Childhood obesity is a major national and worldwide public health crisis. The occurrence of childhood obesity, caused to large extent by an imbalance between caloric intake and caloric expenditure, has increased in the last 30 years. Although the prevalence of obesity has stabilized in recent years, it remains a top public health concern in the United States, especially in urban centers. The purpose of this study was to examine the associations between diet, physical activity, and the built environment in relation to the mean body mass index (BMI) of adolescents aged 12 to 17 years living in South Los Angeles, California. The research design, methods, and data analysis were based on the California Health Interview Survey 2007-2013 dataset. This database was mined for the independent variables: physical security, food insecurity, parental education and income, and availability of recreational facilities necessary for a healthy lifestyle; the dependent variable was BMI. Descriptive statistics and multiple regression analysis were used in analyzing for the association between the dependent variable and the independent variables. The outcomes of this study showed no associations between neighborhood physical security, recreational facilities, adolescent's physical activity, parents' education level, parents' income level, and BMI. However, the results did show a significant correlation between adolescent's dietary intake, food security, and BMI. This study will contribute to positive social change by informing public health officials and policy makers of the benefits of food security to healthier eating habits and BMI among the adolescents studied. Resulting actions could result in collaborative efforts toward reduction and prevention of childhood obesity.