 Community-based programs are needed to improve dissemination of efficacious treatment for adolescent obesity. The current study aims to modify a community-based program, delivered through the YMCA, to increase its effectiveness with adolescents. Adolescents will be randomized to either a 16-week standard program JOIN or a targeted intervention tailored for adolescents TEEN JOIN. Primary outcomes include changes in BMI, objectively measured physical activity, and self-efficacy, assessed at 4 months and 10 months following randomization. 