed by TJS, JPC and MST. TJS wrote the initial draft of the manuscript, while MST and JPC provided critical edits and additions. All authors approved the final manuscript.

      References

        • Janssen I.
        • LeBlanc A.G.
        Systematic review of the health benefits of physical activity and fitness in school-aged children and youth.
        Int J Behav Nutr Phys Act. 2010; 7: 40
        • Andersen L.B.
        • Harro M.
        • Sardinha L.B.
        • et al.
        Physical activity and clustered cardiovascular risk in children: a cross-sectional study (The European Youth Heart Study).
        Lancet. 2006; 368: 299-304
        • Schmitz K.H.
        • Jacobs D.R.
        • Hong C.P.
        • et al.
        Association of physical activity with insulin sensitivity in children.
        Int J Obes. 2002; 26: 1310-1316
        • Sedentary Behaviour Research Network
        Standardized use of the terms “sedentary” and “sedentary behaviours” [letter to the editor].
        Appl Physiol Nutr Metab Physiol. 2012; 37: 540-542
        • Sardinha L.B.
        • Andersen L.B.
        • Anderssen S.A.
        • et al.
        Objectively measured time spent sedentary is associated with insulin resistance independent of overall and central body fat in 9- to 10-year-old Portuguese children.
        Diabetes Care. 2008; 31: 569-575
        • Danielsen Y.
        • Júlíusson P.
        • Nordhus I.
        • et al.
        The relationship between life-style and cardio-metabolic risk indicators in children: the importance of screen time.
        Acta Paediatr. 2011; 100: 253-259
        • Ekelund U.
        • Brage S.
        • Froberg K.
        • et al.
        TV viewing and physical activity are independently associated with metabolic risk in children: The European Youth Heart Study.
        PLOS Med. 2006; 3: e488
        • Mark A.E.
        • Janssen I.
        Relationship between screen time and metabolic syndrome in adolescents.
        J Public Health. 2008; 30: 153-160
        • Goldfield G.S.
        • Saunders T.J.
        • Kenny G.P.
        • et al.
        Screen viewing and diabetes risk factors in overweight and obese adolescents.
        Am J Prev Med. 2013; 44: S364-S370
        • Goldfield G.S.
        • Kenny G.P.
        • Hadjiyannakis S.
        • et al.
        Video game playing is independently associated with blood pressure and lipids in overweight and obese adolescents.
        PLOS ONE. 2011; 6: e26643
        • Tremblay M.S.
        • LeBlanc A.G.
        • Janssen I.
        • et al.
        Canadian sedentary behaviour guidelines for children and youth.
        Appl Physiol Nutr Metab. 2011; 36: 59-64
        • Cliff D.P.
        • Okely A.D.
        • Burrows T.L.
        • et al.
        Objectively measured sedentary behavior, physical activity, and plasma lipids in overweight and obese children.
        Obesity (Silver Spring). 2013; 21: 382-385
        • Hamilton M.T.
        • Hamilton D.G.
        • Zderic T.W.
        Role of low energy expenditure and sitting in obesity, metabolic syndrome, type 2 diabetes, and cardiovascular disease.
        Diabetes. 2007; 56: 2655-2667
        • Hamilton M.T.
        • Hamilton D.G.
        • Zderic T.W.
        Exercise physiology versus inactivity physiology: an essential concept for understanding lipoprotein lipase regulation.
        Exerc Sport Sci Rev. 2004; 32: 161-166
        • Tremblay M.S.
        • Colley R.C.
        • Saunders T.J.
        • et al.
        Physiological and health implications of a sedentary lifestyle.
        Appl Physiol Nutr Metab. 2010; 35: 725-740
        • Hamilton M.T.
        • Healy G.N.
        • Dunstan D.W.
        • et al.
        Too little exercise and too much sitting: inactivity physiology and the need for new recommendations on sedentary behavior.
        Curr Cardiovasc Risk Rep. 2008; 2: 292-298
        • Bergouignan A.
        • Rudwill F.
        • Simon C.
        • et al.
        Physical inactivity as the culprit of metabolic inflexibility: evidence from bed-rest studies.
        J Appl Physiol. 2011; 111: 1201-1210
        • Pate R.R.
        • O'Neill J.R.
        • Lobelo F.
        The evolving definition of “sedentary.”.
        Exerc Sport Sci Rev. 2008; 36: 173-178
        • Manson J.E.
        • Skerrett P.J.
        • Greenland P.
        The escalating pandemics of obesity and sedentary lifestyle: A call to action for clinicians.
        Arch Intern Med. 2004; 164: 249-258
        • Wilmot E.G.
        • Edwardson C.L.
        • Achana F.A.
        • et al.
        Sedentary time in adults and the association with diabetes, cardiovascular disease and death: systematic review and meta-analysis.
        Diabetologia. 2012; 55: 2895-2905
        • Lynch B.M.
        Sedentary behavior and cancer: a systematic review of the literature and proposed biological mechanisms.
        Cancer Epidemiol Biomarkers Prev. 2010; 19: 2691-2709
        • Lubans D.R.
        • Hesketh K.
        • Cliff D.P.
        • et al.
        A systematic review of the validity and reliability of sedentary behaviour measures used with children and adolescents.
        Obes Rev. 2011; 12: 781-799
        • Colley R.C.
        • Wong S.L.
        • Garriguet D.
        • et al.
        Physical activity, sedentary behaviour and sleep in Canadian children: parent-report versus direct measures and relative associations with health risk.
        Health Rep. 2012; 23: 45-52
        • Adamo K.B.
        • Prince S.A.
        • Tricco A.C.
        • et al.
        A comparison of indirect versus direct measures for assessing physical activity in the pediatric population: a systematic review.
        Int J Pediatr Obes. 2009; 4: 2-27
        • Prince S.A.
        • Adamo K.B.
        • Hamel M.E.
        • et al.
        A comparison of direct versus self-report measures for assessing physical activity in adults: a systematic review.
        Int J Behav Nutr Phys Act. 2008; 5: 56
        • Saunders T.J.
        • Prince S.A.
        • Tremblay M.S.
        Clustering of children's activity behaviour: the use of self-report versus direct measures.
        Int J Behav Nutr Phys Act. 2011; 8: 48
        • Biddle S.J.
        • Gorely T.
        • Marshall S.J.
        Is television viewing a suitable marker of sedentary behavior in young people?.
        Ann Behav Med. 2009; 38: 147-153
        • Sugiyama T.
        • Healy G.N.
        • Dunstan D.W.
        • et al.
        Is television viewing time a marker of a broader pattern of sedentary behavior?.
        Ann Behav Med. 2008; 35: 245-250
        • Cain K.L.
        • Sallis J.F.
        • Conway T.L.
        • et al.
        Using accelerometers in youth physical activity studies: a review of methods.
        J Phys Act Health. 2013; 10: 437-450
        • Treuth M.S.
        • Schmitz K.H.
        • Catellier D.
        • et al.
        Defining accelerometer thresholds for activity intensities in adolescent girls.
        Med Sci Sports Exerc. 2004; 36: 1259-1266
        • Evenson K.R.
        • Catellier D.J.
        • Gill K.
        • et al.
        Calibration of two objective measures of physical activity for children.
        J Sports Sci. 2008; 26: 1557-1565
        • Ridgers N.D.
        • Salmon J.
        • Ridley K.
        • et al.
        Agreement between activPAL and ActiGraph for assessing children's sedentary time.
        Int J Behav Nutr Phys Act. 2012; 9: 15
        • Trost S.G.
        • Pate R.R.
        • Sallis J.F.
        • et al.
        Age and gender differences in objectively measured physical activity in youth.
        Med Sci Sports Exerc. 2002; 34: 350-355
        • Trost S.G.
        • Loprinzi P.D.
        • Moore R.
        • et al.
        Comparison of accelerometer cut points for predicting activity intensity in youth.
        Med Sci Sports Exerc. 2011; 43: 1360-1368
        • Puyau M.R.
        • Adolph A.L.
        • Vohra F.A.
        • et al.
        Prediction of activity energy expenditure using accelerometers in children.
        Med Sci Sports Exerc. 2004; 36: 1625-1631
        • Wong S.L.
        • Colley R.
        • Connor-Gorber S.
        • et al.
        Actical accelerometer sedentary activity thresholds for adults.
        J Phys Act Health. 2011; 8: 587-591
        • Colley R.C.
        • Garriguet D.
        • Janssen I.
        • et al.
        The association between accelerometer-measured patterns of sedentary time and health risk in children and youth: a cross-sectional study.
        BMC Public Health. 2013 Mar 7; 13: 200https://doi.org/10.1186/1471-2458-13-200
        • Healy G.N.
        • Dunstan D.W.
        • Salmon J.
        • et al.
        Breaks in sedentary time: beneficial associations with metabolic risk.
        Diabetes Care. 2008; 31: 661-666
        • Healy G.N.
        • Matthews C.E.
        • Dunstan D.W.
        • et al.
        Sedentary time and cardio-metabolic biomarkers in US adults: NHANES 2003-06.
        Eur Heart J. 2011; 32: 590-597
        • Dowd K.P.
        • Harrington D.M.
        • Donnelly A.E.
        Criterion and concurrent validity of the Activpaltm professional physical activity monitor in adolescent females.
        PLOS ONE. 2012; 7: e47633
        • Aminian S.
        • Hinckson E.A.
        Examining the validity of the ActivPAL monitor in measuring posture and ambulatory movement in children.
        Int J Behav Nutr Phys Act. 2012; 9: 119
        • Colley R.
        • Garriguet D.
        • Janssen I.
        • et al.
        Physical activity of Canadian children and youth: accelerometer results from the 2007 to 2009 Canadian Health Measures Survey.
        Health Rep. 2011; 22: 15-24
        • Matthews C.E.
        • Chen K.Y.
        • Freedson P.S.
        • et al.
        Amount of time spent in sedentary behaviors in the United States, 2003–2004.
        Am J Epidemiol. 2008; 167: 875-881
        • Pate R.R.
        • Mitchell J.A.
        • Byun W.
        • et al.
        Sedentary behaviour in youth.
        Br J Sports Med. 2011; 45: 906-913
        • Trang N.H.
        • Hong T.K.
        • van der Ploeg H.P.
        • et al.
        Longitudinal sedentary behavior changes in adolescents in Ho Chi Minh City.
        Am J Prev Med. 2013; 44: 223-230
        • Brodersen N.H.
        • Steptoe A.
        • Boniface D.R.
        • et al.
        Trends in physical activity and sedentary behaviour in adolescence: ethnic and socioeconomic differences.
        Br J Sports Med. 2007; 41: 140-144
        • Kwon S.
        • Burns T.L.
        • Levy S.M.
        • et al.
        Breaks in sedentary time during childhood and adolescence: Iowa bone development study.
        Med Sci Sports Exerc. 2012; 44: 1075-1080
        • Schramm W.
        • Lyle J.
        • Parker E.
        Television in the lives of our children.
        Stanford University Press, Stanford, CA1961
        • Rideout V.
        • Foehr U.
        • Roberts D.
        Generation M2: Media in the lives of 8- to 18-year-olds.
        Kaiser Family Foundation, 2010 (Access May 14, 2013.)
        • Leatherdale S.T.
        • Ahmed R.
        Screen-based sedentary behaviours among a nationally representative sample of youth: are Canadian kids couch potatoes?.
        Chronic Dis Inj Can. 2011; 31: 141-146
        • Sigmundova D.
        • El Ansari W.
        • Sigmund E.
        • et al.
        Secular trends: a ten-year comparison of the amount and type of physical activity and inactivity of random samples of adolescents in the Czech Republic.
        BMC Public Health. 2011; 11: 731
        • Mak K.-K.
        • Day J.R.
        Secular trends of sports participation, sedentary activity and physical self-perceptions in Hong Kong adolescents, 1995-2000.
        Acta Paediatr. 2010; 99: 1731-1734
        • Cui Z.
        • Hardy L.L.
        • Dibley M.J.
        • et al.
        Temporal trends and recent correlates in sedentary behaviours in Chinese children.
        Int J Behav Nutr Phys Act. 2011; 8: 93
        • Øverby N.C.
        • Klepp K.-I.
        • Bere E.
        Changes in screen time activity in Norwegian children from 2001 to 2008: two cross-sectional studies.
        BMC Pub Health. 2013; 13: 80
      1. Australian Government Department of Health and Ageing. Sedentary behaviour and screen-time. http://www.health.gov.au/internet/publications/publishing.nsf/Content/gug-director-toc∼gug-sedentary. Accessed May 14, 2013.

        • Biddle S.J.
        • Gorely T.
        • Marshall S.J.
        • et al.
        Physical activity and sedentary behaviours in youth: issues and controversies.
        J R Soc Promot Health. 2004; 124: 29-33
      2. Silva KS, da Silva Lopes A, Dumith SC, et al. Changes in television viewing and computers/videogames use among high school students in Southern Brazil between 2001 and 2011. Int J Public Health (in press).

        • Buliung R.N.
        • Mitra R.
        • Faulkner G.
        Active school transportation in the Greater Toronto Area, Canada: an exploration of trends in space and time (1986-2006).
        Prev Med. 2009; 48: 507-512
        • McDonald N.C.
        Active transportation to school: trends among U.S. schoolchildren, 1969-2001.
        Am J Prev Med. 2007; 32: 509-516
        • Van der Ploeg H.P.
        • Merom D.
        • Corpuz G.
        • et al.
        Trends in Australian children traveling to school 1971-2003: burning petrol or carbohydrates?.
        Prev Med. 2008; 46: 60-62
        • Tremblay M.
        • LeBlanc A.G.
        • Kho M.
        • et al.
        Systematic review of sedentary behaviour and health indicators in school-aged children and youth.
        Int J Behav Nutr Phys Act. 2011; 8: 98
        • Hernández B.
        • Gortmaker S.L.
        • Colditz G.A.
        • et al.
        Association of obesity with physical activity, television programs and other forms of video viewing among children in Mexico city.
        Int J Obes Relat Metab Disord. 1999; 23: 845-854
        • Kaur H.
        • Choi W.S.
        • Mayo M.S.
        • et al.
        Duration of television watching is associated with increased body mass index.
        J Pediatr. 2003; 143: 506-511
        • Mitchell J.A.
        • Pate R.R.
        • Beets M.W.
        • et al.
        Time spent in sedentary behavior and changes in childhood BMI: a longitudinal study from ages 9 to 15 years.
        Int J Obes. 2013; 37: 54-60
        • Robinson T.N.
        Reducing children's television viewing to prevent obesity: a randomized controlled trial.
        JAMA. 1999; 282: 1561-1567
        • Epstein L.H.
        • Roemmich J.N.
        • Robinson J.L.
        • et al.
        A randomized trial of the effects of reducing television viewing and computer use on body mass index in young children.
        Arch Pediatr Adolesc Med. 2008; 162: 239-245
      3. Saunders TJ. Potential contributors to the Canadian pediatric obesity epidemic. ISRN Pediatr vol 2011, Article ID 917684, 2011. http://dx.doi.org/10.5402/2011/917684.

        • Chaput J.P.
        • Saunders T.J.
        • Mathieu M.E.
        • et al.
        Combined associations between moderate to vigorous physical activity and sedentary behavior with cardiometabolic risk factors in children.
        Appl Physiol Nutr Metab. 2013; 38: 477-483
        • Henderson M.
        • Gray-Donald K.
        • Mathieu M.E.
        • et al.
        How are physical activity, fitness, and sedentary behavior associated with insulin sensitivity in children?.
        Diabetes Care. 2012; 35: 1272-1278
        • Carson V.
        • Janssen I.
        Volume, patterns, and types of sedentary behavior and cardio-metabolic health in children and adolescents: a cross-sectional study.
        BMC Pub Health. 2011; 11: 274
        • Kriska A.
        • Delahanty L.
        • Edelstein S.
        • et al.
        Sedentary behavior and physical activity in youth with recent onset of type 2 diabetes.
        Pediatrics. 2013; 131: e850-e856
        • Wennberg P.
        • Gustafsson P.E.
        • Dunstan D.W.
        • et al.
        Television viewing and low leisure-time physical activity in adolescence independently predict the metabolic syndrome in mid-adulthood.
        Diabetes Care. 2013; 36: 2090-2097
        • Hsu Y.W.
        • Belcher B.R.
        • Ventura E.E.
        • et al.
        Physical activity, sedentary behavior, and the metabolic syndrome in minority youth.
        Med Sci Sports Exerc. 2011; 43: 2307-2313
        • Chaput J.P.
        • Lambert M.
        • Mathieu M.E.
        • et al.
        Physical activity vs. sedentary time: independent associations with adiposity in children.
        Pediatr Obes. 2012; 7: 251-258
        • Martinez-Gomez D.
        • Eisenmann J.C.
        • Healy G.N.
        • et al.
        Sedentary behaviors and emerging cardiometabolic biomarkers in adolescents.
        J Pediatr. 2012; 160: 104-110
        • Basterfield L.
        • Pearce M.S.
        • Adamson A.J.
        • et al.
        Physical activity, sedentary behavior, and adiposity in English children.
        Am J Prev Med. 2012; 42: 445-451
        • Martinez-Gomez D.
        Associations between sedentary behavior and blood pressure in young children.
        Arch Pediatr Adolesc Med. 2009; 163: 724-730
        • Kwon S.
        • Burns T.L.
        • Levy S.M.
        • et al.
        Which contributes more to childhood adiposity: high levels of sedentarism or low levels of moderate-through-vigorous physical activity? The Iowa Bone Development Study.
        J Pediatr. 2013; 162: 1169-1174
        • Atkin A.J.
        • Ekelund U.
        • Møller N.C.
        • et al.
        Sedentary time in children: influence of accelerometer processing on health relations.
        Med Sci Sports Exerc. 2012; 45: 1097-1104
        • Mitchell J.A.
        • Mattocks C.
        • Ness A.R.
        • et al.
        Sedentary behavior and obesity in a large cohort of children.
        Obesity (Silver Spring). 2009; 17: 1596-1602
        • Steele R.M.
        • van Sluijs E.M.F.
        • Cassidy A.
        • et al.
        Targeting sedentary time or moderate- and vigorous-intensity activity: independent relations with adiposity in a population-based sample of 10-y-old British children.
        Am J Clin Nutr. 2009; 90: 1185-1192
        • Ekelund U.
        • Luan J.
        • Sherar L.B.
        • et al.
        Moderate to vigorous physical activity and sedentary time and cardiometabolic risk factors in children and adolescents.
        JAMA. 2012; 307: 704-712
        • Jago R.
        • Fox K.R.
        • Page A.S.
        • et al.
        Physical activity and sedentary behaviour typologies of 10-11 year olds.
        Int J Behav Nutr Phys Act. 2010; 7: 59
        • Huang T.T.
        • Howarth N.C.
        • Lin B.-H.
        • et al.
        Energy intake and meal portions: associations with BMI percentile in U.S. children.
        Obes Res. 2004; 12: 1875-1885
        • Nettlefold L.
        • McKay H.A.
        • Warburton D.E.
        • et al.
        The challenge of low physical activity during the school day: at recess, lunch and in physical education.
        Br J Sports Med. 2011; 45: 813-819
        • Abbott R.A.
        • Straker L.M.
        • Mathiassen S.E.
        Patterning of children's sedentary time at and away from school.
        Obesity (Silver Spring). 2013; 21: e131-e133
        • Saunders T.J.
        • Chaput J.P.
        Is obesity prevention as simple as turning off the television and having a nap?.
        Br J Nutr. 2012; 108: 946-947
        • Rey-López J.P.
        • Vicente-Rodríguez G.
        • Biosca M.
        • et al.
        Sedentary behaviour and obesity development in children and adolescents.
        Nutr Metab Cardiovasc Dis. 2008; 18: 242-251
      4. Saunders TJ, Larouche R, Colley RC, et al. Acute sedentary behaviour and markers of cardiometabolic risk: a systematic review of intervention studies. J Nutr Metab vol. 2012, Article ID 712435, 2012. http://dx.doi.org/10.1155/2012/712435.

        • Dunstan D.W.
        • Kingwell B.A.
        • Larsen R.
        • et al.
        Breaking up prolonged sitting reduces postprandial glucose and insulin responses.
        Diabetes Care. 2012; 35: 976-983
        • Oliver M.
        • Schluter P.J.
        • Healy G.N.
        • et al.
        Associations between breaks in sedentary time and body size in pacific mothers and their children: findings from the pacific islands families study.
        J Phys Act Health. 2013; 10: 1166-1174
        • Boney C.M.
        • Verma A.
        • Tucker R.
        • et al.
        Metabolic syndrome in childhood: association with birth weight, maternal obesity, and gestational diabetes mellitus.
        Pediatrics. 2005; 115: e290-e296
        • Druet C.
        • Dabbas M.
        • Baltakse V.
        • et al.
        Insulin resistance and the metabolic syndrome in obese French children.
        Clin Endocrinol. 2006; 64: 672-678
        • Reilly J.J.
        • Armstrong J.
        • Dorosty A.R.
        • et al.
        Early life risk factors for obesity in childhood: cohort study.
        BMJ. 2005; 330: 1357
      5. Saunders TJ, Chaput JP, Goldfield GS, et al. Children and youth do not compensate for an imposed bout of prolonged sitting by reducing subsequent food intake or increasing physical activity: a randomized crossover study. Br J Nutr (in press).

        • Marshall S.J.
        • Biddle S.J.H.
        • Gorely T.
        • et al.
        Relationships between media use, body fatness and physical activity in children and youth: a meta-analysis.
        Int J Obes Relat Metab Disord. 2004; 28: 1238-1246
        • Grund A.
        • Krause H.
        • Siewers M.
        • et al.
        Is TV viewing an index of physical activity and fitness in overweight and normal weight children?.
        Public Health Nutr. 2001; 4: 1245-1251
        • Thivel D.
        • Aucouturier J.
        • Doucet E.
        • et al.
        Daily energy balance in children and adolescents: does energy expenditure predict subsequent energy intake?.
        Appetite. 2013; 60: 58-64
        • Pearson N.
        • Biddle S.J.
        Sedentary behavior and dietary intake in children, adolescents, and adults: a systematic review.
        Am J Prev Med. 2011; 41: 178-188
        • Harris J.L.
        • Bargh J.A.
        • Brownell K.D.
        Priming effects of television food advertising on eating behavior.
        Health Psychol. 2009; 28: 404-413
        • Halford J.C.
        • Gillespie J.
        • Brown V.
        • et al.
        Effect of television advertisements for foods on food consumption in children.
        Appetite. 2004; 42: 221-225
        • Halford J.C.
        • Boyland E.J.
        • Hughes G.
        • et al.
        Beyond-brand effect of television (TV) food advertisements/commercials on caloric intake and food choice of 5-7-year-old children.
        Appetite. 2007; 49: 263-267
        • Boulos R.
        • Vikre E.K.
        • Oppenheimer S.
        • et al.
        ObesiTV: How television is influencing the obesity epidemic.
        Physiol Behav. 2012; 107: 146-153
        • Temple J.L.
        • Giacomelli A.M.
        • Kent K.M.
        • et al.
        Television watching increases motivated responding for food and energy intake in children.
        Am J Clin Nutr. 2007; 85: 355-361
        • Chaput J.P.
        • Visby T.
        • Nyby S.
        • et al.
        Video game playing increases food intake in adolescents: a randomized crossover study.
        Am J Clin Nutr. 2011; 93: 1196-1203
        • Stephens B.R.
        • Granados K.
        • Zderic T.W.
        • et al.
        Effects of 1 day of inactivity on insulin action in healthy men and women: interaction with energy intake.
        Metabolism. 2011; 60: 941-949
        • Duvivier B.M.
        • Schaper N.C.
        • Bremers M.A.
        • et al.
        Minimal intensity physical activity (standing and walking) of longer duration improves insulin action and plasma lipids more than shorter periods of moderate to vigorous exercise (cycling) in sedentary subjects when energy expenditure is comparable.
        PLOS ONE. 2013; 8: e55542
        • Saunders T.J.
        • Chaput J.P.
        • Goldfield G.S.
        • et al.
        Prolonged sitting and markers of cardiometabolic risk in children and youth: a randomized crossover study.
        Metabolism. 2013; 62: 1423-1428
        • Knutson K.L.
        Sleep duration and cardiometabolic risk: a review of the epidemiologic evidence.
        Best Pract Res Clin Endocrinol Metab. 2010; 24: 731-743
      6. Active Healthy Kids Canada. Are we driving our kids to unhealthy habits? http://activehealthykids.ca/ReportCard/ReportCardOverview.aspx. Accessed May 21, 2013.