Trends in physical activity, sedentary behavior, diet, and BMI among US adolescents, 2001-2009

The high prevalence of adolescent obesity in the United States has been attributed to population changes in physical activity (PA), sedentary behaviors, and dietary behaviors. This study examines 8-year trends in these behaviors in US adolescents ages 11 to 16.

Nationally representative samples of US students in grades 6 to 10 were recruited during the 2001-2002 (N = 14607), 2005-2006 (N = 9150), and 2009-2010 (N = 10848) school years by using multistage stratified designs, with census regions and grades as strata, and school districts as the primary sampling units. African-American and Hispanic students were oversampled to obtain better estimates for those groups. Using the Health Behavior in School-aged Children quadrennial surveys, identical questions assessed BMI, PA, and sedentary and dietary behaviors at each school year. Logistic and linear regression analyses were conducted taking into account the sampling design and controlling for age, gender, race/ethnicity, and family affluence.

Across the quadrennial surveys, significant increases were identified in number of days with at least 60 minutes of PA, daily consumption of fruits and vegetables, eating breakfast on weekdays and weekends, and BMI. Television viewing and consumption of sweets and sweetened beverages decreased across this same period. These same patterns were seen in all racial/ethnic groups.

These patterns suggest that public health efforts to improve the obesity-related behaviors of US adolescents may be having some success. However, alternative explanations for the increase in BMI over the same period need to be considered.