| This dissertation consists of two substudies. The objectives of Substudy 1 were as follows: 1) to examine changes in obesity rates throughout elementary school in a large sample of children with respect to socioecological factors, especially trends in body mass index (BMI) and the prevalence of "severe high obesity" during elementary school, and 2) to explore the longitudinal effect of socioecological obesogenic factors (including individual, parental, familial, and environmental factors) on the transition from a normal/healthy weight to being overweight or obese among children aged three to 13 years old. This longitudinal panel study used the Early Childhood Longitudinal Study Program (ECLS-K). A modified socioecological model was used as a conceptual framework to guide the investigation of this study's research questions. Two longitudinal ordered regressions were performed to determine the associations between socioecological obesogenic variables (e.g., family activity and parental involvement) and changes in obesity rates, as well as the transition from a normal/healthy weight to being overweight, obese, or severely obese. A total of 1,264 children (representing 379,297 at the population level) were identified for this study (mean age: 5.24 years; female: 48.7% at baseline). Hispanics and other nonwhite children, children with less socioeconomic and environmental support, and children living in households with fewer family members were more likely than their counterparts to gain weight (all ps < 0.05). This study revealed multiple dimensions of how sociological obesogenic factors influence children's weight increases and transitions in a longitudinal setting. Unhealthy BMI status among children was affected not only by individual factors but also by parents, family, and environments. Parents and family play a crucial role in children's physical activity and nutrition, and obtaining family and environmental support is critically important for maintaining a healthy BMI status. The findings suggest that a greater focus on family and social support is necessary to help children maintain a healthy weight over time.;Substudy 2 aimed to investigate the association between the Head Start Program and children's BMI status, as well as their quality of life with respect to socioecological obesogenic factors. This cross-sectional study employed the ECLS-K as well. A propensity-score matching analysis was performed to examine the association between the Head Start Program and children's BMI status, as well as the quality of life, controlling for socioecological obesogenic factors. A total of 3,753 children (representing 1,284,209 at the population level) were recruited for this study (mean age: 13.69 years; female: 49.42%). In the final matched model, the Head Start Program did not have a statistically significant effect on children's obesity. Children who were African American, had less participation in school-sponsored activities, perceived themselves as overweight, lived in a household with fewer family members, and had less strict TV regulations were more likely to be overweight than their counterparts (all ps < 0.05). Evidence suggests that multiple dimensions of sociological obesogenic factors---including individual as well as parental, familial, and community support factors---affect the weight of children from low-income families and should be considered when establishing behavioral and policy interventions to thwart the childhood obesity epidemic. |
