The prevalence rate of childhood obesity has increased rapidly worldwide and has caused great concern globally. The unhealthy weight in children is associated with many adverse health consequences as well as a financial burden for a nation's economy. Despite the substantial amount of childhood obesity prevention research that has been implemented, the number of obese children remains high. Therefore, the purposes of this book are to conduct a meta-analysis to 1) identify the most effective childhood obesity prevention programs through effect size comparison, and 2) identify important program components that affect the effectiveness of the intervention through subgroup analysis.