From San Diego, at the Experimental Biology 2003 meeting

Plenty of recent studies have chronicled an epidemic of obesity in the United States. Although adults have been chided for not exercising enough, many researchers have blamed the growing girth of adolescents on their love of junk food and soft drinks. Now, an analysis of government data on teens’ health concludes that most obesity in adolescents, as in their elders, traces to insufficient physical activity.

Before conducting the study, nutritionist Lisa A. Sutherland of the University of North Carolina in Chapel Hill was puzzled, she says. Although national data indicated runaway obesity in young people, several studies suggested that calorie intake among teens has remained fairly constant. So, she plumbed 20 years of data on some 3,400 children, age 12 to 19, from a U.S. Department of Agriculture program known as the Continuing Survey of Food Intakes by Individuals. The results confirmed that over the past 2 decades, teens’ calorie consumption has risen only 1 percent. Over that same period, others have reported, the prevalence of overweight U.S. teens has nearly tripled–to 15 percent.

For a measure of youthful activity, Sutherland consulted data on 12,400 teens collected by the Centers for Disease Control and Prevention. On the basis of self-reports, the numbers showed a 13 percent drop in physical activity during the past 2 decades. By 2000, Sutherland found, just 29 percent said they exercise regularly.

She now plans to probe gender differences in teens’ exercise and eating habits. She hopes to make people aware of the implications of cutbacks by schools in physical education requirements and to figure out what interventions might be needed to compensate for teens’ reduced activity.


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Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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