Decreased physical activity may have little to do with the recent spike in obesity rates among U.S. adolescents, according to researchers at the Johns Hopkins Bloomberg School of Public Health. Prompted by growing concern that the increase was due to decreased physical activity associated with increased TV viewing time and other sedentary behaviors, researchers examined the patterns and time trends in physical activity and sedentary behaviors among U.S. adolescents based on nationally representative data collected since 1991. The review found signs indicating that the physical activity among adolescents increased while TV viewing decreased in recent years. The results are featured in the October 30 online issue of Obesity Reviews.
"Although only one third of U.S. 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," said Youfa Wang, MD, PhD, MS, senior author of the study and an associate professor with the Bloomberg School's Center for Human Nutrition and the Department of International Health. "During the recent decade, U.S. 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."