Non-alcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) is also known as metabolic dysfunction-associated steatotic liver disease (MASLD). It happens when fat builds up in the cells of your liver. It isn’t caused by drinking too much alcohol. It’s the most common type of liver disease. Most people only have a mild form, which doesn’t usually cause long-term problems. But some people with NAFLD can go on to develop more serious liver damage.

About non-alcoholic fatty liver disease

If your liver is healthy, there should be little or no fat in it. But sometimes, for a variety of reasons, fat can begin to collect in your liver cells. This can sometimes be due to drinking too much alcohol. But if the build-up of fat isn’t linked to alcohol, it’s called non-alcoholic fatty liver disease (NAFLD).

NAFLD is the most common type of liver disease in developed countries and the number of people getting it is rising. Around one in four people have the condition. The chance of getting NAFLD increases with age and the average age of people with it is 53 years. But it’s becoming more common in children and teenagers.

Stages of non-alcoholic fatty liver disease

There are different stages or levels of non-alcoholic fatty liver disease (NAFLD).

• Fatty liver (steatosis). This is when fat builds up in the cells of your liver but doesn’t cause any inflammation. Most people with NAFLD will have this stage.
• Non-alcoholic steatohepatitis (NASH) – also known as metabolic dysfunction-associated steatohepatitis (MASH). This is when the build-up of fat causes your liver to become inflamed and damaged.
• Fibrosis. This is when long-lasting inflammation of your liver causes scar tissue to build up in both your liver and nearby blood vessels. This can affect how your liver works. In the early stages, this might be reversible to some extent.
• Cirrhosis. This is when the long-term scarring to your liver becomes severe and irreversible. Your liver becomes harder and the shape of your liver changes. Cirrhosis can lead to liver failure.

Causes of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is caused by a build-up of fat in your liver. No one is certain why this happens. It may be linked to the way your body responds to the hormone insulin – this is called insulin resistance.

You may be more at risk of getting NAFLD if:

• you’re overweight or obese , especially if you carry extra weight around your middle
• you don’t do much physical activity
• your diet contains foods high in fat and sugar
• you have type 2 diabetes
• you have metabolic syndrome

It’s thought that obesity might be increasing the number of people who are getting NAFLD. Other things that may increase your risk of getting NAFLD include:

• high blood pressure (hypertension)
• high levels of fats in your blood stream – known as hyperlipidaemia
• having an endocrine condition such as polycystic ovary syndrome or hypothyroidism
• other people in your family having NAFLD or the risk-increasing conditions above

Symptoms of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) doesn’t usually cause any symptoms in the early stages. You may only find out you have it if you have a test for something else.

Sometimes, at a later stage, you may get non-alcoholic fatty liver disease symptoms which can include:

• feeling generally unwell and really tired
• pain or discomfort in the upper part of your tummy (abdomen), particularly on the right side, just under your ribs

If the disease progresses further, you may get more NAFLD symptoms, such as:

• itchy skin
• yellow skin and yellow in the whites of your eyes (jaundice)
• swollen legs, ankles, feet or tummy
• unusual marks on your skin, such as red palms, or a mark under your skin (an enlarged blood vessel) that looks like a spider pattern

Diagnosis of non-alcoholic fatty liver disease

You might only find out that you’ve got a problem with your liver when you have a test for another health condition. This might include a blood test or an ultrasound scan of your tummy (abdomen).

If one of these tests shows there might be a problem with your liver, your GP will ask if you have any symptoms and examine you. They’ll ask you about your medical history and your lifestyle, and may weigh you to check your body mass index (BMI). It’s important to be honest about your lifestyle, and about how much and how often you drink alcohol. This will help your GP to make the right diagnosis of the type of fatty liver disease you may have. The GP may wish to do some other tests to check for other possible causes of liver problems.

If your GP suspects you have liver damage, they may refer you to a hepatologist (a doctor who specialises in conditions of the liver).

Blood tests (liver function tests)

Your doctor will give you a blood test and do a liver function test (LFT) to check whether your liver is inflamed or damaged and if it’s working properly. They’ll also check your blood cell count.

If you have non-alcoholic fatty liver disease (NAFLD), your liver function test results may be abnormal. But a normal result doesn’t rule out liver problems. That’s why your doctor may recommend other tests such as an ultrasound scan to help diagnose NAFLD (see below).

Your GP may use the results of blood tests, together with information such as your age and BMI, to assess your risk of liver fibrosis (scarring).

Other tests

You may have one or more of the following tests to help assess the extent of liver damage from NAFLD.

• Transient elastography (a fibroscan). In this test, a doctor or nurse will place a probe over your tummy (like an ultrasound) and move it over your liver. A fibroscan measures the stiffness of your liver to see how much fibrosis (scarring) it has. Some fibroscans can also see how much fat there is in your liver. Alternative options to assess the stiffness of your liver are an acoustic radiation force impulse imaging (ARFI) and an enhanced liver fibrosis (ELF) test.
• A liver biopsy. In this test, your doctor will insert a very fine hollow needle into your liver to collect a small sample of tissue. This is done under local anaesthesia and the sample will be sent to a laboratory to be tested.

If your doctor recommends you have a test, they’ll explain what’s involved and you can ask them questions about it.

Treatment of non-alcoholic fatty liver disease

There aren’t any specific non-alcoholic fatty liver disease (NAFLD) treatments yet. Your doctor will encourage you to make changes to your lifestyle to prevent your condition from getting worse (see our section on self-help and diet for fatty liver disease). Your doctor will also recommend treatment for any medical conditions or complications you may have because of NAFLD.

Medicines

There aren’t any licensed medicines to treat NAFLD yet. There’s lots of research going on to find a treatment, especially for people with the more advanced stages of liver fibrosis and inflammation. There are various medicines that may help to manage any problems associated with NAFLD. For example, your doctor may recommend medicines to treat high blood pressure, high cholesterol, and type 2 diabetes.

Monitoring

If you have NAFLD, your GP will monitor your condition from time to time (probably at least every year). They might refer you to see a specialist for further assessment. This can show if any changes you’ve made to your lifestyle have helped, and make sure your fatty liver doesn’t get any worse. Your GP will examine you and may do some tests, such as taking your blood pressure and measuring your body mass index (BMI). You might need to have some blood tests too.

Your GP or liver specialist may also re-assess your risk of getting liver fibrosis at intervals. They might suggest you have transient elastography (a fibroscan). For more information on fibroscans, see our section on diagnosis of non-alcoholic fatty liver disease.

If you stick with the changes you make to your lifestyle, your liver may improve. If you don’t make any changes, your fatty liver may progress into more serious liver disease and damage.

Surgery

If NAFLD progresses and you develop severe cirrhosis (see our section on stages of non-alcoholic fatty liver disease), your liver may stop working properly. You may need to be put on the waiting list for a liver transplant. If you have other health conditions, such as obesity or cardiovascular issue, your surgeon will need to balance the risks and benefits of the operation.

Complications of non-alcoholic fatty liver disease

Our section on stages of non-alcoholic fatty liver disease (NAFLD) describes the four progressive levels of the disease. Most people just have a fatty liver, and don’t have any long-term effects. But sometimes, the build-up of fat can cause inflammation and scarring, which can lead to the complication of serious liver disease. This can also increase your risk of getting liver cancer.

If you have NAFLD and are obese and/or have diabetes, you may be more at risk of developing cardiovascular disease, such as a heart attack or stroke. Your doctor will check if anything else puts you at risk, and help you to take steps to reduce it. For example, they’ll check your blood pressure and cholesterol levels to see if these are within the normal range. You might need to take medicines to control these.