The presence of hepatic steatosis in individuals without a known cause of chronic liver disease, including excessive alcohol consumption, is the hallmark of nonalcoholic fatty liver disease (NAFLD). Although NAFLD is usually associated with obesity, nonobese patients can also present with NAFLD ("lean NAFLD"). Our objective was to determine factors independently associated with lean NAFLD in the United States population. For this purpose, we used data from National Health and Nutrition Examination Survey III (NHANES III) conducted between 1988 and 1994 with available hepatic ultrasound, clinico-demographic, and laboratory data. NAFLD was defined as the presence of moderate-severe hepatic steatosis (by ultrasound), the absence of excessive alcohol use (>20 g/d in men and 10 g/d in women), hepatitis B surface antigen(-), and hepatitis C antibody(-). Nonalcoholic steatohepatitis (NASH) was defined as having moderate-severe steatosis and elevated aminotransferases in the presence of type 2 diabetes or insulin resistance (IR). Logistic regression was used to identify independent predictors of lean NAFLD. As a result, of the 11,613 participants included in the study, 2185 (18.77% ± 0.76%) had NAFLD; of these, 307 (11.78% ± 1.03%) had NASH. Multivariate analysis showed that lean NAFLD was independently associated with younger age, female sex, and a decreased likelihood of having IR and hypercholesterolemia (p values < 0.05). Additionally, multivariate analysis showed that NASH was independently associated with being Hispanic, having a younger age, and having components of metabolic syndrome such as hypertension (p values < 0.05). Therefore, we conclude that lean individuals with NAFLD have a different clinical profile than overweight-obese individuals with NAFLD. Furthermore, patients with NASH are commonly Hispanic and have components of metabolic syndrome.