The effectiveness of interventions to increase physical activity among adolescent girls: a meta-analysis.

BACKGROUND Research has shown that a clear decline in physical activity among girls starting in early adolescence. Therefore, adolescent girls have been identified as a key target population for physical activity behavior change. The quantification of intervention effectiveness for this group has not been previously reported in a meta-analysis, and this therefore was the objective of the current meta-analysis. STUDY SELECTION Included were interventions in which the main component, or 1 of the components, was aimed at promoting physical activity through behavior change in any setting. Interventions had to include a non-physical activity control group or comparison group, and include a quantitative outcome assessment of physical activity behavior in girls aged 12 to 18 years. DATA SOURCES Science Direct, PubMed, PsychINFO, Web of Science, Cochrane Libraries, and EPPI Centre databases were searched up to and including May 2013. DATA EXTRACTION AND SYNTHESIS Forty-five studies (k = 34 independent samples) were eligible from an initial 13,747 references. A random-effects meta-analysis was conducted. RESULTS The average treatment effect for adolescent girls involved in physical activity interventions was significant but small (g = 0.350, 95% confidence interval 0.12, 0.58, P < .001). Moderator analyses showed larger effects for interventions that were theory based, performed in schools, were girls only, with younger girls, used multicomponent strategies, and involved targeting both physical activity and sedentary behavior. CONCLUSIONS Interventions to increase physical activity in adolescent girls show small but significant effects, suggesting that behavior change may be challenging. Results suggest some approaches that appear to be successful.