Symptoms & Causes of NAFLD & NASH

What are the symptoms of NAFLD?

Usually, nonalcoholic fatty liver disease (NAFLD)—including nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH)—is a silent disease with few or no symptoms. You may not have symptoms even if you develop cirrhosis due to NASH.

If you do have symptoms, you may feel tired or have discomfort in the upper right side of your abdomen.

What causes NAFLD?

Experts are still studying the causes of NAFLD. Research suggests that certain health conditions or diseases, your genes, and diet and the digestive system may make you more likely to develop NAFLD.

Health conditions and diseases

You are more likely to develop NAFLD if you have the following health conditions or diseases

Having more of these health conditions increases your chances of developing NASH. Losing weight may cause NASH to switch to NAFL, and regaining weight may cause NAFL to switch to NASH.


Researchers have found that certain genes may make you more likely to develop NAFLD. These genes may help explain why NAFLD is more common in certain racial and ethnic groups. Experts are still studying the genes that may play a role in NAFLD.

Diet and the digestive system

Researchers are studying whether diets high in fructose—a sugar that is part of table sugar and is also commonly added to sweeten drinks and foods—may increase the risk of NAFLD.

Scientists have also examined the relationship between NAFLD and the microbiome—the bacteria in your digestive tract that help with digestion. Studies have found differences between the microbiomes of people who have NAFLD and those who don’t. Experts are still studying how the microbiome may affect NAFLD.

Is NAFLD the only cause of fatty liver?

Fatty liver may have causes other than NAFLD. If medical tests suggest you have a buildup of fat in your liver, your doctor may ask questions or order tests for other causes.

Alcohol-associated liver disease

Fat may build up in the liver due to alcohol-associated liver disease—damage to the liver and its function due to excessive alcohol consumption. If you have a history of heavy alcohol use and fat in your liver, your doctor may determine you have alcohol-associated liver disease instead of NAFLD.

If you have risks for NAFLD and also drink excessively, you could have both NAFLD and alcohol-associated liver disease at the same time. No tests can easily tell how much each plays a role.

Other causes

Other causes of excess fat in the liver include

Last Reviewed April 2021
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by NIDDK is carefully reviewed by NIDDK scientists and other experts.