Understanding Non-Alcoholic Fatty Liver Disease

MASLD is the current name for fatty liver disease linked to metabolism, a condition in which extra fat builds up in the liver, and it is the same condition that used to be called NAFLD [1,9].

This page provides general information. It does not replace advice from a doctor or another qualified healthcare professional.

Key facts

NAFLD was renamed MASLD in 2023. It is the same condition, and both names are still in everyday use [1,9].
MASLD is very common. Around 32 percent of adults worldwide are estimated to have it, and it is the most common long-term liver condition in the world [15,16].
Most people with MASLD never develop serious liver damage. Out of every 100 people with early-stage MASLD, 70 to 90 do not go on to develop advanced scarring [13].
MASLD is usually silent and is often found by accident, during tests done for something else [4,15].
Body weight is part of the picture and not the whole picture. Almost a fifth of people with this condition have a body mass index in the healthy range [17].
For most people with MASLD, the greatest risk to overall health is heart disease rather than liver disease [6,13].

What is MASLD?

MASLD stands for metabolic dysfunction-associated steatotic liver disease. It means extra fat has built up inside the liver in someone who also has at least one feature of poor metabolic health, such as raised blood sugar, raised blood pressure, a larger waist or abnormal blood fats [1,2]. Metabolism is the way the body takes energy from food and stores it. Doctors use the label when more than 5 percent of liver cells contain fat [10].

If you searched for NAFLD, you are in the right place

NAFLD, non-alcoholic fatty liver disease, is the former name for MASLD. They are the same condition, and so is the everyday phrase fatty liver disease [9]. Older leaflets, results and conversations will use NAFLD for years yet, and Liver UK puts it simply: use whichever name you feel most comfortable with [9].

What changed in 2023, and why

In 2023 a consensus led by three international liver associations, involving 236 panelists from 56 countries, replaced the old names [1]. The old label described the condition by what it was not, and it used words people found upsetting: “nonalcoholic” was felt to be stigmatizing by 61 percent of those asked, and “fatty” by 66 percent [1,9].

The definition changed too. MASLD is now diagnosed by what is present, liver fat plus at least one of five cardiometabolic features, rather than by ruling other things out [1,2].

The spectrum, from fat alone to cirrhosis

MASLD is not one fixed state. Doctors describe it in stages based on scarring, called fibrosis [13]:

Stage	What it means
Stage 0, simple fatty liver	Extra fat, no inflammation, no scarring. The liver works normally and this stage can be fully reversed.
Stage 1, mild fibrosis	Inflammation has caused a small amount of scarring.
Stage 2, moderate fibrosis	More scarring. The liver usually still works well and most damage can be repaired.
Stage 3, advanced fibrosis	More scarring again, though the liver should still be working.
Stage 4, cirrhosis	Large parts of the liver are scarred. It may keep working, or it may struggle.

Most people sit at stage 0. Having one stage does not mean moving to the next, and progression usually takes years or decades [13]. Out of every 100 people with early-stage MASLD, 10 to 30 develop advanced scarring and 70 to 90 do not [13].

Where MASH fits

MASH, metabolic dysfunction-associated steatohepatitis, is the more serious form, where fat is joined by inflammation and injury to liver cells, and it drives the scarring [6]. See the trialport guide to MASH.

How common is it?

Around 32 percent of adults worldwide are estimated to be living with MASLD, and it is now the most common long-term liver condition globally [15,16]. Estimates have climbed over time, from around 25 percent in pooled data up to 2015 to around 38 percent for 2016 to 2019 [15].

These are estimates rather than counts. There is no simple test for MASLD, many people never know they have it, and studies use different methods, so figures vary [4,12]. Numbers also differ by region: around 30 percent across the European Union and the United Kingdom, around 25 percent in western Europe, around 44 percent in Latin America [15,16], around 31 percent in Asia and around 43 percent in the Middle East and North Africa [18]. Liver UK estimates around 1 in 4 adults in the United Kingdom, of whom about 1 in 20 has advanced scarring, and Australia’s liver charity estimates about 1 in 3 adults there has some form of fatty liver disease [9,19].

Rates run higher in some groups. Around 65 to 75 percent of people living with obesity or type 2 diabetes are affected [15].

What causes it?

MASLD begins when something goes wrong with the way the body uses and stores energy, so fat collects inside liver cells and irritates them. The liver keeps repairing itself, and the repair material is left behind as scar tissue [10].

Several things raise the chance of developing it: overweight or obesity, insulin resistance or type 2 diabetes, raised triglycerides or abnormal cholesterol, and high blood pressure [7]. Risk also rises with age and is higher in men [10]. Genes matter too. A gene is a set of instructions inside cells, and small differences in certain genes make MASLD more likely, though they are not enough on their own to cause it [7,15].

Body weight is part of the picture and not the whole picture. A global review of 93 studies covering more than 10 million people found that almost a fifth of those affected were lean [17]. Nobody chooses to develop MASLD, and weight is shaped by far more than personal choices, including where people live and work and the cost of food [10].

Where alcohol fits, and what MetALD means

MASLD is defined by metabolic features, and heavy drinking is a separate cause of fat in the liver [1,7]. The 2023 consensus created a category for the overlap, called MetALD, covering people who have the metabolic features of MASLD and also drink more than the MASLD definition allows [1]. The thresholds are set in grams per week and differ for women and men, so a doctor works out which fits [1]. Both causes can be present at once.

What are the symptoms?

Most people with MASLD have no symptoms at all, often for years, and symptoms usually appear only after the liver has already been damaged [11]. You cannot tell whether you have it by how you feel, and a person can even have cirrhosis and still feel well [7,11].

Where early symptoms do appear, they are vague: tiredness, a general lack of energy, or discomfort in the upper right side of the abdomen where the liver sits [7,11]. None is specific to the liver.

When to seek urgent help. These symptoms belong to advanced liver disease, and most people with MASLD will never experience them. Tell a doctor straight away if any appear: yellowing of the skin or the whites of the eyes, which is harder to see on black or brown skin; vomiting blood; black, tarry stools; confusion, memory problems or unusual changes in mood; swelling of the abdomen, legs, ankles or feet; bruising easily; dark urine; itchy skin; or losing weight without trying [11].

How is it diagnosed?

There is no single test for MASLD, which is why it is often missed [12]. Most cases are found by accident, when liver blood tests or an ultrasound are done for some other reason [4,15].

Blood tests, with an important caveat. Raised liver enzymes can be a clue, and normal ones prove nothing. More than 80 percent of people with MASLD have normal routine liver blood tests, and United Kingdom guidance says plainly that those tests should not be used to rule MASLD out, nor to check for scarring [3,4].

Fibrosis scores. Rather than looking at one result, doctors combine several into a score. FIB-4 uses two liver enzymes, the platelet count and age. The enhanced liver fibrosis test measures three substances linked to scarring, and United Kingdom guidance treats a score of 10.51 or above as advanced fibrosis [3,12].

Scans. An ultrasound shows fat, since a fatty liver looks brighter than a healthy one. Transient elastography, often called FibroScan, is a quick painless scan that measures liver stiffness, which reflects scarring [12].

What happens next. Initial testing points to one of three outcomes: low risk, where a family doctor continues care and repeats a fibrosis test every few years; an unclear result needing further tests; or high risk, meaning referral to a liver specialist called a hepatologist [3,12]. A liver biopsy, in which a needle takes a tiny sample for examination, is used only when tests and scans leave the picture unclear [12].

How is it treated?

Treatment has two aims: to stop the condition getting worse, and to help the liver repair what it can [14]. There is no cure in the sense of a single course of treatment, though MASLD can improve and sometimes reverse, especially early on [13,14].

Heart health usually comes first. Whatever stage the liver is at, the greatest risk to overall health is often heart attack and stroke, and cardiovascular disease is the most common cause of death in people with this condition [6,13]. Managing type 2 diabetes, blood pressure and cholesterol is therefore central rather than secondary [3,13].

Everyday changes. Liver UK puts the encouraging version plainly: no matter what you weigh, improving diet and activity levels can lower the amount of fat in the liver [14]. There is no special diet that cures MASLD, and physical activity reduces liver fat even without weight loss [3,8,14]. Where weight loss is part of the plan, it should be gradual, since rapid loss can make liver disease worse, and a doctor can refer someone to a dietitian or local program [8,14].

Medicines. No medicine treats MASLD as a whole. Two have been approved in some countries for MASH with moderate to advanced scarring, which the MASH guide covers [2,16]. United Kingdom guidance advises staying within national low-risk limits for alcohol, and stopping completely where advanced fibrosis or cirrhosis is present [3,14].

Living with MASLD

Monitoring continues even when nothing feels wrong, because the condition is silent [11,12]. Stopping smoking helps, since smoking speeds liver disease up and raises the risk of liver cancer [14]. Some herbal remedies and supplements can damage the liver, so check with a doctor before taking them [8]. A diagnosis that carries assumptions about weight and drinking can be hard to talk about, and liver charities run free nurse-led helplines for exactly this.

Thinking about a clinical trial?

Clinical trials test whether a treatment works and is safe. Deciding whether to look into one is personal, and it helps to take it in steps.

1. Understand what the study is asking

It is worth being clear on what a study involves:

what the researchers are trying to learn, and whether it concerns the liver, the heart, or both
what is being studied, and what it is compared with
how long it lasts, and whether there is follow-up afterward
what visits and tests are involved, how far you would travel, and how often
the possible benefits, the known and unknown risks, and what happens at the end

Studies here often run a year or longer, because liver changes are slow. Not all test medicines: some test better ways to find the condition earlier.

2. Consider possible medical suitability

Every trial has rules about who can take part, called eligibility criteria. For a study in this condition they might include liver fat confirmed on a scan, at least one cardiometabolic feature such as type 2 diabetes or raised blood pressure, a fibrosis stage or liver stiffness reading inside a stated range, alcohol below a stated limit, no other cause of liver disease, and a steady dose of current medicines. Some studies now recruit across all body mass index ranges, since obesity is not the only route into this condition [17].

trialport’s medifit helps people consider information related to possible medical suitability. It does not diagnose a condition, confirm eligibility or replace formal screening by the study team.

Explore MASLD clinical trials through trialport

3. Consider whether participation fits your life

A study can look right on paper and still be hard in practice. Worth thinking through:

the time each visit takes, and how many there are in total
how fasting blood tests and scans would fit around work, school or caring for other people
travel, distance and who would come with you
how you would feel about being weighed and asked about food, activity and alcohol at every visit
whether a study asks you to change daily routines, and whether that is realistic now
who supports you, and whether you understand the study well enough to decide

trialport’s readifit helps people reflect on their understanding, motivation, time, routines, support, emotions and practical arrangements.

4. Ask questions before deciding

Useful questions to put to a research team:

Why is this study being carried out, and what is already known?
What would I need to do, and for how long?
What are the known risks and side effects, and what is still unknown?
Could I receive a placebo? A placebo is a dummy treatment with no active medicine, used so researchers can compare results fairly. Would I still receive usual care alongside it?
What tests would I have, and would any involve a biopsy?
Would my current medicines for diabetes, blood pressure or cholesterol be changed?
What would I be told about alcohol, and what if I find that hard?
Will I be told my own scan and fibrosis results?
Can I leave after joining, and what happens to my care if I do?

Taking part is voluntary. A person can ask questions, speak with people they trust and choose not to participate.

Search for clinical trials at app.trialport.com.

Current research

Finding the condition earlier and without a biopsy. United Kingdom guideline authors call this an urgent need, both for spotting MASLD in the huge numbers of people at risk and for identifying inflammation without an invasive test [4].
Working out who will get worse. Researchers are testing how well repeated fibrosis scores track progression in an individual, which is still unsettled [15].
Treating the whole picture, not only the liver. Newer work looks at whether treatment reduces heart and kidney complications as well as liver scarring [15,16].

Study status checked: 3 August 2026. Research moves quickly and what is being studied changes, so this list will date. For current information, search at app.trialport.com.

Support and further information

In the United Kingdom, Liver UK, formerly the British Liver Trust, has the clearest patient information on this condition and a free nurse-led helpline [9,14], and NICE guideline NG49 sets out what care should look like [3]. In the United States, the NIDDK pages on fatty liver disease are detailed and government-reviewed, though last reviewed in 2021 and so predating the renaming [6,8]. In Australia, the Liver Foundation covers the same ground for an Australian reader [19]. Coverage is thinner elsewhere, and a hospital liver clinic is the best starting point.

Questions people often ask

Is NAFLD the same as MASLD?
Yes. NAFLD was renamed MASLD in 2023, and fatty liver disease is the everyday phrase for the same thing. Most people surveyed found the words “nonalcoholic” and “fatty” stigmatizing [1,9].

Is fatty liver disease serious?
For most people it does not become serious. Out of every 100 people with early-stage MASLD, 70 to 90 never develop advanced scarring [13]. A smaller group does, which is why testing is offered.

What is the difference between MASLD and MASH?
MASLD is the umbrella: fat in the liver alongside metabolic features. MASH is the form where inflammation and liver-cell injury are present too, and it drives scarring [2,6].

Can I have this if I am not overweight?
Yes. A global review found that almost a fifth of people with this condition were lean and around 40 percent were not obese [17].

Is it caused by drinking?
No. MASLD is defined by metabolic features, and its definition sets a limit on alcohol. Where metabolic risk and higher alcohol intake are both present, doctors use the separate category MetALD [1].

Can it be reversed?
Often, yes, especially early on. Stage 0 can be fully reversed, and diet and activity can repair some damage at later stages too [13,14].

Did I bring this on myself?
No. Nobody chooses to develop this condition, weight is shaped by far more than personal choices, and almost a fifth of people affected have a body mass index in the healthy range [10,17].

Sources

Rinella ME, Lazarus JV, Ratziu V, et al. A multisociety Delphi consensus statement on new fatty liver disease nomenclature. Journal of Hepatology. 2023;79(6):1542-1556. doi:10.1016/j.jhep.2023.06.003. Abstract read via the Europe PMC public interface: https://europepmc.org/article/MED/37364790 Accessed 3 August 2026.
European Association for the Study of the Liver, European Association for the Study of Diabetes, European Association for the Study of Obesity. EASL-EASD-EASO Clinical Practice Guidelines on the management of metabolic dysfunction-associated steatotic liver disease (MASLD). Journal of Hepatology. 2024;81(3):492-542. doi:10.1016/j.jhep.2024.04.031. Abstract read via the Europe PMC public interface: https://europepmc.org/article/MED/38851997 Accessed 3 August 2026.
National Institute for Health and Care Excellence. NICE guideline NG49, Metabolic dysfunction-associated steatotic liver disease (MASLD). Published 6 July 2016, last updated 31 July 2026. Guideline overview and recommendations 1.1 to 1.6. https://www.nice.org.uk/guidance/ng49 Accessed 3 August 2026.
National Institute for Health and Care Excellence. NICE guideline NG49, Recommendations for research. https://www.nice.org.uk/guidance/ng49/chapter/Recommendations-for-research Accessed 3 August 2026.
National Institute for Health and Care Excellence. NICE guideline NG49, Terms used in this guideline. https://www.nice.org.uk/guidance/ng49/chapter/Terms-used-in-this-guideline Accessed 3 August 2026.
National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health. Definition & Facts of NAFLD & NASH. Last reviewed April 2021. https://www.niddk.nih.gov/health-information/liver-disease/nafld-nash/definition-facts Accessed 3 August 2026.
National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health. Symptoms & Causes of NAFLD & NASH. Last reviewed April 2021. https://www.niddk.nih.gov/health-information/liver-disease/nafld-nash/symptoms-causes Accessed 3 August 2026.
National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health. Treatment for NAFLD & NASH. Last reviewed April 2021. https://www.niddk.nih.gov/health-information/liver-disease/nafld-nash/treatment Accessed 3 August 2026.
Liver UK. What is MASLD? Last updated June 2026. https://liveruk.org/about-liver-disease/conditions/masld/what-is-masld/ Accessed 3 August 2026.
Liver UK. What causes MASLD? Last updated June 2026. https://liveruk.org/about-liver-disease/conditions/masld/what-causes-masld/ Accessed 3 August 2026.
Liver UK. What are the symptoms of MASLD? Last updated June 2026. https://liveruk.org/about-liver-disease/conditions/masld/what-are-the-symptoms-of-masld/ Accessed 3 August 2026.
Liver UK. How is MASLD diagnosed? Last updated June 2026. https://liveruk.org/about-liver-disease/conditions/masld/how-is-masld-diagnosed/ Accessed 3 August 2026.
Liver UK. What are the stages of MASLD? Last updated June 2026. https://liveruk.org/about-liver-disease/conditions/masld/what-are-the-stages-of-masld/ Accessed 3 August 2026.
Liver UK. How is MASLD treated? Last updated June 2026. https://liveruk.org/about-liver-disease/conditions/masld/how-is-masld-treated/ Accessed 3 August 2026.
Reinson T, Bilson J, Childs C, Buchanan RM, Targher G, Byrne CD. Metabolic dysfunction associated steatotic liver disease: mechanisms, diagnosis, and management in adults. BMJ Medicine. 2026;5(1):e002038. doi:10.1136/bmjmed-2025-002038. https://pmc.ncbi.nlm.nih.gov/articles/PMC13052820/ Accessed 3 August 2026.
Lazarus JV, White TM, Agirre-Garrido L, et al. Assessing Europe’s policy readiness to confront the MASLD/MASH public health threat. The Lancet Regional Health – Europe. 2026;65:101713. doi:10.1016/j.lanepe.2026.101713. https://pmc.ncbi.nlm.nih.gov/articles/PMC13245526/ Accessed 3 August 2026.
Ye Q, Zou B, Yeo YH, et al. Global prevalence, incidence, and outcomes of non-obese or lean non-alcoholic fatty liver disease: a systematic review and meta-analysis. The Lancet Gastroenterology & Hepatology. 2020;5(8):739-752. doi:10.1016/S2468-1253(20)30077-7. Abstract read via the Europe PMC public interface: https://europepmc.org/article/MED/32413340 Accessed 3 August 2026.
Henry L, Paik J, Younossi ZM. Review article: the epidemiologic burden of non-alcoholic fatty liver disease across the world. Alimentary Pharmacology & Therapeutics. 2022;56(6):942-956. doi:10.1111/apt.17158. Abstract read via the Europe PMC public interface: https://europepmc.org/article/MED/35880713 Accessed 3 August 2026.
Liver Foundation (Australia). Fatty liver disease. https://liver.org.au/your-liver/liver-diseases/fatty-liver-disease/ Accessed 3 August 2026.

Review information

Written by: trialport editorial team
Reviewed by: Keith Berelowitz, Founder and CEO, trialport
Reviewed on: 3 August 2026
Next review due: 3 August 2027
References last checked: 3 August 2026

MASLD, formerly NAFLD: a plain-language guide