Non-alcoholic fatty liver disease (NAFLD) is a condition caused by hepatic steatosis, meaning excess fat in the liver. When fat accumulates, the liver becomes inflamed and damaged. Excess alcohol use can also cause the liver to become fatty, a condition known as alcoholic liver disease. NAFLD occurs when the origin of the fatty liver is unrelated to alcohol.

The two basic categories of NAFLD are defined by the degree of liver damage that has occurred. Non-alcoholic fatty liver (NAFL) is the term 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.

Non-alcoholic fatty liver disease 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. Veronica Setiawan and colleagues analyzed Medicare claims between 1999 and 2012 and reported that more than half of all cases of chronic liver disease were NAFLD-related (Hepatology, December 2016). According to Setiawan, NAFLD affects all races and ethnicities and was the most common cause of cirrhosis among Japanese Americans, Native Hawaiians and Latinos.

Last Reviewed: March 5, 2018