The more time a child spends in front of a screen, the lower his or her level of cardiovascular fitness is. Research has shown that children who had greater than four hours of screen time per day were less than half as likely to be physically fit as those who spent less than two hours in front of a screen per day. Moreover, this is not merely a function of children spending less time engaging in physical activity; even when physical activity was controlled for, spending greater than two hours per day in front of a screen for boys (four hours per day for girls) was associated with decreased chances of being fit (Ogunleye & Sandercock, 2013).
Increased Body Fat
There are three factors here. First, increased screen time has been associated with increased body fat in children because of decreased physical activity in children (Melkevik, Torsheim, Iannotti, & Wold 2010; Ogunleye & Sandercock 2011, 2012). The idea is that screen time is competing with time spent doing physical activity, and as a result, children have higher adiposity.
Secondly, increased screen time is associated with poorer eating habits. One study found the more screen time a child had, the lower his or her fruit and vegetable consumption, and, the higher his or her unhealthy snack and drink, fast food, and overall caloric intake was (Pearson & Biddle 2011). Another study shows that watching TV during meals, specifically, compounds this effect, leading to higher food intake by delaying satiation and reducing satiety signals from earlier meals (Bellissimo, Pencharz, Thomas, & Anderson, 2007). In other words, eating in front of the television causes children’s bodies not to register that they are full, and so they eat more.
Third, the processed food that is advertised contains chemicals that (a) fool the brain (excitotoxins that are addictive but harm neurons, like monosodium glutamate), (b) fool the tongue (impairing taste so that regular foods taste bad), and (c) fool the gut (artificial sweeteners cause the body to prepare for real sugar absorption at first but over time the body becomes confused and does not digest foods properly). (See here.)
With all this being said, screen time does not just lead to unhealthy habits that, in turn, cause increased adiposity. Screen time has actually been found to contribute independently to children’s weight status. Regardless of physical fitness, screen time predicts children’s body mass index (Ulrich-French, Power, Daratha, Bindler, & Steele, 2010).
Type II Diabetes
One study investigating insulin sensitivity in children found that screen time and insulin sensitivity are negatively associated in girls. In other words, the more time young girls spend in front of a screen, the lower their insulin sensitivity (Henderson, et al., 2012). Insulin is a hormone that functions to regulate the delivery of sugar to cells for use as energy. Insulin resistance is a condition in which cells can no longer respond to insulin (i.e. the cells have very low insulin sensitivity). This results in hyperglycemia, or high blood sugar, which puts high demand on the cells that produce insulin and can, in turn, cause type II diabetes (National Institute of Diabetes and Digestive and Kidney Diseases, 2013). Moreover, the associations discovered between screen time and insulin sensitivity are independent of body fat levels and physical fitness.
Increased screen time is also associated with higher blood pressure in children, regardless of weight status (Martinez-Gomez, Tucker, Heelan, Welk, & Eisenmann, 2009). Adolescents who met the AAP’s recommendation of two hours or less of screen time per weekday have significantly lower systolic blood pressures than those who exceed the two hour limit (Ulrich-French, Power, Daratha, Bindler, & Steele, 2010). Hypertension, or high blood pressure, is dangerous because it makes the heart work too hard and can contribute to the hardening of arteries, called atherosclerosis, as well as increase the risk of heart disease and stroke (National Heart, Lung, and Blood Institute).
It is important to note that the increase in blood pressure associated with screen time is not simply a function of a sedentary lifestyle. One study demonstrated that the type of sedentary behavior makes a difference when it comes to increased blood pressure. Playing video games, watching TV, and engaging in other screen time activities all led to significantly increased blood pressure, but reading, on the other hand, was actually associated with significantly decreased blood pressure (Gopinath, et al., 2011).
Metabolic syndrome (MetS) is group of risk factors including several of the medical conditions already outlined above: high adiposity (body fat), increased blood pressure, and increased blood sugar levels. When all of these conditions occur together, they increase the risk of heart disease, stroke, and diabetes (National Heart, Lung, and Blood Institute).
Studies investigating the link between screen time and MetS have found that the likelihood of having MetS increases as screen time hours increase, regardless of physical activity. Adolescents who exceeded the AAP’s recommendation, reporting three or more hours of screen time per day, were at least two times more likely to have MetS than those that had less than one hour of screen time per day (Mark & Jannsen, 2008, see also Kang, Lee, Shim, Shin, Park, & Lee, 2010 for a similar study in Korean population). This research suggests not only that screen time impacts all of the previously mentioned health conditions, but also that, together, the individual effects of screen time on different body systems can combine to influence whether or not your child will develop chronic disease in adulthood.
Asthma is a chronic lung disease that inflames and narrows the airways, leading to recurring periods of wheezing, chest tightness, shortness of breath, and coughing (National Heart, Lung, and Blood Institute). Increased screen time has been linked with an increased risk of asthma. Children who have three or more hours of screen time per day almost double their risk of asthma. This is especially true for children who are obese. Once again, this association is independent of physical activity; physical activity was not found to predict asthma risk (Protudjer, Kozyrskyj, McGavock, Ramsey, & Becker, 2012).
Technology is playing a different, and bigger, role in all of our lives, including children’s, but that does not make the AAP’s recommendation outdated or irrelevant. In fact, the increasing role of technology in our lives should be all the more reason to pay close attention to recommendations like the AAP’s that suggested limited screen time for children (and probably for adults too!).
So…Next time you are tempted to let your child watch an extra hour of TV or play that videogame a little longer, you might want to reconsider and send them outside instead. Your decision could have an impact on your child’s habits and their overall physical health. If children consistently exceed the recommended two hour limit on screen time, they will be at increased risk for chronic illness in the future! Furthermore, an increase in physical activity is not enough to reverse these effects. Screen time impacts physical health independent of physical activity, so the best solution is simply to reduce screen time, and maybe go to the library and do paper book reading.
American Academy of Pediatrics Committee on Public Education. (2001). Children, Adolescents, and Television. Pediatrics, 107(2), 223-6.
Bellissimo, N., Pencharz, P.B., Thomas, S.G., & Anderson, G.H. (2007). Effect of Television Viewing at Mealtime on Food Intake After a Glucose Preload in Boys. Pediatrics Research, 61(6), 745-9.
Gopinath, B., Baur, L.A., Wang, J.J., Hardy, L.L., Teber, E., Kifley, A.,…,&Mitchell, P. (2011). Influence of Physical Activity and Screen Time on the Retinal Microvasculature in Young Children. Arteriosclerosis, Thrombosis, and Vascular Biology, 31, 1233-1239.
Henderson, M., Gray-Donald,K., Barnett, T.A., Hanley, J.A., O’Loughlin, J. …& Lambert, M.(2012). How Are Physical Activity, Fitness, and Sedentary Behavior Associated With Insulin Sensitivity in Children? Diabetes Care, 35,1272-1278.
Kang, H., Lee,H., Shim,J, Shin, Y., Park, B., & Lee, Y. (2010). Association between screen time and metabolic syndrome in children and adolescents in Korea: The 2005 Korean National Health and Nutrition Examination Survey. Diabetes Research and Clinical Practice, 89, 72-78.
Mark, A.E., & Janssen, I. (2008). Relationship between screen time and metabolic syndrome in adolescents. Journal of Public Health,30(2), 153-160.
Martinez-Gomez, D., Tucker, J., Heelan, K.A., Welk, G.J., & Eisenmann, J.C. (2009). Associations Between Sedentary Behavior and Blood Pressure in Young Children. Archives of Pediatrics and Adolescent Medicine, 163(8), 724-730.
Melkevik, O., Torsheim,T., Iannotti, R., & Wold, B. (2010). Is spending time in screen-based sedentary behaviors associated with less physical activity: a cross-national investigation. International Journal of Behavioral Nutrition and Physical Activity, 7(46), 1-10.
National Heart, Lung, and Blood Institute. (2013). What Are High Blood Pressure and Prehypertension? National Institute of Health. http://www.nhlbi.nih.gov/hbp/hbp/whathbp.htm
National Heart, Lung, and Blood Institute. (2013). What is Asthma? National Institute of Health. http://www.nhlbi.nih.gov/health/health-topics/topics/asthma/
National Heart, Lung, and Blood Institute. (2013). What is Metabolic Syndrome? National Institute of Health. http://www.nhlbi.nih.gov/health/health-topics/topics/ms/
National Institute of Diabetes and Digestive and Kidney Diseases (2013, Jan 22). Insulin Resistance and Prediabetes. National Diabetes Information Clearninghouse. http://diabetes.niddk.nih.gov/dm/pubs/insulinresistance/
Ogunleye, A.A., Voss, C., & Sandercock, G.R. (2011). Prevalence of high screen time in English youth: association with deprivation and physical activity. Journal of Public Health, 34(1), 46-53.
Pearson, N., & Biddle, J.H. (2011). Sedentary Behavior and Dietary Intake in Children, Adolescents, and Adults: A Systematic Review. American Journal of Preventative Medicine, 41(2), 178-88.
Protudjer, J., Kozyrskyj, A., McGavock, J.M., Ramsey, C.D., & Becker, A.B. (2012). High Screen Time Is Associated with Asthma in Overweight Manitoba Youth. Journal of Asthma, 49(9), 935-941.
Rothman, L. (2013, Nov 20). FYI, Parents: Your Kids Watch A Full-Time Job’s Worth of TV Each Week. Time. http://entertainment.time.com/2013/11/20/fyi-parents-your-kids-wa...
Sandercock, G.R.H., Ogunleye, A., & Voss,C. (2012). Screen Time and Physical Activity in Youth: Thief of Time or Lifestyle Choice? Journal of Physical Activity and Health, 9(7), 977-84.
Sandercock, G.R.H., & Ogunleye, A. (2013). Independence of physical activity and screen time as predictors of cardiorespiratory fitness in youth. Pediatric Research, 73(5), 692-697.
Ullrich-French, S.C., Power, T.G., Daratha, K.B., Bindler, R.C., & Steele, M.M. (2010). Examination of adolescents’ screen time and physical fitness as independent correlates of weight status and blood pressure. Journal of SportsSciences, 28(11), 1189-96.
*Rebecca Noble is a student at the University of Notre Dame, Indiana, USA.
BLOG SERIES ON PLAY
1 Happiness and Growth Through Play
2 Playing with Heart
3 Children May Be Playing, But Their Brains Are Working
4 Is Pretend Play Good For Kids?
5 Playing at School: More Important Than We Thought?
6 Does Too Much Screen Time Make Kids Sick?
7 Infant Couch Potatoes
8 What's Better: Indoor or Outdoor Play?
9 Why Play with a Child?