The obesity epidemic in the United States calls for action on a national level, yet the potential economic effects of such interventions are unclear. Researchers identified six randomized, controlled trials of community-based interventions to address childhood obesity at different ages that demonstrated a significant change in the prevalence of obesity in the target population. The effects obtained in those trials were applied to a new model of obesity through the life course (ages 3-65 years) in order to estimate the health and economic effects from such interventions scaled to the national level. Even the most effective intervention did not persistently affect the national prevalence of obesity more than 20 years after the intervention was completed. Furthermore, the economic impact of interventions was less than 10 percent of the total excess costs related to obesity for each birth cohort. This study underscores the challenges of addressing obesity at the national level and emphasizes how critical it will be to obtain long-term followup data on children enrolled in prior and future trials.