Reduced physical activity not linked to increased obesity in teens

Washington: Reduced physical activity may do little in explaining the increase in obesity rates among US adolescents, according to a study.

Researchers at the Johns Hopkins Bloomberg School of Public Health investigated concerns that the spike may be due to decreased physical activity linked with increased TV viewing time and other sedentary behaviours.

Senior author Youfa Wang, MD, PhD, MS, and associate professor with the Bloomberg School``s Center for Human Nutrition and the Department of International Health, found that the physical activity among adolescents increased while TV viewing decreased in recent years.

Wang said: "Although only one third of US adolescents met the recommended levels of physical activity, there is no clear evidence they had become less active over the past decade while the prevalence of obesity continued to rise.

"During the recent decade, US adolescents had greater access to TV, but significantly fewer of them watched TV for three or more hours per day.

“In addition, daily physical education attendance rates improved along with the use of physical education class in engaging in physical activity.

“However, there are considerable differences in the patterns by age, sex and ethnicity."

Wang, along with co-authors Shiru Li, MD, MS, former visiting scholar with the Bloomberg School``s Center for Human Nutrition, and Margarita Treuth, PhD, adjunct associate professor with the Bloomberg School``s Center for Human Nutrition and a professor with the University of Maryland East Shore, based their findings on the nationally representative Youth Risk Behavior Surveillance (YRBS) surveys from 1991 to 2007.

Wang revealed. "Our study suggests that more vigorous efforts are needed to help young Americans engage in adequate regular physical activity and reduce sedentary behaviors, which will help promote good health.

“In addition, these findings may suggest factors other than physical activity, and sedentary behaviors such as unhealthy eating may play a more important role to help explain the recent increase in obesity."

The study "How Active are American Adolescents and Have They Become Less Active" has been published in the online issue of Obesity Reviews.