Weight cycling. National Task Force on the Prevention and Treatment of Obesity.

OBJECTIVE: To address concerns about the effects of weight cycling and to provide guidance on the risk-to-benefit ratio of attempts at weight loss, given current scientific knowledge. DATA SOURCES: Original reports obtained through MEDLINE and psychological abstracts searches for 1966 through 1994 on weight cycling, "yo-yo dieting," and weight fluctuation, supplemented by a manual search of bibliographies. STUDY SELECTION: English-language articles that evaluated the effects of weight change or weight cycling on humans or animals. DATA EXTRACTION: Studies were reviewed by experts in the fields of nutrition, obesity, and epidemiology to evaluate study design and the validity of the authors' conclusions based on published data. DATA SYNTHESIS: The majority of studies do not support an adverse effect of weight cycling on metabolism. Many observational studies have shown an association between variation in body weight and increased morbidity and mortality. However, most of these studies did not examine intentional vs unintentional weight loss, nor were they designed to determine the effects of weight cycling in obese, as opposed to normal-weight, individuals.
CONCLUSIONS: The currently available evidence is not sufficiently compelling to override the potential benefits of moderate weight loss in significantly obese patients. Therefore, obese individuals should not allow concerns about hazards of weight cycling to deter them from efforts to control their body weight. Although conclusive data regarding long-term health effects of weight cycling are lacking, nonobese individuals should attempt to maintain a stable weight. Obese individuals who undertake weight loss efforts should be ready to commit to lifelong changes in their behavioral patterns, diet, and physical activity.