Smoking cessation and subsequent weight change.

Introduction: People who quit smoking tend to gain more weight over time than those who continue to smoke. Previous research using clinical samples of smokers suggests that quitters typically experience a weight gain of approximately 5 kg in the year following smoking cessation, but these studies may overestimate the extent of weight gain in the general population. The existing population-based research in this area has some methodological limitations.

Methods: We assessed a cohort of individuals born in Dunedin, New Zealand, between 1972-1973 at regular intervals from age 15 to 38. We used multiple linear regression analysis to investigate the association between smoking cessation at ages 21 years to 38 years and subsequent change in body mass index (BMI) and weight, controlling for baseline BMI, socioeconomic status, physical activity, alcohol use, and parity (women).

Results: Smoking status and outcome data were available at baseline and at follow-up for 914 study members. People who smoked at age 21 and who had quit by age 38 had a BMI on average 1.5 kg/m(2) greater than those who continued to smoke at age 38. This equated to a weight gain of approximately 5.7 kg in men and 5.1 kg in women above that of continuing smokers. However, the weight gain between age 21 and 38 among quitters was not significantly different to that of never-smokers.

Conclusions: The amount of long-term weight gained after quitting smoking is likely to be lower than previous estimates based on research with clinical samples. On average, quitters do not experience greater weight gain than never-smokers.