Smoking status and body mass index: A longitudinal study

Introduction: The general consensus is that smoking cessation leads to some degree of weight gain, although considerable disagreement remains regarding the magnitude and duration of this gain. Methods: We investigated the relationship between smoking status and change in body mass index (BMI) over time in a cohort of male participants recruited for a study of cardiovascular risk factors and assessed at multiple timepoints. We further investigated whether calorie consumption, recorded using food frequency questionnaires, mediated any effect of smoking cessation on change in BMI. Results: Our results indicate that never-smokers and ex-smokers differ in BMI from current smokers by an average of 1.6 kg/m², based on a comparison at baseline. Moreover, smoking cessation between timepoints is associated with a corresponding average increase in BMI of 1.6 kg/m². Discussion: These results suggest that when cigarette smokers achieve long-term abstinence, they revert to a mean BMI roughly equivalent to that of never-smokers. Perhaps surprisingly, this difference in BMI was not substantially attenuated following adjustment for calorie and alcohol consumption, suggesting that the effects of smoking cessation on BMI are not mediated entirely by changes in dietary or alcohol consumption behavior.