The purpose of the study is to evaluate whether the addition of Diamel, a nutritional supplement, to hypocaloric diet and exercise could improve the histological results (steatosis, necro-inflammatory activity and fibrosis), insulin resistance, aminotransferase levels and anthropometric measures in comparison with a placebo-controlled group with hypocaloric diet and exercise during 52 weeks of treatment in patients with nonalcoholic steatohepatitis.

Inclusion Criteria:

• Histological diagnosis of steatohepatitis (minimal histological criteria for steatohepatitis include steatosis involving at least 5% of hepatocytes, lobular inflammation, and/or fibrosis)
• Age between 18 and 70 years
• Ability to provide informed consent
• Absence of significant alcohol ingestion (weekly ethanol consumption of less than 40 g)

Exclusion Criteria:

• Presence of other form of liver diseases (viral or autoimmune hepatitis, drug-induced liver disease, metabolic and hereditary liver disease and α-1 antitrypsin deficiency)
• Pregnancy or lactation
• Decompensated cirrhosis
• Presence of secondary cause of NAFL such as medications that induce steatosis (corticosteroids, estrogens, methotrexate, amiodarone, tamoxifen and calcium channel blockers) and gastrointestinal bypass surgery
• Pharmacological treatment with some potential benefit on NAFL including ursodeoxycholic acid, vitamin E, betaine, pioglitazone, rosiglitazone, metformin, pentoxifylline or gemfibrozil
• Fasting glucose levels greater than 250 mg per deciliter (13.3 mmolm per liter)
• Contraindication to liver biopsy
• Refusal to participate in the study
• Concomitant disease with reduced life expectancy
• Severe psychiatric conditions
• Drug dependence