Key points
- Non-alcoholic fatty liver disease (NAFLD) affects approximately 1 in 3 adults in the UK
- Semaglutide has been shown to reduce liver fat by 50 to 60 per cent and resolve NASH in up to 59 per cent of patients in clinical trials
- GLP-1 medications are not yet licensed specifically for liver disease but trials for this indication are ongoing
- Weight loss of 7 to 10 per cent is typically needed to improve NASH, which GLP-1 therapies reliably achieve
- The renamed condition MASLD (metabolic dysfunction-associated steatotic liver disease) reflects its link to metabolic health
Understanding fatty liver disease
Non-alcoholic fatty liver disease (NAFLD) is a spectrum of conditions characterised by the accumulation of excess fat in the liver in people who drink little or no alcohol. It is the most common chronic liver disease worldwide and is strongly associated with obesity, type 2 diabetes and metabolic syndrome.
In 2023, the international hepatology community renamed NAFLD to MASLD (metabolic dysfunction-associated steatotic liver disease) to better reflect its metabolic origins. Both terms are currently used in clinical practice and the medical literature.
The NAFLD spectrum
- Simple steatosis (fatty liver): Fat accumulation without significant inflammation. Generally considered benign but can progress.
- NASH (non-alcoholic steatohepatitis): Fat accumulation with liver inflammation and hepatocyte damage (ballooning). This is the stage at which liver damage occurs and fibrosis can develop.
- Fibrosis: Scarring of liver tissue resulting from chronic inflammation. Staged F0 (none) to F4 (cirrhosis).
- Cirrhosis: Advanced scarring that impairs liver function. Can lead to liver failure and hepatocellular carcinoma.
The UK burden
According to the British Liver Trust, NAFLD affects approximately one in three adults in the United Kingdom. Among those with obesity, the prevalence rises to an estimated 70 to 80 per cent. Of those with NAFLD, approximately 20 per cent will develop NASH, and of those with NASH, a proportion will progress to fibrosis and cirrhosis.
Liver disease is the third leading cause of premature death in the UK, and the only one of the top five causes that continues to rise. Most cases of liver disease in the UK are attributable to alcohol, obesity or viral hepatitis, and the obesity-related component is growing rapidly.
Terminology update: You may see the terms NAFLD/NASH being replaced with MASLD/MASH in newer publications. This reflects an international consensus to use terminology that is more accurate and less stigmatising. The underlying conditions are the same.
Why weight loss helps the liver
Weight loss is currently the most effective treatment for NAFLD and NASH. Research has established clear thresholds:
- 3 to 5 per cent weight loss: Reduces liver steatosis (fat content)
- 7 to 10 per cent weight loss: Can resolve NASH (inflammation and ballooning)
- 10 per cent or more weight loss: Can improve or even reverse fibrosis
The challenge has always been that achieving and maintaining this degree of weight loss through lifestyle changes alone is extremely difficult. Fewer than 10 per cent of patients with NASH achieve 10 per cent weight loss through diet and exercise alone. This is where GLP-1 medications have transformed the treatment landscape.
Semaglutide and liver disease: the evidence
The STEP-NASH trial (semaglutide 2.4 mg)
The STEP-NASH trial was a phase 2b randomised controlled trial published in the New England Journal of Medicine that evaluated semaglutide 2.4 mg (the Wegovy dose) in patients with biopsy-confirmed NASH and fibrosis stages F2 or F3 (moderate to advanced fibrosis).
Key findings after 72 weeks:
- NASH resolution: 59 per cent of patients on semaglutide achieved resolution of NASH without worsening of fibrosis, compared with 17 per cent on placebo
- Fibrosis improvement: 34 per cent of patients on semaglutide showed improvement in fibrosis stage by at least one grade
- Liver fat reduction: MRI-measured liver fat decreased by approximately 50 to 60 per cent
- Weight loss: Participants lost an average of approximately 13 per cent of body weight
Earlier trials
An earlier phase 2 trial published in the Lancet in 2021 evaluated semaglutide at daily subcutaneous doses of 0.1 mg, 0.2 mg and 0.4 mg in patients with NASH. After 72 weeks, NASH resolution was achieved in 40 per cent (0.1 mg), 36 per cent (0.2 mg) and 59 per cent (0.4 mg) of participants, compared with 17 per cent with placebo.
Note on licensing: Semaglutide is not currently approved by the MHRA for treating NAFLD or NASH. However, patients prescribed semaglutide for weight management or type 2 diabetes may experience liver benefits as an additional effect of treatment.
Tirzepatide and liver disease
Tirzepatide (Mounjaro), the dual GLP-1/GIP receptor agonist, has also shown significant hepatic benefits in clinical studies.
The SYNERGY-NASH trial evaluated tirzepatide in patients with biopsy-confirmed NASH. Preliminary results presented at international liver conferences showed:
- NASH resolution rates of up to 74 per cent at the highest dose
- Significant reductions in liver fat content on imaging
- Improvement in markers of liver inflammation (ALT, AST)
- Greater absolute weight loss than semaglutide, potentially offering more benefit for liver-related outcomes
Full peer-reviewed publication of the SYNERGY-NASH results is expected in 2026. If confirmed, these findings could strengthen the case for GLP-1-based therapies as a treatment for liver disease.
How GLP-1 medications help the liver
The liver benefits of GLP-1 medications appear to result from both weight-loss-dependent and weight-loss-independent mechanisms.
Weight-loss-dependent effects
- Reduced fatty acid delivery: Weight loss reduces the release of free fatty acids from adipose tissue, which are a major source of liver fat
- Reduced visceral fat: GLP-1 medications preferentially reduce visceral (abdominal) fat, which is the fat depot most closely linked to liver steatosis
- Improved insulin sensitivity: Better insulin sensitivity reduces de novo lipogenesis (the liver's own production of fat from carbohydrates)
Potential direct hepatic effects
- Reduced liver inflammation: GLP-1 agonists reduce pro-inflammatory cytokines including TNF-alpha and interleukin-6, which drive NASH progression
- Reduced oxidative stress: Preclinical studies suggest GLP-1 receptor activation reduces hepatic oxidative stress
- Anti-fibrotic effects: Some research suggests GLP-1 agonists may directly inhibit hepatic stellate cell activation, which is the key driver of liver fibrosis
- Improved lipid metabolism: Enhanced hepatic fatty acid oxidation and reduced triglyceride synthesis
Monitoring liver health on GLP-1 therapy
If you have been diagnosed with NAFLD or NASH and are taking a GLP-1 medication, your doctor may monitor your liver health through several methods.
Blood tests
- Liver enzymes (ALT, AST, GGT): Elevated levels indicate liver inflammation. GLP-1 therapy typically reduces ALT and AST levels within the first few months.
- FIB-4 index: A calculated score using age, ALT, AST and platelet count that estimates fibrosis severity. Useful for monitoring over time.
- Enhanced Liver Fibrosis (ELF) score: A blood test measuring three markers of fibrosis, used in some NHS centres.
Imaging
- FibroScan (transient elastography): A non-invasive ultrasound-based test that measures liver stiffness (correlating with fibrosis) and liver fat content (CAP score). Available in most NHS hepatology departments.
- MRI-PDFF: Magnetic resonance imaging proton density fat fraction is the most accurate non-invasive method for measuring liver fat. Used mainly in clinical trials and specialist centres.
Liver biopsy
Liver biopsy remains the gold standard for diagnosing and staging NASH but is invasive and not routinely performed for monitoring purposes. It is mainly used in clinical trials or when there is diagnostic uncertainty.
Current treatment landscape for NASH in the UK
As of April 2026, there is no medication specifically licensed by the MHRA for treating NAFLD or NASH. The current standard of care is:
- Lifestyle modification: Diet and exercise to achieve weight loss of 7 to 10 per cent
- Management of comorbidities: Treating diabetes, hypertension and dyslipidaemia
- Vitamin E: Recommended by NICE for non-diabetic adults with NASH (specialist-initiated only)
- Pioglitazone: May be considered in certain patients with NASH and diabetes
- Bariatric surgery: For patients with severe obesity and NASH who meet surgical criteria
The approval of resmetirom (Rezdiffra) by the FDA in 2024 for NASH with moderate fibrosis marked the first dedicated NASH therapy globally. MHRA approval for the UK is expected to be reviewed. GLP-1 agonists with specific NASH indications may follow pending trial results.
Important: If you have been diagnosed with fatty liver disease, do not start or stop any medication without consulting your GP or hepatologist. GLP-1 medications are currently prescribed for obesity and diabetes, not directly for liver disease, though liver benefits may be a valuable additional effect.
Practical advice for patients
If you have NAFLD or NASH and are considering or already taking a GLP-1 medication, the following steps can maximise liver benefits:
- Aim for at least 7 to 10 per cent weight loss, which is achievable with most GLP-1 therapies
- Follow a Mediterranean-style diet rich in vegetables, olive oil, fish and whole grains
- Limit added sugars and refined carbohydrates, which directly contribute to liver fat
- Avoid or minimise alcohol, even in NAFLD (any alcohol adds to liver burden)
- Engage in regular physical activity — both aerobic exercise and resistance training benefit liver health
- Attend regular monitoring appointments and blood tests as advised by your doctor