What fatty liver disease actually is, why so many people have it without knowing, and what the evidence says about reversing it
MASLD — Metabolic dysfunction-Associated Steatotic Liver Disease — is the current name for what most people know as fatty liver disease, previously called NAFLD (non-alcoholic fatty liver disease). The name changed in 2023 to better reflect the underlying metabolic causes. If you were told you have a fatty liver, NAFLD, or MASLD — these refer to the same spectrum of conditions.
At its simplest, MASLD means that excess fat has accumulated in the liver — in people who drink little or no alcohol. The liver is not supposed to store significant amounts of fat. When it does, the result is a condition that ranges from completely silent and reversible at one end, to serious, progressive liver disease at the other.
MASLD is not a single condition. It describes a spectrum that progresses through several stages — though many people never progress beyond the earliest.
| Stage | What it means | Typical outcome |
|---|---|---|
| Steatosis (simple fatty liver) | Fat accumulation in liver cells, no significant inflammation | Often stable or reversible with lifestyle change |
| MASH (Metabolic dysfunction-Associated SteatoHepatitis) | Fat plus inflammation and liver cell damage — previously called NASH (non-alcoholic steatohepatitis) | Can progress to fibrosis (scarring) if untreated |
| Fibrosis | Scar tissue forming in the liver as a result of repeated inflammation | Reversible at early stages with significant intervention |
| Cirrhosis | Advanced scarring — liver architecture permanently disrupted | Largely irreversible; risk of liver failure and cancer rises significantly |
| Hepatocellular carcinoma (HCC — primary liver cancer) | Primary liver cancer arising from MASLD-related damage | Serious — MASLD is a leading cause of liver cancer in the UK |
MASLD develops when the liver accumulates more fat than it can process. This happens against a background of metabolic dysfunction — disrupted insulin (the hormone that controls blood sugar) signalling, excess calorie intake, and impaired fat metabolism. The key risk factors are well established:
MASLD is often picked up incidentally — on an ultrasound done for another reason, or when a routine blood test shows mildly elevated liver enzymes (ALT — alanine transaminase — or AST — aspartate transaminase). Many GPs now proactively screen people with known risk factors: obesity, type 2 diabetes, or metabolic syndrome.
The EASL/EASD/EASO 2024 guidelines recommend a structured two-step approach to assess how serious the MASLD is — specifically, to identify whether significant fibrosis (scarring) is present.
| Step | Test | What it shows |
|---|---|---|
| Step 1 | FIB-4 score (blood test calculation) | Estimates fibrosis risk using age, AST, ALT, and platelet count. Score <1.3 = low risk. Score >2.67 = high risk (specialist referral). 1.3–2.67 = indeterminate → proceed to step 2 |
| Step 2 | Transient elastography (FibroScan) | Measures liver stiffness non-invasively — a proxy for fibrosis. Avoids liver biopsy in most cases. Liver stiffness <8 kPa (kilopascals — a measure of stiffness) = low risk. >12 kPa = high risk |
| If needed | Liver biopsy | Definitive assessment of fibrosis stage and presence of MASH. Reserved for cases where non-invasive tests are indeterminate or results would change management |
| Imaging | Ultrasound | Can detect moderate-to-severe steatosis but is not sensitive enough to detect early fat accumulation or fibrosis |
There is currently no licensed pharmacological treatment specifically for MASLD in the UK. A NICE technology appraisal for resmetirom (Rezdiffra) is awaiting development. Semaglutide (Ozempic, Wegovy) and other GLP-1 receptor agonists (medications that mimic a gut hormone to lower blood sugar and reduce appetite) are showing significant promise in clinical trials and may be prescribed for their licensed indications of obesity or type 2 diabetes, with MASLD benefit as an additional effect.
For the vast majority of people with MASLD, lifestyle intervention is both the first-line and the most effective treatment available.
These thresholds are the most important numbers in MASLD management. They come from multiple randomised trials and are endorsed by the EASL/EASD/EASO 2024 guidelines. The key message: even modest, sustained weight loss makes a clinically meaningful difference.
The Mediterranean dietary pattern has the strongest evidence base for MASLD — reducing liver fat and improving insulin sensitivity (the body's ability to respond to insulin) across multiple randomised trials. Specific targets include: reducing ultra-processed food, added sugar (especially fructose-containing drinks and foods), and refined carbohydrates; increasing vegetables, legumes, fish, and olive oil.
Physical activity improves liver fat and insulin resistance independently of weight loss. Both aerobic exercise (sustained activity that raises heart rate) and resistance training (working muscles against a load) are effective. The EASL guidelines recommend at least 150–300 minutes of moderate-intensity activity per week.
The joint European guidelines for MASLD management, published in the Journal of Hepatology in June 2024, represent the most comprehensive and up-to-date evidence synthesis available. They define MASLD as steatotic liver disease in the presence of at least one cardiometabolic risk factor and the absence of harmful alcohol intake. Key recommendations include: FIB-4 as first-line fibrosis assessment; lifestyle modification as the primary treatment; GLP-1 receptor agonists (medications that mimic a gut hormone to lower blood sugar and reduce appetite) for eligible patients with obesity or type 2 diabetes; and consideration of resmetirom (Rezdiffra) for non-cirrhotic MASH with significant fibrosis (stage ≥2) where locally approved.
EASL; EASD; EASO. 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
Multiple randomised controlled trials and systematic reviews have established the dose-response relationship between weight loss and liver outcomes in MASLD. Sustained weight loss of ≥5% reduces hepatic steatosis (liver fat), ≥7% improves necroinflammation (liver cell inflammation and damage — the activity component of MASH), and ≥10% stabilises or reverses fibrosis (scarring) — including at F2–F3 stage. These thresholds form the basis of clinical guidance worldwide and are endorsed by the EASL 2024 guidelines. The challenge is sustaining the weight loss: trials consistently show that the benefit is maintained only while the weight loss is maintained.
Romero-Gómez M, Zelber-Sagi S, Trenell M. Treatment of NAFLD with diet, physical activity and exercise. Journal of Hepatology 2017;67(4):829–846. DOI: 10.1016/j.jhep.2017.05.016
A randomised controlled trial involving 259 participants with MASLD found that a 12-week Mediterranean diet intervention reduced hepatic steatosis by 39% and improved insulin sensitivity compared to a standard low-fat diet. The Mediterranean pattern — high in vegetables, legumes, fish, olive oil, and whole grains, low in red and processed meat and added sugars — consistently outperforms other dietary patterns in MASLD trials, likely through its combined effects on insulin resistance (the body's reduced ability to respond to insulin), inflammation, and gut microbiome composition (the community of bacteria in the gut).
Evidence synthesised from multiple RCTs reviewed in: Karimi F, et al. Dietary Interventions in Metabolic Dysfunction-Associated Steatotic Liver Disease: A Narrative Review. International Journal of Molecular Sciences 2025;26(19):9625. DOI: 10.3390/ijms26199625
A report from the British Liver Trust published in June 2025 highlighted critical gaps in MASLD diagnosis and care in the UK. MASLD is estimated to affect up to 1 in 5 people in the UK — approximately 10 million people — yet the vast majority remain undiagnosed. Diagnosed prevalent cases were estimated at approximately 5.2 million in 2024, meaning roughly half of those affected are unidentified. The report called for MASLD to be given the same clinical attention as other major chronic conditions, and raised serious concerns about NHS capacity to manage the growing patient population.
British Liver Trust. Urgent action needed as new research reveals gaps in fatty liver disease diagnosis and care. Published June 2025. Based on GlobalData epidemiological analysis of UK MASLD prevalence 2024–2032.
The ESSENCE trial is a phase 3 randomised controlled trial of semaglutide (Ozempic, Wegovy) 2.4mg once weekly versus placebo in 800 adults with biopsy-confirmed MASH and stage 2 or 3 fibrosis (liver scarring). Published in the New England Journal of Medicine in April 2025. At 72 weeks, the first co-primary endpoint showed 62.9% of people on semaglutide achieved resolution of steatohepatitis (liver cell inflammation and damage) with no worsening of fibrosis, compared to 34.3% on placebo — an estimated difference of 28.7% (95% CI — confidence interval — the range within which the true value most likely falls — 21.5–35.7%). The second co-primary endpoint (fibrosis improvement with no worsening of steatohepatitis) was also met. Part 2 of the trial continues, with results expected 2029. GLP-1 receptor agonists are not yet licensed specifically for MASLD in the UK but may be prescribed for obesity or type 2 diabetes in eligible patients.
Sanyal AJ, Newsome PN, Kliers I, et al. Phase 3 Trial of Semaglutide in Metabolic Dysfunction-Associated Steatohepatitis. New England Journal of Medicine 2025;392(17):1607–1619. DOI: 10.1056/NEJMoa2413258
MASLD is one of the most common chronic conditions in the UK — and one of the most under-recognised. Most people with it feel nothing. Their liver is accumulating fat, and potentially progressing through inflammation to scarring, while they go about their daily lives entirely unaware.
The encouraging truth is that early MASLD is highly responsive to lifestyle change. A 5–10% reduction in body weight, a shift toward a Mediterranean dietary pattern, regular physical activity, and reduced sugar and processed food intake can reduce liver fat, dampen inflammation, and reverse early fibrosis. These are not small effects. They are among the most powerful interventions in hepatology.
If you have known risk factors — obesity, type 2 diabetes, metabolic syndrome, or a routine blood test showing elevated liver enzymes — raising fatty liver disease with your GP is worth doing. Early identification changes outcomes. And the conversation is worth having.
This article is health education, not medical advice. It is intended to help you understand MASLD and the evidence around it — not to replace clinical advice from your own doctor. If you are concerned about your liver health or any of the risk factors discussed here, that is a conversation for you to have with your GP or healthcare professional.