What is Non-Alcohol Related Fatty Liver Disease (NAFLD)?
This is the name given to a condition in which you have too much fat in your liver. There should be little or no fat in a healthy liver and for most people, carrying a small amount of fat in the liver causes no major problems.
Too much fat in your liver is caused by the build-up of fats called triglycerides. These are the most common fats in our bodies, they belong to a group of fatty, waxy substances called lipids, which your body needs for energy and growth. We get triglycerides from our diet. Foods high in fat and sugar contain high amounts of triglycerides. They can also be made in the liver from sugars and proteins.
The liver processes triglycerides and controls their release. The triglycerides are combined with special proteins to form tiny spheres called lipoproteins which are sent into the bloodstream to circulate among the cells of your body. When the release or ‘secretion’ of lipoproteins from the liver is interrupted or the flow of triglycerides to the liver is increased, there will be a build-up of fat in your liver cells.
Acute Fatty Liver Disease – It is important to differentiate NAFLD and NASH from acute fatty liver disease, which may occur during pregnancy or with certain drugs or toxins (poisons). This condition is very rare and may lead rapidly to liver failure. Please see our Liver Health section for more information.
Consuming too much alcohol can cause an accumulation of fat in the liver and can spur the liver to make triglycerides. If alcohol is the cause of fatty liver disease it is called Alcohol-related fatty liver disease (see our ‘Alcohol and liver disease’ publication).
Fatty liver that is not caused by alcohol is known as Non-Alcohol Related Fatty Liver Disease (NAFLD), which can then lead to Non-Alcohol Related Steatohepatitis (NASH).
Until recently NAFLD was considered to be rare and relatively harmless. It was not thought to progress to chronic (long-term) or serious liver disease. For many people, a fatty liver can remain free of inflammation and they will experience few symptoms.
However, for an increasing number of people, the effects of having fat in their liver, over a long period, may lead to inflammation causing scarring (fibrosis). In some people this can progress to a potentially life-threatening condition known as Cirrhosis.
Today, NAFLD is recognised as one of the most common forms of liver disease worldwide and one that can progress to advanced liver damage.
How does NAFLD affect my liver?
NAFLD is characterised by the build-up of excess fat in the liver of people who do not drink more than recommended guideline amounts of alcohol.
The first stage is fatty liver, or steatosis. This is where fat accumulates in the liver cells without any inflammation or scarring. For many people, the condition will not advance and a serious liver condition will not develop, but for some, NAFLD can progress to NASH.
NASH is a more significant condition, as it may cause scarring to the liver and can progress to cirrhosis. Cirrhosis causes irreversible damage to the liver and is the most severe stage of NAFLD.
It may be easiest to think of NAFLD as having the following stages:
1. Non-alcohol related fatty liver or steatosis
2. Non-alcohol related steatohepatitis (NASH)
3. NASH with fibrosis
How common is NAFLD
NAFLD can affect a wide range of people. In general, the more overweight you are, the more chance there is that you may have the condition. NAFLD is typically seen in people aged around 50 and more commonly in men than women.
It is hard to be precise about how many people have some form of NAFLD but it is estimated that one in five people (20%) in the UK are in the early stages of the condition.
Non-alcohol related steatohepatitis (NASH)
NASH is a more aggressive form of NAFLD where there is inflammation in and around the fatty liver cells. This may cause swelling of your liver and discomfort around it. If you place your right hand over the lower right side of your ribs, it will cover the area of your liver.
Over a long period of time, ongoing inflammation leads to a build-up of scar tissue in your liver. This process is known as fibrosis and can lead to cirrhosis.
NASH is now considered to be one of the main causes of cirrhosis; many cases of cryptogenic (of unknown origin) cirrhosis are now being recognised as being caused by NASH.
Cirrhosis is usually the result of long-term, continuous damage to the liver. This is when irregular bumps, known as nodules, replace the smooth liver tissue and the liver becomes harder. The effect of this, together with continued scarring from fibrosis, means that the liver will run out of healthy cells to support normal functions. This can lead to complete liver failure (please see our ‘Cirrhosis’ page and publication for more information).
What are the causes of NAFLD?
Clinical knowledge about NAFLD is still developing. However, known common risk factors are obesity, lack of physical exercise, insulin resistance, and other features of metabolic syndrome (also known as syndrome X).
People most at risk are those who:
- are overweight or obese
- have a poor diet and do little or no exercise
- have insulin resistance
- have type 2 diabetes
- have hypertension (high blood pressure)
- have hyperlipidaemia (too much cholesterol and triglyceride in their blood)
- have polycystic ovaries
- have hepatitis B
- have hepatitis C
- are taking certain drugs prescribed for other conditions
It is likely there are other factors which contribute to the disease as not everyone with NAFLD exhibits these risk factors.
Metabolic syndrome is defined by the presence of several risk factors associated with an increased risk of cardiovascular disease (CVD); these include insulin resistance, type 2 diabetes, high blood pressure, high triglycerides, low HDL cholesterol and an increased waist circumference (above 102cm in men and 88cm in women).
Very rapid weight loss can also lead to fat building up in the liver. It is thought this may result from the sudden, massive release of free fatty acids into the bloodstream following the breakdown of fat stored in fat cells. This can sometimes follow surgery to reduce obesity, such as a gastric bypass.
More rarely, fatty liver can be associated with other causes such as rare genetic conditions, prolonged fasting, some drug treatments, total parenteral nutrition (intravenous feeding), polycystic ovaries and hepatitis B and C.
The exact cause of progression from NAFLD to NASH and cirrhosis is still unknown.
Fatty liver and obesity
Not everyone who is overweight or obese will develop a fatty liver and not everyone who has a fatty liver is overweight. However, the majority of people with NAFLD are overweight.
As tall people are generally heavier than short people, a person’s weight alone is not particularly useful in assessing their risk of developing a fatty liver or metabolic syndrome. The ratio between height and weight, known as the body mass index (BMI), is a more useful measurement.
Calculating BMI is now the accepted method for working out whether you are a healthy weight, overweight or obese. The terms ‘overweight’ and ‘obese’ describe the two BMI categories above what is considered healthy body size.
A healthy BMI is regarded as being between 18.5 and 25kg/m2. A BMI between 25 and 30kg/m2 is defined as overweight. If your BMI is over 30kg/m2 then you qualify as obese.
Take the NHS Choices Healthy Weight calculator to find out your BMI:
Obesity can also be defined according to the distribution of fat in your body, either, subcutaneous fat (fat under the skin) or visceral fat (intra-abdominal fat). Increased visceral fat is more of a risk factor for NAFLD.
Women have a higher proportion of body fat (about a fifth of their body weight) than men. However, men usually have more visceral fat than women. If you have an ‘apple’ body shape, you will have more fat around your abdomen causing a high release of fatty acids into your circulation. A continued high release of fatty acids can cause insulin resistance and other metabolic complications.
In men, a low risk waist circumference is 94cm (37.6 inches) or below and high risk abdominal obesity is defined as a waist circumference greater than 102cm (40 inches). In women, the equivalent values are a waist circumference lower than 80cm (31.5 inches) and greater than 88cm (35 inches).
There is evidence that people of South Asian origin have a more centralised distribution of body fat (leading to a higher risk of chronic diseases and mortality) even when their waist circumference and BMI are lower than that of their European counterparts. Therefore, a revised BMI range has been recommended for the South Asian population by WHO (World Health Organisation) and the South Asian Health Foundation. If you are South Asian, a BMI above 23kg/m2 is considered to increase your risk of NAFLD.
There are more overweight and obese people in the UK than any other country in Europe.
What are the symptoms?
Most people with mild NAFLD are unlikely to notice any symptoms. Some may experience discomfort n the liver area and tiredness.
For those who go on to develop NASH, Fibrosis and Cirrhosis it may be many years before symptoms develop. The following symptoms may indicate a serious development in your liver condition. Patients with a liver condition who develop any of the following symptoms should see urgent medical attention:
- yellowness of the eyes and skin (jaundice)
- bruising easily
- dark urine
- swelling of the lower tummy area (ascites)
- vomiting blood (haematemesis)
- dark black tarry faeces (melena)
- periods of confusion or poor memory (encephalopathy)
- itching skin (pruritus)
In most cases people only find out they have a fatty liver when a routine blood sample (usually liver function tests) shows there may be a problem. If this happens you may be asked a lot of questions about your lifestyle, such as, any drugs you are taking (including over-the-counter medication and nutritional supplements), your diet, the amount of exercise you do and the amount of alcohol you drink.
Further tests may be needed to confirm the diagnosis such as an Ultrasound, FibroScan, CT or CAT Scan or MRI scan. In some cases a liver biopsy may be needed.
Maintaining a healthy weight through eating a well-balanced diet and taking regular exercise is the best way to prevent NAFLD. The health risks from being overweight or obese can impact on your physical, social and emotional well being. People with NAFLD who go on to develop Cirrhosis are at a higher risk of liver failure.
Although it is not always possible to avoid NAFLD, as some factors such as genetics cannot be prevented, you can significantly reduce your risk by exercising as much as you are able to, and eating healthily to control your weight (see our diet and liver disease information).
Better control of existing medical conditions, such as glucose levels in diabetes, can also help prevent the development of NAFLD and NASH.
There is no specific treatment for NAFLD that all doctors agree on.
However, if your NAFLD is linked to being overweight then you will be advised to make various lifestyle changes including losing weight gradually and taking sensible exercise. There is good evidence that gradual weight loss coupled with increased exercise can reduce the amount of fat in your liver.
In mild cases of NAFLD doctors may concentrate on treating associated conditions, such as obesity and diabetes, which can cause fat to build up. They will also treat disorders such as high blood pressure and high cholesterol as these are often associated with NAFLD.
For full information download the publication below.
Please visit the support section of our website for information on Support groups in your area or visit our Useful Links section for other organisations who may be able to offer information and support.
NICE quality standard and guidance
NICE have published a new quality standard Obesity in adults: prevention and lifestyle weight management programmes. Click here to view.
NICE have also issued a new guideline on how to identify the adults, young people and children with non-alcohol related fatty liver disease (NAFLD) who have advanced liver fibrosis and are most at risk of further complications. It outlines the lifestyle changes and treatments that can manage NAFLD and advanced liver fibrosis.
View references: click here
Reviewed by: Professor Mark Thursz, Professor of Hepatology, Hepatology Section, Division of Medicine, Imperial College, London; Professor Chris Day MA PhD MD FRCP FMedSci Professor of Liver Medicine, Institute of Cellular Medicine, University of Newcastle-upon-Tyne; Dr Phil Newsome PhD FRCPE Senior Lecturer in Hepatology & Consultant Hepatologist, Centre for Liver Research, University of Birmingham.