A person’s liver usually contains a small amount of fat. However, nonalcoholic fatty liver disease (NAFLD) is where an individual has a store of excess fat in their liver. It does not result from alcohol use.

There are two types of NAFLD: nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH).

Weight loss is the only recommended treatment for NAFLD, and there are currently no medications to treat either condition.

Read on to find out the symptoms, causes, and treatments of NAFLD, NAFL, and NASH and the differences between the three.

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According to the American Liver Foundation (ALF), the liver typically contains a small amount of fat.

However, fatty liver occurs when more than 10% of this organ’s weight comprises fat.

NAFLD is the most common cause of chronic liver disease in the United States and affects up to 25% of the world’s population.


NAFLD is known as a silent disease, meaning that usually there are no symptoms of the condition.

However, some people may experience symptoms such as:

  • abdominal pain
  • fatigue
  • jaundice
  • loss of appetite
  • mental confusion
  • nausea
  • swelling in the legs and abdomen
  • weakness
  • weight loss


The ALF estimates that around 100 million people in the U.S. have NAFLD. However, health experts do not fully understand what causes the condition. Studies are continuing, but researchers have concluded that certain health conditions may contribute to the development of NAFLD. A person’s genetic makeup, diet, and digestive system may also play a role.

Health conditions that may make an individual more likely to develop NAFLD include:

And while researchers believe specific genes may contribute to developing this condition, further studies are necessary.

As well as the above, certain herbal remedies or dietary supplements can cause damage to the liver, so anyone who wishes to start taking supplements should always discuss the risks with their doctor.


A person can control or even reverse NAFLD through healthy living, which may involve following a nutritious diet or losing weight. Experts suggest losing weight can help reduce fat in the liver as well as reduce inflammation and fibrosis.


If healthcare providers suspect a person has NAFLD, NAFL, or NASH, they may order various tests to confirm. These may include:

  • a medical history
  • blood tests
  • imaging tests
  • a liver biopsy

Also known as simple fatty liver, NAFL occurs when there is a mainly harmless build-up of fat in the liver. It is known as steatosis.

According to the United Kingdom’s National Health Service (NHS), most people will only ever develop NAFL and not usually realize it.

However, NAFL may progress for some individuals and cause liver damage.


NAFL typically does not cause liver inflammation or damage. However, because the liver may be larger than usual due to the additional fat in the organ’s cells, people may experience pain. Usually, NAFL will not progress.


Fatty liver is not necessarily due to NAFLD. Doctors may wish to look into alternative diagnoses before settling on NAFLD as the cause of a person’s fatty liver.

For example, fatty liver can also be due to:

  • alcohol-associated liver disease
  • losing weight too quickly
  • taking certain medications
  • toxin exposure
  • Wilson’s disease or other rare genetic diseases


According to the National Institute of Diabetes and Digestive and Kidney Diseases, it may be possible to prevent or minimize a person’s risk of developing NAFLD with lifestyle changes.

These include:

  • regular physical activity
  • maintaining a moderate weight
  • following a nutritious diet
  • limiting portion sizes

Often, losing between 3% and 5% of a person’s body weight can reduce fat in the liver.


As there are no symptoms, doctors usually only discover NAFL when carrying out medical tests for other reasons. For example, a blood test will show high levels of liver enzymes. Healthcare professionals may then wish to carry out further investigations, such as a complete medical history and physical examinations.

If a person has NASH and high levels of fat in their liver, they also have inflammation and liver damage.

This inflammation and liver damage can lead to:


Again, there are often no symptoms for NASH, but some people may develop cirrhosis as a complication.

Symptoms of cirrhosis include:

  • being quick to bruise and bleed
  • intense itching
  • jaundice, which refers to yellowing of the eyes and skin
  • spider veins, which are visible blood vessels close to the surface of the skin
  • swelling in the abdomen

It is essential to seek urgent medical attention if a person experiences any of the following symptoms:

  • fever
  • shortness of breath
  • vomiting blood
  • dark or black tarry stools
  • slurred speech, and mental confusion

Without treatment, cirrhosis can cause the liver to stop functioning: A range of different health issues can result from the liver not working correctly, as it controls so many other bodily functions.


The ALF estimates that about 20% of people with NAFLD will develop NASH. Older individuals are also more likely to develop NASH, but some children may get it.

NASH is also more likely to occur in people with:

  • excess weight or obesity
  • body fat concentrated around the waist
  • insulin resistance or type 2 diabetes
  • high blood pressure
  • obstructive sleep apnea


To reduce liver inflammation and fibrosis, people should aim to lose between 7% to 10% of their body weight. Health experts recommend doing this over time rather than rapidly, as losing weight too quickly can worsen liver disease.

Doctors may use medications to treat complications of NASH, which may require minor medical procedures or surgery. People experiencing liver failure or liver cancer may need a liver transplant.


A liver biopsy is the only test that can diagnose NASH, as it needs to show precisely how far the condition has progressed. Liver biopsies can rule out other conditions or give healthcare providers a better view of advanced liver disease or cirrhosis than imaging tests can.

Full nameNonalcoholic fatty liverNonalcoholic steatohepatitis
Excess fat in the liverYesYes
Liver damageNoYes
ReversibleUsuallyDepends on progression
Treatment3–5% body weight loss7–10% body weight loss
Possible complicationsTypically noneFibrosis, cirrhosis, liver cancer, liver failure

NAFL, NAFLD, and NASH are connected, in that NAFL and NASH are both types of NAFLD.

While NAFL is easily treatable and reversible, NASH may advance to a stage where all a person can do is prevent further damage.

Slowly and steadily losing weight is the best treatment for all forms of nonalcoholic fatty liver conditions.