Among lean patients, fasting glucose, INR, and use of thyroid hormone replacement therapy were independent predictors of NASH in a multivariate model. Lean NAFLD patients were characterized by a severe histological picture similar to obese patients but are more progressed compared to overweight patients. Fasting glucose, INR, and the use of thyroid hormone replacement may serve as indicators for NASH in lean patients. The gene discussed is TG; the disease is metabolic dysfunction-associated steatohepatitis.