A new study by researchers at the University of Michigan shows that children who get less than 9.75 hours of sleep in the third grade are 40 percent more likely to be overweight in the sixth grade (whether they were already overweight or not in the third grade). It was found that the longer the kids slept, the less the chance for obesity. It is already known that adults lacking sleep (less then 7 hours) are at increased risk for weight gain. The researchers believe this problem is caused by disruption of healthy leptin function, as well as disruption of one of leptin's companions, ghrelin (pronounced grel-an).