Childhood obesity is a preventable multi-systemic disease that has become an epidemic. In this narrative review, we showed evidence, in the literature, of the affectation of body systems by obesity. Co-morbid conditions of obesity in the cardiovascular, nervous, dermatological, respiratory, endocrine, reproductive, musculoskeletal, gastrointestinal, and renal systems, and its effects on mental health are discussed. Obesity ultimately reduces the quality of life of children and is a leading cause of preventable deaths. Effective measures aimed at the prevention of obesity and the treatment of its co-morbid conditions should be taken.