Researchers investigating the prevalence of childhood obesity have documented an upward trend. However, little research has focused on the processes that might explain changes in children's Body Mass Index (BMI), a commonly used measure to determine overweight and obese status. The purpose of this dissertation is to elucidate the pathways in which child, family, and community characteristics might influence children's BMI. Specifically, using an ecological framework, this study investigates how children's participation in community-based physical activity mediates the influences of child, family, and community characteristics on change in BMI. Data from kindergarten through the fifth-grade from a national longitudinal dataset, the Early Childhood Longitudinal Study - Kindergarten Class of 1998 - 99 (ECLS-K), are utilized to address the research questions.

Results from this study revealed that higher community disorder was associated with lower levels of physical activity participation and with greater parental restriction about the time children spent watching TV. Higher parental education was associated both direct, and indirectly--through feeding practices, with lower levels of BMI at kindergarten and with a subsequent decline in BMI. Higher parental education was also associated with greater parental restriction about the time children spent watching TV and higher levels of physical activity participation. The observed association between trajectories of community-based physical activity participation and trajectories of BMI diminished after controlling for family socioeconomic status. Different familial experiences in relation to factors that predict the risk for developing obesity were also found among different race/ethnic groups. Overall, findings from this study demonstrate family mechanisms through which community disorder influence risk for developing child obesity.