Symptoms & Causes of NAFLD & NASH

What are the symptoms of NAFLD?

Usually, nonalcoholic fatty liver disease, or NAFLD (also referred to as metabolic dysfunction-associated steatotic liver disease, or MASLD), is a silent disease with few or no symptoms. You may not have symptoms even if you develop cirrhosis due to nonalcoholic steatohepatitis, or NASH (also referred to as metabolic dysfunction-associated steatohepatitis, or MASH).

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

• overweight or obesity
• insulin resistance or type 2 diabetes
• abnormal levels of fats in your blood, which may include
  • high levels of triglycerides
  • abnormal levels of cholesterol—high total cholesterol, high LDL cholesterol, or low HDL cholesterol
• metabolic syndrome or one or more traits of metabolic syndrome. Metabolic syndrome is a group of traits and medical conditions linked to overweight and obesity. Doctors define metabolic syndrome as the presence of any three of the following
  • large waist size
  • high levels of triglycerides in your blood
  • low levels of HDL cholesterol in your blood
  • high blood pressure
  • higher than normal blood glucose levels or a diagnosis of type 2 diabetes

Having more of these health conditions increases your chances of developing NASH. Losing weight may cause NASH to switch to nonalcoholic fatty liver, or NAFL (also referred to as metabolic dysfunction-associated steatotic liver, or MASL), and regaining weight may cause NAFL to switch to NASH.

Genes

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

• disorders, called lipodystrophies, that cause your body to use or store fat improperly
• rapid weight loss or malnutrition
• some medicines, including corticosteroids, HIV treatment, estrogens, certain medicines used to treat cancer, and others
• exposure to some toxins
• rare genetic diseases, such as Wilson disease and hypobetalipoproteinemia