Assessment of Lean Patients with Non-alcoholic Fatty Liver Disease in a Middle Income Country; Prevalence and Its Association with Metabolic Disorders: A Cross-sectional Study

Background: Recent data has proven that the WHO (world health organization) cut-off for obesity is not applicable to the Asian population. This study aims to estimate the prevalence of lean NAFLD (non-alcoholic fatty liver disease) in the capital of Iran and extract probable predictors for this growing heath issue in this population. Methods: This is a population-based cross-sectional study on apparently healthy subjects over 18 years of age. The participants were interviewed for baseline demographic and clinical information. They were subsequently referred for physical examination and blood sampling. NAFLD was diagnosed using abdominal ultrasonography by a single expert radiologist. Results: Of 927 eligible participants who entered the study, 314 were lean; BMI (body mass index) <25 kg/m(2). The prevalence of NAFLD was 17.52% (95% Exact CI: 13.48%-22.18%). BMI, SBP (systolic blood pressure), DBP (diastolic blood pressure), total cholesterol, HDL (high-density lipoprotein), LDL (low-density lipoprotein) and triglyceride were significantly different in patients with NAFLD. In the final multiple analysis, higher levels of triglyceride, upper SBP and higher BMI even in the range of less than 25 kg/m2 were independent predictors of NAFLD in lean participants. In lean participants with more components of metabolic syndrome, the prevalence of NAFLD increased significantly (all P < 0.01). BMI cut-offs in men and women along with waist circumference cut-off in men could significantly predict the presence of NAFLD in lean patients. After comparing these values, McNemar test showed that BMI cut-offs are more robust than waist circumference cut-offs for predicting the presence of NAFLD in lean subjects (P < 0.01). Conclusion: The prevalence of NAFLD in lean subjects in a sample of Iranian population is 17.52%. Hypertriglyceridemia, higher SBP, and higher BMI especially over 23.2 are independent factors associated with the presence of NAFLD in lean subjects.