Posted by Amy Jordan 
Research published in this monthâs issue of the journal Obesity offers strong evidence of yet one more piece of the puzzle of childhood overweight: too little sleep. Parents already know that children who go to bed late end up as cranky little monsters the next day; but they should also know that consistent sleep deficits pack on extra pounds in youngsters. The report, published by researchers at Johns Hopkins University, pulled together 17 studies on sleep and childhood obesity from around the world and found the pattern of data to be consistent: children who donât get enough sleep are significantly more likely to be overweight. Specifically, for each hour increase in sleep, the risk of overweight was reduced by nine percent.
Why is sleep related to weight? These Hopkins authors, and others, have some hypotheses. First, it may be that overtired kids are more likely to reach for a sugary snack that will give them a boost when their energy lags. (That seems to be what happens for adults.) Second, kids who stay up later have more opportunity to snack, and their snack choices are probably not healthy ones. Finally, sleep deficits may affect certain hormones which, according to the authors of the study, increase childrenâs feelings of hunger and decrease their energy expenditures.
The expert panel on childhood overweight, which I co-chaired with my Stanford colleague Tom Robinson, recommends that parents avoid putting a television set in childrenâs bedrooms. Based on the Hopkins team findings, this recommendation may be very important. Research done at the Annenberg Public Policy Center found that children with bedroom television sets spend more time watching television than children without them. It could well be that a key reason why children in these studies are going to bed too late is that they are using media: not just watching television shows and movies but also playing videogames and going online with their computers. This is an empirical question, however: What are children staying up late doing with their time? New research is needed that looks not only at the connection between bedroom TVs and computers but examines the link between having these screen media so readily available and its impact on the quality and quantity of sleep. That may be one more explanation for why excessive screen time is linked to overweight, an explanation that takes us beyond the sedentary nature of viewing, the exposure of kids to junk food advertising, and the snacking that tends to occur while viewing.
So what can parents do to help avoid the sleep deficit/weight problem trap? Most health professionals recommend that children younger than 5 get at least 11 hours of sleep, children between 5 and 10 get at least 10 hours of sleep, and adolescents over 10 strive for 9 hours or more. Since most school aged children have fixed wake up times, getting children to bed earlier will be key. This means that children should begin winding down 30-60 minutes before climbing into bed. Their transition time from wakefulness to sleep should not be assisted by television, videogame or computer use, which many experts feel charge kids up rather than help them relax. Replacing media time with quality parent-child time will likely yield benefits for childrenâs physical health, and will also strengthen family bonds and childrenâs emotional well-being.
Amy Jordan is senior research investigator and director of the Media and the Developing Child sector of the Annenberg Public Policy Center of the University of Pennsylvania.
