Using quadratic inference functions to determine the factors associated with obesity: findings from the STEPS Survey in Iran

Abstract Purpose The last study that had a representative sample of the Iranian population and examined the association between sociodemographic and lifestyle factors with obesity used data from the 1999 to 2000 National Health Survey in Iran. Concern about the increased prevalence of obesity has heightened interest in the association between varieties of these factors with obesity among Iranian households. Methods Data (20,917 adults) were taken from the 2009 STEPwise approach to Surveillance survey in Iran that was conducted under the supervision of World Health Organization. Using quadratic inference function, we evaluated the relation of age, sex, physical activity, serving of fruit and vegetable, employment status, smoking, and place of residence with obesity. Results Using 20–30 years as the reference group, the obesity odds ratios (ORs) were 2.48, 3.79, 3.52, and 3.15 for ages 30–40, 40–50, 50–60, and 60+ years, respectively. Obesity OR for female was 2.63, compared with male. Obesity ORs for smokers and ex-smokers were 0.64 and 1.18, respectively, compared with nonsmokers. Among Iranian adult, obesity ORs for the moderate and vigorous physical activity were 0.99 and 0.90, respectively, compared with low level. The estimated odds of obesity were 46% higher for rural adults. Obesity ORs for public and private employed were 0.79 and 0.76, respectively, compared with unemployed. Conclusions Our results may provide better insights of the factors associated with obesity and can be used as a basis to reinforce health programs to prevent obesity in Iran.