Food, Sleep and Obesity.

A study of New Zealand seven-year-olds has found that sleeping fewer than nine hours a night is associated with being overweight or obese, even after accounting for time spent watching television, and physical exercise.
"The study is important from the perspective of providing another means of preventing obesity," said Ed Mitchell, the senior author and a professor of child health research at Auckland University... Sleeping more than nine hours and 45 minutes lowered the risk significantly.

... and no mention of food intake??

Strikes me that if you stay up later you are more likely to have a snack before going to bed.
Now when I was a young fella, and it was important to put on weight to get in to that higher grade rugby team, a decent feed before bed was a 'fail safe' procedure.

Correlation studies do not show causal relationships ... unfortunately such studies will probably result in unnecessary 'parental forcings' ... "Go to bed now and go to sleep." ... with the resultant objections, refusals and tantrums ... and I always believed that most lost their 'puppy fat' in their mid to late teens - probably something to do with rapid growth, activity levels and eating less as a means of enhancing marketability.