Childhood obesity has become an epidemic on a worldwide scale. This article gives an overview of the progress made in childhood and adolescent obesity research in the last decade, with a particular emphasis on the transdisciplinary and complex nature of the problem. The following topics are addressed: (1) current definitions of childhood and adolescent overweight and obesity; (2) demography of childhood and adolescent obesity both in the United States and globally; (3) current topics in the physiology of fat and obesity; (4) psychosocial correlates of childhood and adolescent overweight and obesity; (5) the three major obesity-related behaviors, that is, dietary intake, physical activity, and sleep; (6) genetic components of childhood and adolescent obesity; (7) environmental influences on childhood and adolescent obesity; and (8) progress in interventions to prevent and treat childhood and adolescent obesity. The article concludes with recommendations for future research, including the need for large-scale, high-dose, and long-term interventions that take into account the complex nature of the problem.