Mixed
Current smoking is associated with a lower prevalence of obesity compared to never smoking, but this protective association is not present in individuals aged 40 or younger and is reversed in heavy smokers (>20 cigarettes/day).
If you are a heavy smoker, you may actually have a higher risk of obesity than non-smokers, contradicting the idea that smoking helps you stay thin. If you are under 40, smoking does not appear to protect you from obesity. Quitting smoking often leads to weight gain, so plan for weight management support when you quit.
Overall, current smokers were less likely to be obese than never smokers (adjusted OR 0.83 95% CI 0.81-0.86). However, there was no significant association in the youngest sub-group (≤40 years)... heavy smokers were more likely to be obese than never smokers (adjusted OR 1.09, 95% CI 1.02–1.17, p = 0.01).
Why this rating
Large sample size (n=499,504) and rigorous adjustment for confounders, but cross-sectional design limits causal inference.
Source
Relationship between Smoking and Obesity: A Cross-Sectional Study of 499,504 Middle-Aged Adults in the UK General Population
Shadrach Dare et al. · PLoS ONE · 2015
DOI 10.1371/journal.pone.0123579
Related findings · Mixed
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