The purpose of this article was to identify psychosocial determinants of childhood and adolescent obesity. Some of the determinants were considered non-modifiable such as genetics, sex, age, and race. The risk of developing obesity started early on in life, with high birth weight, rapid growth in infancy, maternal smoking during pregnancy, and lack of breastfeeding indicated as positive predictors. Family food environment and dietary behaviors were considered modifiable determinants and included: consumption of unhealthy foods, portion sizes, snacking, and number of family meals. Physical activity was also considered a protective factor against the development of obesity, with overweight children significantly less active than those who were non-overweight. Recommendations for successful interventions and future research were discussed.