Children who are physically active have better body-fat distribution regardless of their weight, according to a recent study.

Researchers from the University of Illinois found that healthy-weight kids should not get a pass on exercising.

"The FITKids study demonstrates the extent to which physical activity can improve body composition, and that's important because it matters to your health where fat is stored. But the study is also interesting for what happened in the control group to the kids who didn't exercise," Naiman Khan, a postdoctoral researcher in the University of Illinois's Division of Nutritional Sciences, said in a statement.

For the study, researchers recruited more than 200 8- and 9-year-old children and assigned them to either a nine-month physical activity intervention or a control group. The intervention provided 70 minutes of moderate to vigorous physical activity five days a week. Baseline and follow-up cardiorespiratory fitness, percent fat mass, percent central fat mass, and estimated abdominal fat tissue were measured.

Although the control group displayed no change in cardiorespiratory fitness, kids in that group increased in percent fat mass and abdominal fat tissue, Khan said.

"So the weight of healthy-weight children who don't exercise doesn't just remain stable. Normal-weight kids who don't exercise do gain an excess amount of weight for their age, and if they become overweight, the tendency is to store excess fat in their abdomens. They're going in the wrong direction," Khan noted.

Researchers said parents should promote exercise so their kids can avoid the onset of obesity.

"Your child should engage in moderate to vigorous exercise for about an hour a day. Adults should make sure kids have a space to play and play games in and opportunities to be physically during or after school. If kids are at a healthy weight for their age, we want to make sure they stay that way," Khan said.