A related editorial discusses this study, as well as other research that have shown that early adulthood is not only a period of risk for the development of obesity, but also a period of risk for excessive weight gain. Efforts to prevent obesity have focused on children and adolescents. However, the 2-fold difference in the prevalence of obesity between the ages of 6-11 years (17%) and 20-39 years (34%), rates of excessive weight gain in young adults, and the increased morbidity and mortality associated with excessive weight gain indicate that efforts to prevent and control obesity in young adults should be accorded a high priority. The challenge will be that many individuals, particularly men between the ages of 20 and 39 years feel healthy, and have no medical problems that precipitate a visit to a physician. The prevalence of obesity emphasizes that it will not be possible to provide effective treatment for all of those affected. Therefore, efforts to prevent and control this widespread disease must be renewed.