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Nonalcoholic fatty liver disease (NAFLD)

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Nonalcoholic fatty liver disease (NAFLD) is the term for a wide range of conditions caused by a build-up of fat within the liver cells. It is usually seen in people who are overweight or obese.

A healthy liver should contain little or no fat. Most people with NAFLD only carry small amounts of fat, which doesn't usually cause any symptoms and isn't harmful to the liver. This early form of the disease is known as simple fatty liver, or steatosis.

However, just because simple fatty liver is harmless, it doesn't mean it is not a serious condition:

  • in some people, if the fat builds up and gets worse, it can eventually lead to scarring of the liver
  • as the disease is linked to being overweight or obese, people with any stage of the disease are more at risk of developing a stroke or heart attack

NAFLD is often diagnosed after liver function tests (a type of blood test) produce an abnormal result and other liver conditions, such as hepatitis, are ruled out.

This page explains:

The four stages of NAFLD

NAFLD is very similar to alcoholic liver disease, but it is caused by factors other than drinking too much alcohol. The four stages are described below.

Stage 1: simple fatty liver (steatosis)

Hepatic steatosis is stage 1 of the condition. This is where excess fat builds up in the liver cells but is considered harmless. There are usually no symptoms and you may not even realise you have it until you receive an abnormal blood test result.

Stage 2: nonalcoholic steatohepatitis (NASH)

Only a few people with simple fatty liver go on to develop stage 2 of the condition, called nonalcoholic steatohepatitis (NASH).

NASH is a more aggressive form of the condition, where the liver has become inflamed. Inflammation is the body's healing response to damage or injury and, in this case, is a sign that liver cells have become damaged.

A person with NASH may have a dull or aching pain felt in the top right of their abdomen (over the lower right side of their ribs).

Stage 3: fibrosis

Some people with NASH go on to develop fibrosis, which is where persistent inflammation in the liver results in the generation of fibrous scar tissue around the liver cells and blood vessels. This fibrous tissue replaces some of the healthy liver tissue, but there is still enough healthy tissue for the liver to continue to function normally.

Stage 4: cirrhosis

At this most severe stage, bands of scar tissue and clumps of liver cells develop. The liver shrinks and becomes lumpy. This is known as cirrhosis.

Cirrhosis tends to occur after the age of 50-60, after many years of liver inflammation associated with the early stages of the disease.

People with cirrhosis of the liver caused by NAFLD often also have type 2 diabetes.

The damage caused by cirrhosis is permanent and can't be reversed. Cirrhosis progresses slowly, over many years, gradually causing your liver to stop functioning. This is called liver failure. Learn more about cirrhosis of the liver, including the warning signs.

Who is affected?

You are more likely to develop NAFLD if you:

  • are obese or overweight
  • have type 2 diabetes (this causes an increased uptake of fat into the liver cells)
  • are over the age of 50
  • have high blood pressure
  • have high cholesterol
  • have experienced rapid weight loss, for example after weight loss surgery or after being malnourished

Living with NAFLD

Most people with NAFLD do not develop serious liver problems and just have stage 1 of the disease (simple fatty liver).

Simple fatty liver may go away if the underlying cause is tackled. For example, losing excess weight or controlling diabetes better can make fatty liver go away.

Many people do not have symptoms, although it's common to feel tired and some people have a persistent pain in the upper right part of their abdomen (where their liver is).

It is important to make lifestyle changes to prevent the disease progressing to a more serious stage and to lower your risk of having a heart attack or stroke.

Losing weight and exercising

The most important thing that people with NAFLD can do is to go on a gradual weight loss programme and exercise regularly. This helps in two ways: by reducing the amount of fat in your liver cells and by lowering your risk of stroke and heart attack.

Losing weight is particularly important if you have type 2 diabetes.

Stopping smoking

If you smoke, it's really important to give up, as this will also help to reduce your risk of heart attack and stroke.


If you have high blood pressure or high cholesterol, you may need medical treatment for these. Read about the treatment of high blood pressure and treatment of high cholesterol.

If you have type 2 diabetes, you may need medicines that reduce high levels of blood sugar. At first, this will usually be in the form of tablets, sometimes a combination of more than one type of tablet. It may also include injections of insulin. Learn more about the medical treatment of type 2 diabetes.


NAFLD is not caused by alcohol, but drinking alcohol may make the condition worse. It's therefore advisable to stop drinking alcohol.

Read more about other dietary changes you can make to help with NAFLD.

Content supplied byNHS
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