To assess the national prevalence of overweight and obesity, as well as some associated lifestyle behaviours, for the first time in Iran.

This population-based study was performed in early 2005 as part of the World Health Organization (WHO) STEPwise approach to non-communicable diseases’ risk factor surveillance. Dietary and physical activity habits were assessed by WHO questionnaires.

The study population comprised 89 532 subjects aged over 15 years living in the 28 provinces of Iran.

Overall, 50.4% (n = 45 113) of the participants were male and 64.6% (n = 57 866) were from the urban areas. The national estimates of overweight, obesity and morbid obesity were 28.6%, 10.8% and 3.4%, respectively. Body mass index (BMI) ≥ 25 kg m−2 in men, women, urban residents and rural residents were found in 37%, 48%, 46.7% and 35.5%, respectively. Abdominal obesity was present in 43.4% of women, 9.7% of men, 28.5% of the urban residents and 23% of the rural residents. Overweight as well as generalised and abdominal obesity were more prevalent in the 45–64-year age group. Although there was no significant difference in frequency of consumption of the food groups in subjects with different BMI categories, various kinds of physical activities showed a steady decline with increasing BMI.

The findings of the present study provide alarming evidence for health professionals and policy makers about the very high prevalence of generalised and abdominal obesity in Iran. The unhealthy lifestyle habits, notably sedentary lifestyles in our community, are the major contributing factors for this emerging public health problem.