In this systematic review, investigators expand on previous reviews of obesity prevention interventions by including recent studies from all parts of the world. School-based interventions with combined diet and physical activity components and a home element had greatest effectiveness; evidence in support of the effect of preschool-based, community-based, and home-based interventions was limited by a paucity of studies and heterogeneity in study design. The effectiveness of school-based interventions that combined diet and physical activity components suggests that they hold promise for childhood obesity prevention worldwide.