Associations between body mass index and smoking behaviour: A cross-sectional study of the German adult population.

Background: Both smoking and high body weight are risk factors for disease, hence, the association between smoking and body weight is an important health issue. Furthermore, concern about weight gain after quitting smoking is for many smokers a barrier to smoking cessation. The present study aims to explore the association between body mass index (BMI) and current tobacco smoking status in the population of Germany, and smoking and quitting behaviour amongst smokers (and recent ex-smokers =<12 months since quitting).

Methods: Cross-sectional analysis of two waves of data collected from March through June 2021 through a representative face-to-face household survey in Germany (N = 3 997 respondents aged ≥18). The associations between smoking and quitting behaviours and BMI were analysed through four regression models adjusted for socio-demographic, socio-economic, and smoking characteristics of respondents.

Results: Long-term ex-smokers (>= 12 months since quitting smoking) were more likely to have a higher BMI compared to never smokers (β = 0.64, 95% confidence interval (CI) = 0.10-1.19). There was no statistically significant association between current smoking status or recent ex-smoking status and BMI (β = -0.29,95 %CI = -0.75-0.17 and β = -0.53, 95 %CI = -2.45-1.40). Among current smokers, no statistically significant association was found between BMI and the motivation to stop smoking (OR = 1.01, 95 %CI = 0.99-1.03). Neither number of cigarettes smoked a day nor outcome of most recent quit attempt were related to BMI (β = 0.01, 95 %CI = -0.04-0.05 and OR = 0.41, 95 %CI = 0.05-3.05).

Conclusion: In the German population long-term ex-smoking but not current and recent ex-smoking was associated with increased BMI. Future research should further explore the association between smoking behaviour and abdominal obesity, preferably using a more accurate measure for abdominal obesity than BMI.