Non-alcoholic fatty liver disease (NAFLD) is not uncommon in non-obese people. We examined the independent predictors of NAFLD in a group of non-obese and non-diabetic men and women in Rasht, Iran. Sixty-one adults aged 38.4 +/- 8.4 years (32 men and 29 women) with body mass index (BMI) <30 kg/m(2) and non-diabetic with clinical features of NAFLD who visited our center between 2007 and 2009 were compared to 147 non-obese, nondiabetic and normal liver subjects (40 men and 107 women) aged 40.8 +/- 9.1. Data on blood lipids, anthropometry, fasting blood glucose, exercise, and educational levels were gathered using a questionnaire. Logistic regression analysis revealed that weight gain during adulthood [OR = 1.90 (95% CI = 1.03-1.84), P < 0.04] and high serum triglyceride levels [OR = 1.19 (95% CI = 1.09-1.28), P < 0.0001] were independent predictors of NAFLD in this group of non-obese subjects. BMI, educational levels, gender, and habitual physical activity were not independently related to NAFLD in this study. These data suggest that weight gain after 20 years of age rather than BMI and high levels of triglyceride may serve as screening tool for NAFLD in clinical practice in this population. In nutritional management of these apparently normal weight subjects with NAFLD modest weight loss is necessary.