An important component of a healthy lifestyle is physical activity. Unfortunately, physical activity declines substantially during adolescence. This is particularly true among adolescent girls, 48 percent of whom report low levels of physical activity by the time they are in the 12th grade. Adolescent girls are less likely than adolescent boys to participate in physical activity. Overweight adolescent girls are at an even greater risk for low levels of physical activity. To develop interventions to prevent this decline in physical activity among adolescent girls, it is important to understand the factors that affect activity levels in this group. In a comprehensive review of the studies published on this topic, the only conclusion that could be drawn was that more studies are needed. Most of the studies assessed information on population-based samples of adolescents and did not examine the issues over time. Neumark-Sztainer and associates evaluated the factors associated with changes in physical activity levels in adolescent girls at risk for sedentary lifestyles and obesity.

This cohort study examined the impact of a school-based obesity prevention physical education program on adolescent girls at six high schools. The schools were randomized into three intervention and three control schools. Girls in the intervention group were enrolled in the New Moves program, which consisted of five days per week of education, including physical activity, for 16 weeks. Adolescent girls with low levels of physical activity and girls who were in the precontemplation, contemplation, or preparation stage for change in physical activity were selected for participation. The program consisted of physical activity, nutritional guidance, and social support. The nonintervention group received minimal information about healthy eating and physical activity. Each group was assessed at baseline, postintervention, and at follow-up eight months later. The assessment included information concerning physical activity and variables from the personal, behavior, and socioenvironmental domains.

The authors enrolled 201 high school girls in the study, with 90 girls in the intervention group. The strongest and most consistent factors for change were time constraints and support for physical activity from peers, parents, and teachers. In addition, self-worth with regard to physical activity was associated with change in activity levels. A decrease in the perceived time constraints could result in an average increase of 53 minutes of moderate to vigorous physical activity per week. An increase in perceived support for physical activity could result in an average increase of 35 minutes per week, and an improvement in self-worth could result in an average increase of 19 minutes per week of moderate to vigorous physical activity.

The authors conclude that interventions aimed at increasing the rate of physical activity among adolescent girls might be made more effective by developing support from friends, families, and caring adults; addressing real and perceived time constraints; and improving girls' confidence in their ability to engage in physical activity. If these factors are addressed, the interventions may have a better chance at success.

editor's note: The alarming increase in the rate of obesity among children and adolescents is a major health concern in the United States. The majority of these persons will likely continue to be obese into their adult years and develop obesity-related diseases. To help physicians who care for children understand the issues related to obesity in this age group, the August 2003 issue of Archives of Pediatric and Adolescent Medicine was dedicated to this subject. This journal made it obvious that childhood obesity is a multifactorial problem and requires physicians, families, caring adults, and peers of obese children and adolescents to join the ranks in treating what some are calling an epidemic.—K.E.M.