Background: Smokers usually have a lower Body Mass Index (BMI) when compared to non-smokers. Such a relationship, however, has not been fully studied in obese and morbidly obese patients. The objective of this study was to evaluate the relationship between smoking and BMI among obese and morbidly obese subjects.
Methods: In a case-control study design, 1022 individuals of both genders, 18-65 years of age, were recruited and grouped according to their smoking status (smokers, ex-smokers, and non-smokers) and nutritional state according to BMI (normal weight, overweight, obese, and morbidly obese).
Results: No significant differences were detected in the four BMI groups with respect to smoking status. However, there was a trend towards a higher frequency of smokers among the overweight, obese, and morbidly obese subjects compared to normal weight individuals (p = 0.078). In a logistic regression, after adjusting for potential confounders, morbidly obese subjects had an adjusted OR of 2.25 (95% CI, 1.52-3.34; p < 0.001) to be a smoker when compared to normal weight individuals.
Discussion: In this sample, while the frequency of smokers diminished in normal weight subjects as the BMI increased, such a trend was reversed in overweight, obese, and morbidly obese patients. In the latter group, the prevalence of smokers was significantly higher compared to the other groups. A patient with morbid obesity had a 2-fold increased risk of becoming a smoker. We speculate that these finding could be a consequence of various overlapping risk behaviors because these patients also are generally less physically active and prefer a less healthy diet, in addition to having a greater alcohol intake in relation to their counterparts. The external validity of these findings must be confirmed.