One-fourth of overweight children may have sleep problems that regular physical activity can largely resolve, researchers say.

Research published in the November issue of Obesity shows a surprising 25 out of 100 overweight, inactive children tested positive for sleep-disordered breathing, including telltale snoring.

After about three months of vigorous after-school physical activity such as jumping rope, basketball and tag games, the number of children who tested positive for a sleep disorder was cut in half, according to lead researcher, Dr. Catherine L. Davis. In children who exercised the longest, the number was reduced by 80 percent.

The children were among 100 black and white boys and girls ages 7 to 11 enrolled in a study looking at the effect of exercise on metabolism. For the purposes of that study, the children were divided into three groups: a control group as well as those who exercised 20 or 40 minutes daily.

In fact researchers found the average score for all children who exercised – even those who did not test positive for sleep disorders – improved on the Pediatric Sleep Questionnaire.

"Existing data suggests about two percent of children have sleep problems but with 37 percent of children now considered overweight, the percentage may be much higher," says Dr. Davis, clinical health psychologist at the Medical College of Georgia and the study's first author.

"We believe this study is a red flag to pediatricians to ask parents about their children's snoring," she says. "Snoring does not appear to be benign in children. Not sleeping well can affect children's behavior, their ability to function in school. We don't know yet if it affects their development."