The percentage of failure and relapse in the treatment of obesity is high. Where possible, the preferred strategy for preventing obesity is to modify eating habits and lifestyles. This article aims to provide a framework for evidence on the most effective interventions for addressing childhood obesity, both from a prevention point of view, as well as reducing it, when it is already established. After a review of the scientific literature, the issues that must be considered both in the universal and selective prevention of childhood obesity are presented. Also, in light of the controversy over the tools for measuring and controlling the problem, some clarification is provided on the criteria. Finally, the approach to the prevention of overweight and obesity with a community perspective is separated, with two short protocols being offered with diagrams of the basic procedure to follow.