Physical activity in the prevention of obesity: current evidence and research issues.

PURPOSE The relation between habitual physical activity and the prevention of overweight and obesity in adults based on the evidence from the epidemiologic literature is described. METHODS Literature was reviewed of current findings from large population-based studies of forward directionality in which physical activity was considered as a primary study factor. RESULTS The longitudinal evidence suggests that habitual physical activity plays more of a role in attenuating age-related weight gain, rather than in promoting weight loss. Moreover, recent data suggest that increasing amounts of physical activity may be necessary to effectively maintain a constant body weight with increasing age. CONCLUSION Over decades, small savings in excess weight gain accumulate into net savings that may be quite meaningful with regard to minimizing the risk associated with obesity-related disorders. The question remains as to how important maintaining a constant body weight through middle age and into older age is to healthy, already-active people of normal body weight.