Smoking and its effects on body weight and the systems of caloric regulation.

Cigarette smoking and excess body weight, each of which contributes to poor health and risk of death, appear themselves to be inversely related. Data indicate that smokers weigh less than nonsmokers and that weight gain occurs after the cessation of smoking. The popular wisdom is that this is due to differences in caloric intake: smokers weigh less because they consume less and they gain weight upon stopping smoking as a consequence of consuming more. Cross-sectional data on this point are conflicting, however, with some studies of daily caloric intake suggesting that smokers may, in fact, consume more calories per day than nonsmokers. In addition to affecting ingestive behavior, however, cigarette smoking has a variety of physiological effects that may play a more important role than amount of calories consumed per se in accounting for lower body weights among smokers and weight gain after cessation. Evidence regarding the effects of cigarette smoking and nicotine upon the behavioral, sensory and metabolic components of the processes of caloric regulation and nutrition is reviewed in order to suggest mechanisms by which smoking may affect weight. Longitudinal within-subject designs investigating changes associated with the cessation and initiation of smoking are recommended.