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Because efforts to lose weight pose tremendous challenges, primary prevention of weight gain is a global priority. Since weight stability requires a balance between calories consumed and calories expended, the advice to “eat less and exercise more” would seem to be straightforward. However, weight gain often occurs gradually over decades (about 1 lb per year), making it difficult for most people to perceive the specific causes. Weight-loss trials have typically enrolled obese or overweight persons who attempted substantial short-term weight loss on specialized diets, thus limiting the generalizability of the findings to nonobese populations and to the factors that determine long-term, gradual weight gain.
Several lifestyle behaviors may influence whether or not a person can maintain energy balance over the long term. For instance, the consumption of sugar-sweetened beverages, sweets, and processed foods may make it harder to do so, whereas the consumption of whole grains, fruits, and vegetables might make it easier. Physical activity should also influence long-term weight gain, but evidence to support this expectation has been surprisingly inconsistent. In addition, the duration of television viewing and of sleep may influence energy consumption, energy expenditure, or both. Different lifestyle behaviors have often been evaluated separately, thus limiting relative comparisons or the quantification of combined effects. In addition, most studies of long-term weight gain have evaluated current behaviors, but changes in behavior over time may be more relevant in terms of both their biologic effects on long-term weight gain and their translation into prevention strategies. We investigated the relationship between multiple lifestyle changes, both independently and jointly, and long-term weight gain in nonobese women and men participating in three separate, prospective studies.