Other studies indicate that poor sleep can throw off the body's biological clocks -- also known as circadian rhythms -- particularly the clock that regulates glucose and insulin, two hormones that when out of balance, are closely associated with weight gain, heart disease and diabetes. Sleep deficit has also been found to elevate levels of cortisol, a hormone that among other things regulates how the body uses energy; elevated cortisol levels have been linked to insulin resistance and a higher BMI.
Beyond metabolic disruptions, many experts believe that part of the problem is what kids are doing when they're not tucked between the sheets: They're watching TV, playing video games and chowing down on high-calorie junk foods, activities associated with higher childhood obesity rates.
However, not all experts agree that catch-up sleep can help in the fight against childhood obesity. "I'm not sure what definite conclusions can come from a study that lasted only one week but I do think the connection between getting enough sleep and obesity may be there. As far as catch-up sleep on the weekend, other studies have shown the opposite, that you are much better off staying on same schedule including the weekend to keep your circadian rhythms steady and consistent," said Dr. Vicky McEvoy, chief of pediatrics at Mass General West Medical School in Boston.
Gozal said that as a first pass on an important issue, the Pediatrics study is by far the most thorough and extensive to date. "Other studies have only looked at two or three days. This study took place during school year versus summer vacation and reflects the majority of time a child is engaged in typical activities. It's also the first to show an inconsistency between weekday and weekend sleep and we were able to at least pick up suggestion to that effect."
Regardless of weight category, the average child in the study slept eight hours a night during the week – far less than the nine to10 hours recommended by the National Institutes of Health and other health groups. And that's really the take-home message Gonzal wants parents to hear.
"Clearly sleeping is a good healthy proposition and our recommendation is to make every possible effort to have a regular bedtime schedule for your child. Adequate sleep can help reduce obesity as well as other health problems like cardiovascular disease and diabetes now and in the future."