Thesis (Ph.D.) - Indiana University, School of Public Health/University Graduate School, 2019This dissertation project investigated the association between physical activity (PA) and intention to engage in physical activity among children and adolescents, as well as possible correlates of obesity among high school students in Hong Kong. Two studies were conducted. Study 1 evaluated the association between PA and intention to engage in PA among children and adolescents, and the moderation effects of geographical region of study between PA and Reasoned Action Approach (RAA, Fishbein & Ajzen, 2010) -based variables. A total of 36 articles met the inclusion criteria and were meta-analyzed. Intention significantly correlated with and had a medium effect on PA in children. The RAA model displayed a good fit in path analysis. Moderator analyses showed that subjective norms and perceived behavioral control / self-efficacy had a larger effect on children in the rest of the world, compared to their North American counterparts. Study 2 examined potential individual-level and district-level correlates of obesity among high school students in Hong Kong. Data were obtained from the Hong Kong Community Fitness Survey conducted in 2010-2011. Age, sex, cardiovascular fitness, and district nitrogen dioxide concentration were the significant predictors in the final multilevel model. Compared to self-reported moderate to vigorous PA, cardiovascular fitness was found to be a better predictor of adolescents’ body composition. The results provide a summary of current scientific findings about the association between RAA-based variables and PA in children and adolescents, and support RAA as a feasible conceptual framework to study psychosocial factors that underpin PA. Possible areas for future research are discussed.