Obesity has become a major public health problem in the United States, with a marked upward trend occurring over the past three decades. It plays a critical role in the development of cardiovascular risk factors that mediate the evolution of asymptomatic cardiovascular disease. Longitudinal observations of children, adolescents, and young adults enrolled in the Bogalusa Heart Study show that obesity persists over time and is linked to the clustering of components of metabolic syndrome including hyperinsulinemia/insulin resistance, dyslipidemia, and hypertension, thereby creating a long-term burden of cardiovascular risk beginning in childhood. This burden is associated with subclinical and adverse structural and functional changes of the cardiovascular system in youth. Ultimately, these changes can result in morbidity from disease, as exemplified in the Framingham Heart Study. Obesity is governed by the interplay of both genetic and environmental factors. Unlike genetic factors, lifestyle behaviors are amenable to modification. Since obesity is so widespread and underlying cardiovascular disease is so prevalent, health education beginning in childhood is suggested as an approach to prevention.