Study objective: To investigate the magnitude and consistency of the associations between smoking and body mass index (BMI) in different populations.
Design: A cross sectional study.
Setting and participants: About 69,000 men and women aged 35-64 years from 42 populations participating in the first WHO MONICA survey in the early and mid 1980s.
Main results: Compared to never smokers, regular smokers had significantly (p < 0.05) lower median BMI in 20 (men) and 30 (women) out of 42 populations (range -2.9 to 0.5 kg/m2). There was no population in which smokers had a significantly higher BMI than never smokers. Among men, the association between leanness and smoking was less apparent in populations with relatively low proportions of regular smokers and high proportions of ex-smokers. Ex-smokers had significantly higher BMI than never smokers in 10 of the male populations but in women no consistent pattern was observed. Adjustment for socioeconomic status did not affect these results.
Conclusions: Although in most populations the association between smoking and BMI is similar, the magnitude of this association may be affected by the proportions of smokers and ex-smokers in these populations.