Nonalcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) is one of the types of fatty liver which occurs when fat is deposited (steatosis) in the liver due to causes other than excessive alcohol use. Non-alcoholic steatohepatitis (NASH) is the most extreme and fast progressing subtype of NAFLD. NAFLD is the most common liver disorder in developed countries.

NAFLD is related to insulin resistance and the metabolic syndrome; as of 2017 a combination of improved diet and exercise appeared to be the most efficient way to manage NAFLD and reduce insulin resistance. It may respond to treatments originally developed for other insulin-resistant states (e.g. diabetes mellitus type 2) such as metformin, and thiazolidinediones. Up to 80% of obese people have the disease and up to 20% normal-weight people might develop it. It is estimated that 24% of the worldwide population is affected in 2017. While largely unknown in the 2000s, NASH and NAFLD are the leading cause of chronic liver disease as of 2017.

About 12 to 25% of people in the United States have NAFLD, while NASH affects between 2 and 5% of people in the United States. The annual economic burden was estimated at US$103 billion in the USA in 2016.

Official guidelines are provided since 2016 by a few institutions such as the American Association for the Study of Liver Diseases (AASLD) and the United Kingdom's National Institute for Health and Care Excellence (NICE).