There was an article by NPR about a recent study published in the Archives of Pediatric and Adolescent Medicine. The researchers surveyed 2000 children about their sleep duration and measured the children's weight over a five year period.
The researchers concluded that children who slept greater than 10 hours per night were less obese than those that slept less than 10 hours per night. Napping during the daytime did not help, implying that nighttime sleep duration is the more important factor. The effect was most prominent in infants and toddlers. The authors of the study hypothesized that children who do not get enough sleep would be too tired to exercise. Also, certain hormones that control appetite can be affected by sleep duration, but this has only been proven in adults.
The article author at NPR lead off the story by stating that in infants and pre-schoolers, a good and long nights sleep may be just as important as diet and physical activity with regards to obesity! This is highly misleading, in my opinion. It takes the focus off the real problem with childhood obesity, which is their poor diet. If it only were that easy - just get more sleep and your overweight child will be thin again. The problem with this study is that it is dependent on parents' report of sleep duration, which is frought with uncertainty. Also, it could be argued that parents who let their children stay up late probably also let them eat too much junk food. I wish the authors of the study had surveyed caloric intake along with sleep duration in these children.
Don't get me wrong. Sleep is very important to kids' physical, emotional, and cognitive development. And too little sleep could play a small role in weight regulation. But lets focus on the real problem with childhood obesity rather than on these minor issues.