The prevalence of childhood obesity continues to increase worldwide. Its presence is associated with significant adverse effects on health including an increased propensity to type II diabetes, cardiovascular, respiratory, and liver disease. In the vast majority of children, obesity is lifestyle-related, yet there is a dearth of evidence on how to best develop effective prevention and treatment strategies. This review outlines the importance of childhood and adolescent growth on long-term health, the definitions used to define obesity in children (along with up-to-date prevalence data), causes and consequences, and aspects of prevention and management.