title: Relationship between smoking and obesity: a cross-sectional study of 499,504 middle-aged adults in the UK general population.
abstract: BACKGROUND
  There is a general perception that smoking protects against weight gain and this may influence commencement and continuation of smoking, especially among young women.
  
  
  METHODS
  A cross-sectional study was conducted using baseline data from UK Biobank. Logistic regression analyses were used to explore the association between smoking and obesity; defined as body mass index (BMI) >30 kg/m2. Smoking was examined in terms of smoking status, amount smoked, duration of smoking and time since quitting and we adjusted for the potential confounding effects of age, sex, socioeconomic deprivation, physical activity, alcohol consumption, hypertension and diabetes.
  
  
  RESULTS
  The study comprised 499,504 adults aged 31 to 69 years. 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). Former smokers were more likely to be obese than both current smokers (adjusted OR 1.33 95% CI 1.30-1.37) and never smokers (adjusted OR 1.14 95% CI 1.12-1.15). Among smokers, the risk of obesity increased with the amount smoked and former heavy smokers were more likely to be obese than former light smokers (adjusted OR 1.60, 95% 1.56-1.64, p<0.001). Risk of obesity fell with time from quitting. After 30 years, former smokers still had higher risk of obesity than current smokers but the same risk as never smokers.
  
  
  CONCLUSIONS
  Beliefs that smoking protects against obesity may be over-simplistic; especially among younger and heavier smokers. Quitting smoking may be associated with temporary weight gain. Therefore, smoking cessation interventions should include weight management support.
authors.affiliation: Institute of Health and Wellbeing, University of Glasgow, Glasgow, United Kingdom; School of Nursing, College of Health and Allied Sciences, University of Cape Coast, Cape Coast, Ghana.
authors.forename: Shadrach
authors.initials: S
authors.lastname: Dare
authors.affiliation: Institute of Health and Wellbeing, University of Glasgow, Glasgow, United Kingdom.
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Mackay
authors.affiliation: Institute of Health and Wellbeing, University of Glasgow, Glasgow, United Kingdom.
authors.forename: Jill P
authors.initials: JP
authors.lastname: Pell
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology / Q000473:pathology*; D016017:Odds Ratio; D012307:Risk Factors; D012907:Smoking; D011795:Surveys and Questionnaires; D006113:United Kingdom / Q000453:epidemiology