Exercise Key to Teen Weight Problem

Exercise may be the key to keeping the pounds off adolescents and may help overweight children reverse some of the harm caused by being fat, two teams of researchers reported.

The studies bolster the argument that children in rich countries need to get more exercise. In the United States, some 15 percent of children under age 19 are overweight, and many are starting to develop weight-related diseases such as type-II diabetes and heart disease.

A study of more than 850 southern California teenagers and younger children showed that just a bit of vigorous exercise made the difference between being of normal weight and being overweight.

On average, the children with normal weight had four minutes more of vigorous exercise over a single day than the overweight children, the team at the University of California San Diego found.

"This might be an indicator of a more active lifestyle generally," Dr. Kevin Patrick, a professor of family and preventive medicine who led the study, said in a telephone interview.

Children who ate more fruits and vegetables also were less likely to be overweight, Patrick's team found, and fiber intake better predicted who would be overweight than fat intake did.

"Insufficient physical activity and too much time spent on sedentary behaviors like computer games and watching TV may equal, and even exceed, diet quality as important contributors to overweight in adolescence," Patrick said.

In fact, the normal-weight children consumed slightly more calories than the overweight children, but apparently burned them off, Patrick's team said in the April issue of the American Medical Association's Archives of Pediatric and Adolescent Medicine.

Patrick's team chose 878 children age 11 to 15 registered at six San Diego County clinics. They found that nearly half of the children were at risk for becoming overweight or were already overweight by standard measures.

They questioned the children carefully, asked them to write down everything they ate in food diaries, and attached devices to measure how much exercise they got over a day.

They analyzed the group by age, sex, ethnic group, sedentary behavior, vigorous exercise, household income and diet. Of all these measures, only exercise clearly predicted which children would be overweight, Patrick said.

VASCULAR ABNORMALITIES

In the second study, a team at The Chinese University of Hong Kong studied 54 boys and 28 girls with an average age of just under 10. All were either overweight or obese.

At age 9, tests of their blood vessel function "matched those of a 45-year-old adult who had been smoking for more than 10 years," said Dr. Kam Woo, who led the study.

"We were surprised that the children had developed vascular abnormalities at such a young age -- and by how readily these could be reversed with simple lifestyle measures," said Woo, whose study is published in this week's issue of the American Heart Association journal Circulation.

All the children met with a dietitian twice a week and followed a 900- to 1,200-calorie diet that was low in fat and high in fruits, vegetables and whole grains.

Some children were led by a trainer through a 75-minute program twice a week that included aerobics and other exercises.

After six weeks, all the children narrowed their waists, lowered their cholesterol and had healthier arteries. But the blood vessel improvement was more marked in those who exercised.

After a year, the children who stuck with the exercise program had a major improvement in one measure of heart disease risk -- the thickness of the carotid artery, the researchers said. They also had less body fat and lower cholesterol levels.