Non‐alcoholic fatty liver disease: what is it, when does it occur, and why does it matter?

The rising pandemic of obesity and type 2 diabetes, both manifestations of insulin resistance, has heralded a rise in associated liver injury in the form of non‐alcoholic fatty liver disease (NAFLD). It is estimated that 20–30% of the population in developed countries have NAFLD. NAFLD should be suspected in those with simple clinical signs and biochemistry consistent with insulin resistance. The importance of NAFLD is two‐fold. Firstly, a small number of individuals with NAFLD, itself a relatively benign condition, will progress to more severe stages of liver disease— namely, non‐alcoholic steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma. Secondly, the presence of NAFLD is associated with treatable features of insulin resistance and an elevated risk for type 2 diabetes. Apart from histology, there is currently no effective method to distinguish between NASH and simple steatosis. Identification of a non‐invasive marker to achieve this is much sought after. Pilot studies of lifestyle advice, insulin sensitisers and other medications have shown evidence of improvement in liver histology and serum ALT. However, the cost:benefit ratio of any new therapies, and any potential harms, must be examined carefully before being clinically advocated. Copyright © 2007 John Wiley & Sons.