There was a research article in the January issue of Pediatrics about sleep duration and obese children. The authors studied children aged 4 to 10 years old. They measured their body mass index (BMI) and sleep patterns with a home device called actigraphy.
The children averaged 8 hours of sleep per night during the school week, regardless of BMI. Of note, the recommended number of hours of sleep for children those ages is between 10-13 hours. So right off the bat, these kids are sleep-deprived.
On the weekends, children with high BMI's (meaning obesity) tended to sleep shorter duration and have a more irregular sleep pattern than normal-weight kids. The authors interpreted this to mean that obese children did not catch up on sleep as well as thinner kids. The children who slept less and more irregular also had higher levels of insulin, bad cholesterol, and C-reactive protein (associated with heart disease). The authors explain that sleep deprivation is associated with hormonal changes that can increase appetite.
I don't know if the children were matched for other factors like socio-economic status and family history, which could affect weight regardless of sleep duration or sleep pattern.
I wonder if the irregular sleep pattern and shorter sleep duration on the weekends reflects lack of limit-setting of the parents, which could explain obesity more than sleep duration. As I have said in a previous post, childhood obesity is not caused by lack of sleep. Sleep could play a small part, but our children's diet and lack of exercise are the overwhelming contributors.