Fatty Liver Disease (MASLD): The Condition 1 in 4 Adults Have — and the New Drugs That Treat It

There’s a good chance you, or someone close to you, has a disease you’ve never been screened for. Fatty liver disease affects roughly one in four adults worldwide, the large majority are undiagnosed, and the routine “liver panel” most people assume would catch it often doesn’t. It’s one of the most common chronic conditions in the world and simultaneously one of the most overlooked.

That’s beginning to change, for two reasons. First, the field renamed the disease in 2023 to describe what actually causes it. Second — and more importantly for patients — the treatment landscape just transformed, going from zero approved drugs to two in under two years. This is a genuinely useful moment to understand what fatty liver is, why it matters far beyond the liver, and what can now be done about it.

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The New Name, and Why It Matters

In 2023, a large international consensus of liver societies formally retired the old terminology. NAFLD (non-alcoholic fatty liver disease) became MASLD (metabolic dysfunction-associated steatotic liver disease). Its more advanced, inflammatory form — NASH (non-alcoholic steatohepatitis) — became MASH (metabolic dysfunction-associated steatohepatitis).

In plain terms: MASLD is the umbrella condition — fat in the liver tied to metabolic dysfunction. MASH is the more serious version of MASLD, where that fat is now causing inflammation and cell damage. NAFLD and NASH are simply the old names for the same two things. The rest of this article uses the current terms, MASLD and MASH.

This is more than relabeling. The old name defined the disease by what it wasn’t — “non-alcoholic” — which was both stigmatizing and uninformative. The new name defines it by what it is: a liver condition driven by metabolic dysfunction. Under the updated definition, MASLD requires fat in the liver plus at least one cardiometabolic risk factor — things like overweight or obesity, elevated blood sugar or type 2 diabetes, high blood pressure, or abnormal cholesterol or triglyceridestriglycerides The main form of fat carried in the blood and stored in fat tissue. High levels travel with insulin resistance and cardiovascular risk, and they respond strongly to diet, alcohol, and omega-3 dose..

That definitional shift carries a clinical message: fatty liver is not a standalone liver quirk. It is the liver’s expression of the same metabolic dysfunction that drives diabetes and heart disease.

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A Metabolic Disease That Happens to Show Up in the Liver

This is the reframing that matters most. MASLD rarely travels alone. It clusters tightly with insulin resistance, type 2 diabetes, obesity, high triglycerides, and hypertension — the same cluster we discuss in our work on insulin resistance and HOMA-IR. In people with type 2 diabetes, fatty liver is extraordinarily common, and the two conditions worsen each other in a feedback loop.

The consequences extend well beyond the liver. People with MASLD are at elevated risk of cardiovascular disease — in fact, heart disease, not liver failure, is the leading cause of death in this population. This is why thinking of MASLD as “just a liver thing” is a mistake. It’s a flag for systemic metabolic trouble, and it belongs in the same risk conversation as cholesterol, blood pressure, and blood sugar.

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Why It’s So Often Missed

The reason fatty liver flies under the radar is that early disease is silent and the usual tests are imperfect.

There are typically no symptoms in the early stages — no pain, no jaundice, nothing a person would notice. And the liver enzyme most people associate with liver health, ALT, is frequently normal even in someone with significant fat or early scarring. A normal liver panel does not rule out MASLD.

Detection usually comes from a combination of tools: imaging that shows fat in the liver (a routine ultrasound often picks it up incidentally), simple calculated scores like FIB-4FIB-4 (Fibrosis-4 index) A simple calculated score — using age, AST, ALT, and platelet count — that estimates the probability of significant liver scarring without a biopsy. A score below 1.3 makes advanced fibrosis unlikely. that use ordinary blood values and age to estimate fibrosis risk, and specialized elastography (such as FibroScan) that measures liver stiffness as a proxy for scarring. The goal of all this isn’t just to find fat — it’s to find the people whose disease is progressing.

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The Spectrum: From Fat to Failure

MASLD is best understood as a spectrum rather than a single state. It begins as steatosissteatosis Abnormal fat accumulation inside an organ — most often the liver. — fat accumulation in liver cells. In a subset of people, this progresses to MASH, where the fat is accompanied by inflammation and liver-cell injury. Persistent MASH can drive fibrosis (scarring), which can advance through stages and, in some, culminate in cirrhosis and a meaningfully increased risk of liver cancer and liver failure.

Not everyone progresses, and progression is usually slow — often over years to decades. But because MASLD is so common, even a modest progression rate translates into a large and growing number of people with advanced liver disease. Fatty liver is now among the fastest-growing reasons for liver transplantation.

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The Treatment Revolution

For decades, the frustrating reality was that there was no approved drug for fatty liver. Clinicians could only recommend lifestyle change. That changed twice in quick succession.

Resmetirom (Rezdiffra) was approved by the FDA in March 2024 — the first drug ever approved specifically for MASH. It’s an oral, liver-directed thyroid hormone receptor-beta agonist, and in its pivotal phase 3 trial (MAESTRO-NASH) it produced significantly higher rates of MASH resolution and fibrosis improvement than placebo in patients with moderate fibrosis. Roughly a quarter to a third of treated patients achieved resolution of steatohepatitis, compared with about one in ten on placebo, with a parallel benefit on fibrosis.

Semaglutide (Wegovy) — the same GLP‑1GLP‑1 (glucagon-like peptide-1) A gut hormone released after eating that boosts insulin, slows the stomach, and signals fullness. Drugs like semaglutide mimic it. medication widely used for weight loss and type 2 diabetes — received FDA approval for MASH with fibrosis in August 2025, making it the second approved option. In its phase 3 trial (ESSENCE), nearly two-thirds of patients on semaglutide achieved resolution of steatohepatitis, versus about a third on placebo, with a significantly greater share also seeing fibrosis improve. This approval is a natural extension of what GLP‑1 drugs already do metabolically, and it directly connects fatty liver to the medications we cover throughout our GLP‑1 articles.

The arrival of these drugs is a real milestone. But two things keep it in perspective. Both are approved for specific populations — people with MASH and a defined degree of fibrosis, established through proper evaluation — not for anyone with a little fat on an ultrasound. And neither replaces the foundation.

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Lifestyle Is Still the Foundation

The single most effective intervention for fatty liver remains weight loss. Losing roughly 10% of body weight can resolve MASH and, in many people, improve fibrosis — an effect that rivals or exceeds what the drugs achieve, with broad metabolic benefits attached. More modest weight loss still reduces liver fat.

The supporting moves all target the underlying metabolic dysfunction: reducing added sugar (especially sugar-sweetened beverages and fructose), improving insulin sensitivity through regular exercise and resistance training, limiting alcohol, and managing the cardiometabolic conditions that travel with MASLD. The new medications work best layered on top of these changes, not in place of them.

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What to Actually Do

The practical takeaway is straightforward. If you have any of the conditions that travel with fatty liver — overweight or obesity, type 2 diabetes, prediabetes, metabolic syndromemetabolic syndrome A cluster of problems that tend to occur together — extra waist fat, high blood pressure, high blood sugar, high triglycerides, and low HDL. Having several at once sharply raises the risk of heart disease and type 2 diabetes., or abnormal cholesterol and triglycerides — assume you are at elevated risk and ask your clinician to evaluate your liver, rather than assuming a normal routine panel has cleared you. A basic assessment can include imaging and a simple fibrosis score, with elastography if risk appears elevated.

Catching MASLD early, while it’s still steatosis or early MASH, is the difference that matters, because that’s when it’s most reversible. The disease is common, quiet, and tied to the metabolic factors that shape long-term health — which is exactly why it deserves more attention than it gets.

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A note on a fast-moving field: MASLD/MASH treatment is evolving quickly, with additional drugs and combinations in late-stage trials. The two approvals discussed here are likely the beginning of a broader shift, and screening guidance for at-risk groups continues to develop — another reason to revisit this topic with your clinician rather than treating today’s picture as final.