Fatty liver disease is one of the most common liver conditions in the UK, yet many people live with it for years without knowing. It often causes no obvious symptoms, which makes it easy to miss.
If you have recently been told you have a fatty liver, or you have come across terms like MASLD or NAFLD and are not sure what they mean, this article explains everything clearly.
What Is Fatty Liver Disease?
Fatty liver disease is a condition where too much fat builds up inside the liver. A healthy liver contains a small amount of fat, but when fat makes up more than around five to ten per cent of the liver’s weight, it can start to cause problems.
The condition is not caused by alcohol. It is linked instead to the way the body processes fat and sugar, and to certain health conditions such as obesity and type 2 diabetes.
NAFLD and MASLD: What Is the Difference?
You may have seen both terms used. Here is what they mean and why the name changed.
NAFLD stands for non-alcoholic fatty liver disease. This was the standard medical term used for many years to describe fatty liver disease that is not caused by alcohol.
MASLD stands for metabolic dysfunction-associated steatotic liver disease. This is the updated name, introduced in 2023 by leading liver disease organisations. It better reflects the link between fatty liver and metabolic health conditions such as obesity, high blood sugar, and high blood pressure.
In practice, NAFLD and MASLD describe the same group of people. Studies have shown that nearly all people who would have been diagnosed with NAFLD also meet the criteria for MASLD. The NHS still uses the NAFLD name on its pages, so you may see both terms depending on where you are reading. You can find more detail on the NHS fatty liver disease page.
What Are the Stages of Fatty Liver Disease?
Fatty liver disease can progress through several stages. Most people stay at the first stage without ever developing serious problems, especially with lifestyle changes.
| Stage | Name | What Is Happening |
| 1 | Simple fatty liver (steatosis) | Fat builds up in the liver but causes no damage or inflammation |
| 2 | MASH (previously NASH) | Inflammation develops alongside the fat, which can damage liver cells |
| 3 | Fibrosis | Scar tissue begins to form as a result of ongoing inflammation |
| 4 | Cirrhosis | Extensive scarring that can affect how the liver works |
Most people with fatty liver disease are at stage one. Reaching stage four is uncommon, but the risk is higher if the condition is not managed and underlying health issues are not treated.
What Causes Fatty Liver Disease?
Fatty liver disease is closely linked to metabolic health. The most common causes and risk factors include:
- Obesity, particularly excess fat around the abdomen
- Type 2 diabetes or insulin resistance, where the body struggles to use glucose properly
- High cholesterol or high triglycerides in the blood
- High blood pressure
- A diet high in refined carbohydrates, sugary drinks, and processed foods
- Being physically inactive
It is also possible to develop fatty liver disease without being overweight, though this is less common.
What Are the Symptoms?
This is where fatty liver disease can be difficult to spot. In the early stages, most people have no symptoms at all.
When symptoms do occur, they can include:
- A dull ache or discomfort in the upper right side of the abdomen
- Feeling tired more than usual
- Unexplained weight loss
Because symptoms are often absent or vague, fatty liver disease is frequently found by chance during a blood test or scan done for another reason.
How Is It Diagnosed?
Fatty liver disease is usually picked up through one of the following:
- Blood tests that show raised liver enzymes
- An ultrasound scan of the abdomen
- A FibroScan, which is a special type of scan that checks for liver stiffness and scarring
If your GP suspects fatty liver disease, they may refer you for further tests to check how advanced the condition is.
Can Fatty Liver Disease Be Treated?
There is currently no specific licensed medication for fatty liver disease. Treatment focuses on managing the conditions that cause it.
The most effective steps are:
- Losing weight gradually if you are overweight
- Eating a balanced diet with less sugar, saturated fat, and processed food
- Being more physically active
- Managing type 2 diabetes, high blood pressure, or high cholesterol with your GP’s support
- Avoiding alcohol, which puts additional strain on the liver
These changes can significantly reduce fat in the liver and, in many cases, reverse the condition at its earlier stages.
The Role of Clinical Research
Researchers are working to develop new medicines specifically for MASLD. Clinical trials play an important part in testing whether new treatments are safe and effective.
If you are interested in contributing to this research, you can find out more about the fatty liver disease clinical trial currently open at clinics in London and Manchester.
Taking part in a trial is entirely voluntary. Before you agree to anything, the research team will walk you through everything involved. You can read about what informed consent means to understand your rights as a potential participant.
Trials are also designed with participant safety as a priority. If you would like to know more about the safeguards in place, you can read about how clinical trials keep participants safe.
Travel expenses are covered for all participants taking part in a 4MCS trial. Participation does not involve any payment.
Key Points to Remember
- Fatty liver disease occurs when too much fat builds up in the liver, unrelated to alcohol
- MASLD is the updated medical term for what was previously called NAFLD
- Most people have no symptoms, and the condition is often found by chance
- The main causes are obesity, type 2 diabetes, and poor metabolic health
- Lifestyle changes are the most effective way to manage the condition
- Clinical research is ongoing to find new treatments
