Relationship Between Smoking Behaviors and BMI, Waist Circumference, Adiposity

An overweight man measuring his waist
An overweight man measuring his waist
Body mass index and body fat distribution may influence smoking behaviors.

Higher levels of general and abdominal obesity may increase the risk for an individual taking up cigarette smoking and influence smoking intensity, according to findings from a new study published in The BMJ.

An inverse association between current cigarette smoking and body weight has been demonstrated in observational studies. In addition, cessation of smoking may also be followed by weight gain. Genetic evidence suggests that there may be a possible common biological basis for nicotine addiction and obesity.

In this study, investigators evaluated the hypothesis that obesity causally influences the risk for being a smoker and also of smoking intensity and conducted a Mendelian randomization framework study based on 372,791 individuals from the UK Biobank cohort and independent data from 74,035 individuals from the Tobacco and Genetics (TAG) consortium.

They found that each standard deviation increase in measured body mass index (BMI) was associated with a lower risk for being a current smoker (odds ratio [OR] 0.95; 95% CI, 0.94-0.96) vs being a never smoker. Each standard deviation increase was also associated with a greater risk for being an ever (current and former) smoker (OR 1.12; 95% CI, 1.11-1.13), and a higher BMI, body fat percentage, and waist circumference were associated with an increased risk for being a former smoker vs a current smoker (all P <.001). Each standard deviation increase was also associated with smoking intensity in current smokers (0.65 extra cigarettes smoked per day; 95% CI, 0.56-0.75) and in ever smokers (1.74 extra cigarettes; 95% CI, 1.68-1.79), and a higher BMI was associated with smoking initiation at younger ages.

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“These results highlight the role of obesity in influencing smoking initiation and cessation, which could have implications for public health interventions aiming to reduce the prevalence of these important risk factors,” wrote the investigators.


Carreras-Torres R, Johansson M, Haycock PC, et al. Role of obesity in smoking behaviour: Mendelian randomisation study in UK Biobank.  BMJ. 2018; 361:k1767.