Obesity is a global epidemic and children are affected in increasing numbers. Overweight children are at increased risk of becoming overweight adults with associated chronic diseases. In this update, we present key findings from a review of the current literature focused on potential causes and strategies for preventing childhood obesity. We highlight recent evidence regarding the role of genetics, maternal body mass index, postnatal influences, and environmental effects throughout childhood in predicting overweight. We also summarize the results of new research that examined the effectiveness of intervention strategies implemented in a variety of settings: home, school, community, and health care system. Statements recently released by the Centers for Disease Control and Prevention (CDC) and the US Department of Health and Human Services emphasize the need for effective policy and environmental change to promote healthy lifestyle change at the individual and population levels.