Does Smoking Keep You Slim? Evidence from Japan's Smoking Ban in the Workplace

Long-term time-series data show a strong negative correlation between obesity and smoking prevalence, which may not reflect the causality. Many heavy smokers claim that smoking helps them maintain a slim body and keep smoking despite the health risks. Using the Japan Household Panel Survey, this study investigates the causal effect of smoking on body shapes by exogenous variations of Japan's smoking ban in the workplace. Contrary to previous studies, our instrumental variable estimates show that smoking has no effect on body mass index, obesity and underweightness. We also construct an overidentified model to test the robustness of our results.