Treatment for NAFLD is weight loss by dietary changes and exercise. There is tentative evidence for pioglitazone and vitamin E; bariatric surgery can improve or resolve severe cases. Those with NASH have a 2.6% increased risk of dying per year.

NAFLD is the most common liver disorder worldwide and is present in approximately 25% of the world's population. It is also very common in developed nations, such as the United States, and affected about 75 to 100 million Americans in 2017. Over 90% of obese, 60% of diabetic, and up to 20% normal-weight people develop it. NAFLD is the leading cause of chronic liver diseaseand the second most common reason for liver transplantation in the US and Europe as of 2017.NAFLD affects about 20 to 25% of people in Europe. In the United States, estimates suggest between 30 and 40% of adults have NAFLD, and about 3 to 12% of adults have NASH. The annual economic burden was approximately US$103 billion in the US in 2016.

Definition

An abnormal accumulation of fat in the liver in the absence of secondary causes of fatty liver, such as significant alcohol use, viral hepatitis, or medications that can induce fatty liver characterizes non-alcoholic fatty liver disease (NAFLD). The term NAFLD encompasses a continuum of liver abnormalities, from non-alcoholic fatty liver (NAFL, simple steatosis) to non-alcoholic steatohepatitis (NASH). These diseases begin with fatty accumulation in the liver (hepatic steatosis). A liver can remain fatty without disturbing liver function (NAFL), but by various mechanisms and possible insults to the liver, it may also progress into non-alcoholic steatohepatitis (NASH), a state in which steatosis is combined with inflammation and sometimes fibrosis (steatohepatitis). NASH can then lead to complications such as cirrhosis and hepatocellular carcinoma.

A new name, metabolic dysfunction associated fatty liver disease, was proposed after 70% of a panel of experts expressed support for this name.

Signs and symptoms

Overview of non-alcoholic fatty liver disease
People with NAFLD often have no noticeable symptoms, and NAFLD is often only detected during routine blood tests or unrelated abdominal imaging or liver biopsy. In some cases, NAFLD can cause symptoms related to liver dysfunction such as fatigue, malaise, and dull right-upper-quadrant abdominal discomfort. Mild yellow discoloration of the skin may occur, although this is rare. NASH can severely impair liver function, leading to cirrhosis, liver failure, and liver cancer.

Comorbidities

NAFLD is strongly associated with or caused by type 2 diabetes, insulin resistance, and metabolic syndrome (defined as at least three of the five following medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein). It is also associated with hormonal disorders (panhypopituitarism, hypothyroidism, hypogonadism, polycystic ovary syndrome), persistently elevated transaminases, increasing age and hypoxia caused by obstructive sleep apnea, with some of these conditions predicting disease progression.

The majority of normal-weight people affected by NAFLD ("lean NAFLD") have impaired insulin sensitivity, are sedentary, and have increased cardiovascular disease risk and increased liver lipid levels. These are the consequences of a decreased capacity for storing fat and reduced mitochondrial function in adipose tissue and increased hepatic de novo lipogenesis.

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