Aims
To estimate the prevalence and trends of diabetes mellitus (DM) and impaired fasting glucose (IFG), 2005–2011, and to determine the contribution of obesity to DM prevalence.

Patients and methods
Data from Surveillance of Risk Factors of Non-communicable Diseases (SuRFNCD) conducted in 2005, 2007, and 2011 were gathered. DM was defined as presence of self-reported previous diagnosis or a fasting plasma glucose (FPG) = 7 mmol/L. IFG was diagnosed with FPG levels between 5.6 and 6.9 mmol/L. Prevalence rates for 2011 and trends for 2005–2011 were determined by extrapolating survey results to Iran's adult population. Population attributable fraction (PAF) of obesity was also calculated.

Results
In 2011, IFG and total DM prevalence rates were 14.60% (95%CI: 12.41–16.78) and 11.37% (95%CI: 9.86–12.89) among 25–70 years, respectively. DM was more common in older age (p < 0.0001), in women (p = 0.0216), and in urban-dwellers (p = 0.0001).

In 2005–2011, trend analysis revealed a 35.1% increase in DM prevalence (OR: 1.04, 95%CI: 1.01–1.07, p = 0.011); albeit, IFG prevalence remained relatively unchanged (OR: 0.98, 95%CI: 0.95–1.00, p = 0.167). In this period, DM awareness improved; undiagnosed DM prevalence decreased from 45.7% to 24.7% (p < 0.001). PAF analysis demonstrated that 33.78%, 10.25%, and 30.56% of the prevalent DM can be attributed to overweight (BMI = 25 kg/m2), general obesity (BMI = 30 kg/m2), and central obesity (waist circumference = 90 cm), respectively. Additionally, the DM increase rate in 2005–2011, was 20 times higher in morbidly obese compared with lean individuals.

Conclusion
More than four million Iranian adults have DM which has increased by 35% over the past seven years, owing in large part, to expanding obesity epidemic.