Fatty liver disease is caused by excess fat in the liver. When fat accumulates, the liver becomes inflamed and damaged. The medical term for this is non-alcoholic fatty liver disease (NAFLD). Excess alcohol use can also cause the liver to become fatty, referred to as alcoholic liver disease (ALD).

NAFLD is quickly becoming the most common liver disease in the United States. Estimates of the prevalence of NAFLD range from 5 to 30 percent of the U.S. population.

Fatty liver is potentially serious. The two basic categories of NAFLD are defined by the degree of liver damage that has occurred. Non-alcoholic fatty liver (NAFL) or non-alcoholic fatty liver disease (NAFLD) are common terms used when there is simply hepatic steatosis and no liver damage. If fat accumulation has caused inflammation or damage to liver cells, the condition is called non-alcoholic steatohepatitis (NASH). Over time, cirrhosis may develop, which can lead to liver cancer or liver failure.

Lifestyle-related factors often play a role in the development of NAFLD and NASH. Obesity is the number one risk factor for NAFLD and NASH. Even a small weight gain, particularly in the waistline, is associated with non-alcoholic fatty liver disease.

Often, there are no symptoms associated with NAFLD, especially in its early stages. Fatigue is a common complaint. In advanced cases of NASH, especially if there is cirrhosis, patients may lose weight and feel weak.

There is no simple test for NAFLD. Often the health care provider will make a diagnosis based on medical history, symptoms, a physical exam and blood tests. 

Regular exercise, losing weight, and eating a low-fat diet can reverse NAFLD. Stopping or reducing alcohol use can also improve liver health. There are no FDA-approved treatments for non-alcoholic fatty liver disease (NAFLD) or its later stage, non-alcoholic steatohepatitis (NASH). There are NASH products in the pipeline.

Editor’s note: This was originally published in 2017 and has been updated.