Non Alcoholic Fatty Liver Disease and conditions caused by Obesity

In the UK and other developed countries, the most common cause of liver dysfunction is now fat induced liver cell damage. This form of liver disease is called Non Alcoholic Fatty Liver Disease (NAFLD) to distinguish it from alcohol induced liver disease to which it is microscopically similar. The course of NAFLD is determined by whether there is fat alone (steatosis) or fat plus inflammation in the liver. This latter stage is called Non Alcoholic Steatohepatitis (NASH). NAFLD and NASH are now more common than chronic hepatitis B, C or other causes of liver disease.

NAFLD is caused by obesity induced increases in circulating insulin levels. This state of increased insulin levels causes fat deposition in the liver. The fat itself damages the liver cells and the resulting inflammation, leads to activation of scar forming cells in the liver. The scar forming process is called fibrosis. Over-exuberant deposition of scar tissue i.e. fibrosis, is known as cirrhosis. Cirrhosis is a stage of liver disease where the normal and neat architecture of the liver is destroyed and liver function may be disturbed. Not all patients with fat induced liver disease will develop cirrhosis: only a proportion will after some years. We do not at present know the factors that govern why some patients progress and others do not. This is an active area of research. It is important therefore to appreciate that NAFLD is not a benign disease. It may progress.

The consequences of progression are cirrhosis and perhaps a requirement for liver transplantation. It has been estimated that at the present rate of growth in the number of patients with NAFLD, this disease will become the commonest cause of liver transplantation in developed countries by 2020. Recently it has been confirmed that NAFLD also causes primary liver cancer (hepatocellular carcinoma, HCC). Primary liver cancer is cancer of the liver that originates within the liver and is not due to spread from another organ. The incidence of primary liver cancer is rising worldwide and is thought due NAFLD.

Given the consequences of NAFLD, an awareness of its links with obesity is vital to ensure that obese patients are appropriately screened and managed for liver disease.

Definition

Fatty Liver (Hepatosteatosis)