Purpose of Review <p>Childhood cancer patients and survivors often suffer from obesity and metabolic syndrome. The purpose of this review is to evaluate the available data on how body composition and metabolism are affected by childhood cancer and its treatment.</p> Recent Findings <p>Though severity varies among cancers and treatments, childhood cancer patients often exhibit acute changes in metabolism and body composition during the induction of therapy. Particularly prevalent is a decrease in lean mass accompanied by excess adiposity, often called sarcopenic obesity. These metabolic burdens can last for decades after therapy and contribute to future morbidity and mortality. A few promising studies show that dietary and physical activity interventions may reduce these outcomes.</p> Summary <p>Body composition and metabolic effects occur during cancer treatment and can increase the risk of chronic disease in survivors. More studies are needed to best plan monitoring and intervention strategies to prevent metabolic syndrome and its sequelae in childhood cancer survivors.</p>