GLP-1 for Fatty Liver Disease: ESSENCE Trial and MASH Approval

You probably have not thought much about your liver. Most people do not, until a routine lab comes back with elevated liver enzymes (ALT or AST). Then the question becomes urgent: What does this mean, and what do I do about it?

If you have received a diagnosis of NAFLD, MASLD, NASH, or MASH, you are far from alone. A 2023 systematic review estimated that about 30% of adults worldwide have fatty liver disease^[1]. Among people with obesity or type 2 diabetes, the rate is even higher. And for most people, the condition develops silently, without symptoms, until it appears on routine bloodwork or imaging.

The hopeful news is this: GLP-1 medications have been tested in randomized trials in people with MASH, with encouraging liver biopsy results. A phase 2 trial of tirzepatide was published in 2024 and a phase 3 trial of semaglutide in 2025, and in August 2025 the FDA granted accelerated approval to Wegovy (brand-name semaglutide) injection for MASH with moderate to advanced fibrosis^[4].

Here is what you need to know about the science, the trial data, and what it means if you are considering a GLP-1 medication.

What exactly is fatty liver disease and why does it happen?

Fatty liver disease is a spectrum. In 2023, liver societies renamed it: NAFLD became MASLD (metabolic dysfunction-associated steatotic liver disease), and NASH became MASH (metabolic dysfunction-associated steatohepatitis)^[5]. On one end, you have simple steatosis: fat accumulates in the liver, but there is no inflammation or cell damage. This is the most common form. On the other end, you have MASH (formerly NASH): inflammation and cell damage are present. The disease can progress further to fibrosis (scarring), cirrhosis, and eventually liver failure if untreated.

The connection to metabolism is direct. Fatty liver develops when the liver receives more fat than it can process. This happens through several mechanisms: excess calories are converted to fat and stored in the liver, high insulin levels drive fat synthesis in liver tissue, and metabolic dysfunction prevents the liver from clearing fat efficiently.

Weight gain and insulin resistance do not cause fatty liver in the traditional sense of a toxin causing damage. Rather, metabolic dysfunction creates an environment where fat accumulates faster than the body can clear it. This is why the condition is now called MASLD: it is fundamentally a metabolic problem, not a liver problem that happens to occur in people who are overweight.

The good news is that metabolic changes can help. GLP-1 medications may affect fatty liver through several pathways at once.

How GLP-1 medications affect liver health

Researchers are still working out exactly how GLP-1 medications improve the liver, and how much of the effect is direct versus a result of weight loss and better metabolic health.

The proposed mechanisms work on several levels.

Weight loss itself matters. Losing weight reduces the amount of fat being delivered to the liver, and in general, larger weight loss is linked with larger improvements in liver fat and inflammation. In the ESSENCE trial, people on semaglutide lost an average of 10.5% of body weight, compared with 2.0% on placebo^[2].

GLP-1 may reduce de novo lipogenesis. This is the process by which your body converts carbohydrates and other nutrients into new fat. Lower insulin levels and less incoming energy may mean the liver makes less fat from scratch.

GLP-1 improves insulin sensitivity. This is important because high insulin levels drive fat synthesis in the liver. By improving how your cells respond to insulin, GLP-1 medications may reduce the signal that tells your liver to make fat.

GLP-1 lowers blood sugar. In people with insulin resistance, the liver tends to release too much glucose. GLP-1 medications help bring blood sugar down, which may reduce metabolic stress on liver tissue.

These effects likely work together. Whether GLP-1 medications help the liver beyond what the same amount of weight loss would do on its own is still being studied.

The clinical trial evidence

Two randomized, placebo-controlled trials published in the New England Journal of Medicine looked at liver biopsies in adults with MASH and moderate to advanced fibrosis: a phase 3 trial of semaglutide and a phase 2 trial of tirzepatide.

The ESSENCE trial (semaglutide for MASH)

Published online in April 2025 in NEJM^[2]. This is the trial behind the FDA’s accelerated approval.

ESSENCE enrolled 1,197 adults with biopsy-confirmed MASH and stage F2-F3 fibrosis (moderate to advanced scarring), randomized 2 to 1 to semaglutide 2.4 mg weekly or placebo. The published results are a planned interim analysis of the first 800 participants at 72 weeks. The trial is planned to continue for 240 weeks to look at longer-term liver outcomes.

The results at 72 weeks^[2]:

• 62.9% of participants on semaglutide had resolution of steatohepatitis without worsening fibrosis (compared to 34.3% on placebo)
• 36.8% of participants on semaglutide had fibrosis improvement of at least one stage without worsening steatohepatitis (compared to 22.4% on placebo)
• Both primary endpoints were met
• Gastrointestinal side effects were more common with semaglutide

Fibrosis improvement is the important metric here. Resolving MASH is meaningful, but scarring is what drives the risk of cirrhosis and liver failure. Whether these biopsy improvements translate into fewer cases of cirrhosis, liver failure, or death is what the longer part of the trial is designed to show.

In August 2025, based on these results, the FDA granted accelerated approval to Wegovy (brand-name semaglutide) injection, together with a reduced-calorie diet and increased physical activity, for adults with noncirrhotic MASH and moderate to advanced liver fibrosis (consistent with stages F2 to F3)^[4]. Under accelerated approval, continued approval for this indication may depend on a confirmatory trial showing clinical benefit. The indication does not cover Wegovy tablets, people with cirrhosis, or compounded products.

The SYNERGY-NASH trial (tirzepatide for MASH)

Published in June 2024 in NEJM^[3]. This phase 2, dose-finding trial examined tirzepatide, a GIP and GLP-1 receptor agonist.

The study included 190 adults with biopsy-confirmed MASH and stage F2-F3 fibrosis. Participants received tirzepatide at doses of 5 mg, 10 mg, or 15 mg weekly, or placebo, for 52 weeks.

The results at 52 weeks^[3]:

• MASH resolution without worsening fibrosis: 44% at 5 mg, 56% at 10 mg, and 62% at 15 mg, compared to 10% on placebo
• Fibrosis improvement of at least one stage without worsening MASH: 55% at 5 mg, 51% at 10 mg, and 51% at 15 mg, compared to 30% on placebo
• The most common side effects were gastrointestinal, and most were mild or moderate

These are encouraging results, but the trial was small and short, and the authors called for larger and longer trials. Results from different trials, with different designs and lengths, cannot be compared directly. Tirzepatide is not FDA-approved for MASH.

Results vary. Trial results describe study participants and are not a prediction for any individual.

A critical distinction: branded approval vs. compounded medications

This is where you need to pay careful attention, because the regulatory landscape is specific and important for understanding your options.

In August 2025, the FDA granted accelerated approval to Wegovy (brand-name semaglutide) injection for MASH with moderate to advanced fibrosis, based on the ESSENCE trial data^[4]. When you see the headline “semaglutide works for fatty liver disease,” it refers to the branded product that went through FDA review.

Compounded semaglutide is a different product. It is not FDA-approved, and the FDA does not review compounded medications for safety, effectiveness, or quality. It is not the same as Wegovy, and it may differ in formulation, purity, and potency.

Compounded semaglutide contains the same molecule, but it has not been studied in MASH trials, so there is no trial evidence on whether it produces the liver results seen in ESSENCE. Weight loss from any cause can reduce liver fat. That is not the same as evidence for compounded semaglutide as a liver treatment, and it does not carry an FDA-approved indication for MASH.

If you have been diagnosed with MASH or advanced fibrosis and you are specifically seeking treatment for liver disease, ask the provider you choose to discuss all your options, including whether the brand-name product with FDA approval for this indication is appropriate for your situation.

If you are using compounded semaglutide primarily for weight management and you happen to have fatty liver disease or elevated liver enzymes, those markers may change as your weight changes, but that has not been studied for compounded products. This is different from taking a medication approved specifically for liver disease treatment.

Side effects and safety

GLP-1 medications have real side effects. In both MASH trials, gastrointestinal effects such as nausea, diarrhea, vomiting, and constipation were the most common^[2][3]. The Wegovy label includes a boxed warning about thyroid C-cell tumors seen in rodents, and warnings that include acute pancreatitis, acute gallbladder disease, and hypoglycemia when used with insulin or medications that stimulate insulin release^[4]. A licensed provider can review whether these risks apply to you.

Who this matters for

You should think about your liver health if any of these apply to you:

• You have been diagnosed with NAFLD, MASLD, NASH, or MASH
• You have elevated liver enzymes (ALT or AST) on recent lab work
• You have metabolic syndrome, type 2 diabetes, or obesity
• You have not had liver function tests in over a year and you have risk factors for fatty liver

Fatty liver is extremely common among people who are overweight or have metabolic dysfunction. Many people have undiagnosed fatty liver disease. If you have risk factors, it is worth asking a licensed provider about testing.

Programs differ in what they check before prescribing. Some order baseline labs, including liver function tests (ALT, AST, bilirubin, albumin); others ask for recent results from your primary care provider. Ask how the program handles labs and who reviews them. If your liver enzymes are elevated, the prescriber should review your results in the context of your full health history.

The path forward: what to discuss with your provider

If you are considering a GLP-1 medication, here are the conversations to have:

1. Get a baseline liver assessment. If you do not have recent lab work, ask about ALT, AST, and other liver function tests. If imaging has shown steatosis or fibrosis, bring those results to your provider discussion.

2. Understand your GLP-1 options. Ask the provider you choose to explain the difference between brand-name products with FDA approvals (such as Wegovy injection, approved for MASH) and compounded options. Ask which is appropriate for your specific situation based on your health history and diagnosis.

3. Plan for monitoring. Ask whether and when follow-up liver tests will be done, and who orders and reviews them.

4. Combine medication with lifestyle. The MASH indication for Wegovy is for use together with a reduced-calorie diet and increased physical activity^[4]. Ask what nutrition and activity support a program includes, if any.

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What the evidence means for your decision

The clinical trial data is encouraging. In randomized trials, semaglutide and tirzepatide improved MASH and fibrosis on liver biopsy more often than placebo. Longer trials are still needed to show whether those improvements prevent cirrhosis and other liver outcomes.

The FDA’s accelerated approval of Wegovy for MASH means one GLP-1 medication now has a labeled liver indication, not only a weight-management indication. If you have MASH with moderate to advanced fibrosis, ask the provider you choose whether this option fits your situation.

At the same time, if you are using compounded semaglutide for weight management and you have fatty liver disease, keep in mind that compounded products have not been studied for MASH and do not carry an FDA-approved indication.

The key is getting baseline labs, understanding your diagnosis, and having an honest conversation with a licensed provider about which option makes sense for your situation.

Citations

[1] Younossi ZM et al. “The global epidemiology of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH): a systematic review.” Hepatology. 2023;77(4):1335-1347. https://pubmed.ncbi.nlm.nih.gov/36626630/

[2] Sanyal AJ et al. “Phase 3 Trial of Semaglutide in Metabolic Dysfunction-Associated Steatohepatitis.” New England Journal of Medicine. 2025;392(21):2089-2099. https://pubmed.ncbi.nlm.nih.gov/40305708/

[3] Loomba R et al. “Tirzepatide for Metabolic Dysfunction-Associated Steatohepatitis with Liver Fibrosis.” New England Journal of Medicine. 2024;391(4):299-310. https://pubmed.ncbi.nlm.nih.gov/38856224/

[4] Novo Nordisk. Wegovy (semaglutide) prescribing information. US Food and Drug Administration. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/215256s025lbl.pdf

[5] Rinella ME et al. “A multisociety Delphi consensus statement on new fatty liver disease nomenclature.” Hepatology. 2023;78(6):1966-1986. https://pubmed.ncbi.nlm.nih.gov/37363821/