Endocrine Abstracts

Objective: To explore the relationship between body mass index (BMI) and smoking in a cross-sectional and longitudinal study.

Methods: In the 4th and 5th Tromsø studies in 1994 and 2001, 27158 and 8130 subjects participated. Height and weight were measured and a questionnaire on life style factors filled in.

Results: Complete datasets were available for 10920 men and 12092 women in the 4th Tromsø study. Among these subjects, 2364 men and 2738 women also participated in the 5th Tromsø study. In the 4th Tromsø study, smokers as a group had lower BMI (mean±S.D.) compared to non-smokers (25.0±3.4 vs 25.9±3.3 kg/m², P<0.001). However, among smokers there was an increase in BMI with increasing number of cigarettes smoked, particularly in males, where those smoking 1–5 cigarettes daily had BMI 24.9±3.3 vs 25.9±3.3 kg/m² in those smoking ≥21 cigarettes daily. The increase in BMI with number of cigarettes was paralleled by an increase in coffee and alcohol consumption. In the longitudinal study, all smoking subgroups increased in BMI from 1994 to 2001. The smallest increase was among those who started smoking during this period, whereas the highest increase was among those who quitted smoking. For those that stopped smoking between 1994 and 2001, the increase in BMI was positively related to the number of cigarettes smoked in 1994. Changes in coffee consumption occurred in parallel with changes in smoking habits.

Conclusion: There is a U-shaped relationship between smoking and BMI. Heavy smoking is associated with an unhealthy lifestyle, which appears to override the weight reducing effect of cigarette smoking.