Setting an earlier bedtime for your children could help keep their weight in check, a new study finds.

Fast food, too much screen time, and sugary sodas are not the only factors to blame for the childhood obesity epidemic, experts say. Lack of sleep is also an important factor, the findings show.

Scientists from Temple University in Philadelphia enlisted 37 children aged eight to 11, with more than a quarter of the subjects being overweight or obese.

The first week of the study, the children slept their normal amount. During the second week, the children randomly had their sleep time reduced or lengthened. And in the third week, they were given the opposite sleep schedule.

Findings showed that when children slept longer, they ate around 134 fewer calories per day and lost half a pound in weight.

"Findings from this study suggest that enhancing school-age children's sleep at night could have important implications for prevention and treatment of obesity," said head researcher Dr. Chantelle Hart, from Temple University in Philadelphia. "The potential role of sleep should be further explored."

The findings were published online November 4 in the journal Pediatrics.

A separate study on adults published earlier this year found that a lack of sleep causes changes in brain activity that can lead people to feel hungrier and crave more fattening foods.

A team from the University of California used MRI (magnetic resonance imaging) scans to spot changes in the brain activity of sleep-deprived test subjects. Those findings appear in the journal Nature Communications.