Two articles that contribute to the literature on psychosocial predictors of youths' physical activity motivation and behavior were chosen for commentary. The first article by Fenner and colleagues showed that a family-based intervention was effective at increasing overweight adolescents' self-determined motivation for physical activity and healthy eating and their quality of life. Significant study contributions include a multidisciplinary team of researchers, multiple pre and post intervention assessments, and a longitudinal test of mechanisms of change. Findings contribute to understanding how to provide overweight adolescents with support and choices at a critical developmental period to ultimately foster lifelong healthy behaviors. The second article by Garn and colleagues examined longitudinal relationships between physical self-perceptions and physical activity among children. Important study contributions include use of accelerometers to assess physical activity and tests of bidirectional relationships. The sample of young children aged 8-11 years also contributes to the literature. Results highlight body acceptance as an important mechanism of focus to foster children's physical activity behavior. Overall, the highlighted studies show that parental support and positive self-perceptions are important to consider in supporting youths' active lifestyles.