Pediatric obesity is a complex disease, with multiple environmental and medical causes and psychological triggers, that results in significant comorbidities. As of 2012, pediatric overweight and obesity affect more than 30% of Americans younger than the age of 21 years. Weight status is determined by calculating body mass index (BMI), which is calculated by dividing weight in kilograms (kg) by height in meters squared (m2). Overweight and obesity are defined by BMI in adults; in pediatrics, they are defined by BMI percentiles as defined by growth charts published by the Centers for Disease Control and Prevention (see Table 1). This entry reviews the epidemiology, etiologies, associated conditions, and management of pediatric obesity.