Nonalcoholic steatohepatitis (NASH) is an underdiagnosed liver disease characterised by steatosis, necroinflammation and fibrosis. This disease may eventually develop into cirrhosis and hepatocellular carcinoma. NASH is highly prevalent among obese individuals and among patients with diabetes mellitus type 2. Nonalcoholic fatty liver (NAFL), a precursor of NASH, is the main cause of elevated serum liver enzymes among the general population. Insulin resistance is a major aetiological factor in NASH. Gradual weight loss, physical exercise and drugs that improve insulin sensitivity are potential therapies.