The Effect of Smoking on Obesity : Evidence from a Randomized Trial

This paper aims to identify the causal effect of smoking on body weight using data from the Lung Health Study, a randomized trial of smoking cessation treatments. We find evidence that quitting smoking leads to an average long-run weight gain of around 11-12 pounds, and that the drop in smoking in recent decades explains 14% of the concurrent rise in obesity. Semi-parametric models provide evidence of a diminishing marginal effect of smoking on weight, while subsample regressions show that the impact is largest for younger individuals, females, those with no college degree, and those with healthy baseline weights