Public health actions in response to new threats are often taken despite uncertainty about the efficacy of the action. The challenge, then, is to make ongoing judgments about whether actions are taken too soon, before a sufficient understanding of the efficacy of interventions is known, or too late, after much of the prevention potential is lost. The ongoing obesity epidemic presents exactly this type of challenge. General lessons learned from the AIDS and tobacco epidemics as well as others can be useful now as we contemplate options for reversing the ongoing epidemic of obesity in the United States. In this article we briefly review current evidence regarding the efficacy of obesity interventions in both clinical and community settings. We conclude that although little direct evidence is available on the efficacy of interventions for the obesity epidemic, there are some reasonable options derived from experience with other public health epidemics that can contribute to the solution of the obesity problem. J. Nutr. 137: 488-492, 2007.