Nonalcoholic Fatty Liver: The Association with Metabolic Abnormalities, Body Mass Index and Central Obesity-A Population-Based Study

Background: To assess the prevalence of nonalcoholic fatty liver (NAFL) in Iran and to evaluate correlates of NAFL in categories of body mass index (BMI). Methods: Using a cluster random sampling approach, 7723 subjects over 18 years of age underwent abdominal ultrasonography, laboratory evaluations, blood pressure, and anthropometric measurements and were interviewed to obtain baseline characteristics. Prevalence of NAFL according to BMI and waist to hip ratio and its association with metabolic abnormalities in categories of BMI were assessed in multivariate analysis. Results: The overall prevalence of NAFL was 35.2% [95% confidence interval (CI) 34.1-36.3]. A significant number of subjects with BMI <30 had NAFL [22.1% (CI 21.0-23.2)]. Waist to hip ratio for 38.2% (CI 35.6-40.8) of the subjects with NAFL, and BMI <30 was higher than normal values. The odds ratio for association of NAFL and dyslipidemias were higher in subjects with BMI <30 versus those with BMI 30: (1) hypertriglyceridemia: 2.21 vs. 1.57, P=0.006; (2) lower high-density lipoprotein: 1.29 versus 0.98, P=0.046. Higher low-density lipoprotein also revealed greater association with NAFL in subjects with BMI <25 than those with BMI 25 (odds ratio 1.84 vs. 1.1, P=0.015). Conclusions: NAFL shows stronger association with central obesity compared to high BMI. NAFL has stronger association with dyslipidemias in subjects with low compared with high BMI.