Getting enough rest at night not only helps kids feel rested and alert; it contributes to better health as well. But a recent study suggests that when children sleep can also impact health and physical activity levels. A study of 9- to 16-year-old Australians found that adolescents who were “early to bed and early to rise” were less likely to be obese than night owls who woke up later. Night owls logged 2.9 times more television and computer screen time. They also replaced about 30 minutes of physical activity with 30 minutes of inactivity, compared with early sleepers. Sleep duration was more or less the same for both groups.

“The children who went to bed late and woke up late and the children who went to bed early and woke up early got virtually the same amount of sleep,” said co-author Carol Maher, PhD, in a press release. “Scientists have realized in recent years that children who get less sleep tend to do worse on a variety of health outcomes, including the risk of being overweight and obese. Our study suggests that the timing of sleep is even more important.”

The study was published in the October 1 issue of SLEEP (2011; 34 [10], 1299–1307).