A new era in fatty liver and obesity
For years, the only proven treatment for metabolic (fatty) liver disease was weight loss through diet and exercise, effective, but hard to sustain. A class of injectable medicines has changed that conversation. GLP-1 receptor agonists such as semaglutide, and the dual GLP-1/GIP receptor agonist tirzepatide, produce weight loss on a scale not previously possible with medication, and the evidence now shows they can improve the liver disease itself.
How they work
GLP-1 and GIP are natural gut hormones released when we eat. These drugs mimic them: they slow stomach emptying, reduce appetite and signal fullness to the brain, and improve the body’s handling of sugar and insulin. The result is that people eat less, lose substantial weight, and improve their metabolic health, and because fatty liver disease (MASLD/MASH) is driven by exactly this metabolic dysfunction, the liver benefits as the weight and insulin resistance come down. They are given as a once-weekly injection under the skin, with the dose stepped up gradually to limit side effects.
What the evidence shows
The weight-loss effect is large. In the pivotal obesity trials, semaglutide 2.4 mg weekly produced average weight loss of around 15% of body weight at 68 weeks (STEP 1), and tirzepatide at its highest studied dose produced average weight loss of around 21% at 72 weeks (SURMOUNT-1), figures well beyond what older weight-loss medications achieved.
More importantly for the liver, two major trials have tested these drugs directly against liver biopsy in patients with MASH and significant fibrosis:
- Semaglutide (ESSENCE trial, New England Journal of Medicine, 2025): in patients with MASH and moderate-to-advanced fibrosis, resolution of the steatohepatitis without worsening of fibrosis occurred in 62.9% on semaglutide versus 34.3% on placebo, and fibrosis improved without worsening of MASH in 36.8% versus 22.4%. Average weight loss was about 10.5% versus 2.0%.
- Tirzepatide (SYNERGY-NASH trial, New England Journal of Medicine, 2024): in a phase 2 study, MASH resolved without worsening fibrosis in up to 62% of patients on the highest dose versus 10% on placebo.
The main side effects are gastrointestinal, nausea, reduced appetite, occasionally vomiting or diarrhoea, usually mild, most noticeable when the dose is increased, and lessened by going up slowly.
Who they suit
These medicines are considered for people with obesity or type 2 diabetes and metabolic (fatty) liver disease, particularly those with MASH and fibrosis who have not achieved enough with lifestyle change alone. They are not for everyone, they are avoided in certain conditions and in pregnancy, and they work best as part of a broader plan, not a standalone fix. Weight regain is common if the drug is stopped, so they are best seen as long-term metabolic treatment. As of now, semaglutide and tirzepatide are approved for obesity and type 2 diabetes; their use specifically for MASH is guided by the emerging trial evidence above, and regulatory approval status for the liver indication should be confirmed at the time of prescribing.
Dr Kalal’s role
As a hepatologist managing fatty liver disease, Dr Kalal assesses whether one of these agents is appropriate for you, weighs it against your liver fibrosis stage, diabetes and other conditions, prescribes and titrates the dose, and monitors both your weight and your liver response over time, using tools such as FibroScan and blood tests to track progress. The medicine is one lever; sustained results come from combining it with nutrition, activity and follow-up.