Fatty Liver Disease (MASLD): Symptoms, Causes, Tests and Treatment

Fatty liver disease means that too much fat has built up inside the liver. Its most common form is now called MASLD (metabolic dysfunction-associated steatotic liver disease), the new name for what used to be NAFLD. It is linked to excess weight, type 2 diabetes and other metabolic problems, and it is usually silent for years. In some people, fat triggers inflammation (MASH, formerly NASH) that slowly scars the liver.

The reassuring part: fatty liver can improve. Losing 5% to 10% of your body weight, moving more and cutting back on sugary drinks and alcohol can reduce liver fat, calm inflammation and even reverse some scarring. Since 2024, people with MASH and significant scarring also have FDA-approved medicines.

Key takeaways

• About 30% of adults worldwide have fatty liver disease, and up to 75% of US adults with overweight.
• Most people feel nothing. Swelling of the legs or belly, yellow skin or confusion suggest advanced disease.
• Normal liver enzymes do not rule it out. What matters is scarring (fibrosis), checked with the FIB-4 score, then FibroScan or the ELF blood test.
• Weight loss is the core treatment: 3% to 5% reduces liver fat, 7% to 10% or more is needed to improve inflammation and fibrosis.
• Resmetirom (Rezdiffra, March 2024) and semaglutide (Wegovy, August 2025) are approved for adults with MASH and moderate to advanced fibrosis without cirrhosis.

What is fatty liver disease?

Hepatic steatosis is the medical term for excess fat in the liver. Because it has many causes, experts now group them under one term: steatotic liver disease.

From NAFLD to MASLD: the new names explained

In 2023, three international liver societies ran a consensus process with 236 experts and patient advocates from 56 countries, many of whom found the terms "nonalcoholic" and "fatty" stigmatizing. The new names are:

• MASLD replaces NAFLD: fat in the liver plus at least one of five cardiometabolic risk factors.
• MASH (metabolic dysfunction-associated steatohepatitis) replaces NASH: the inflammatory form, with injured liver cells.
• MetALD: MASLD plus higher alcohol intake, 140 to 350 grams a week for women and 210 to 420 grams for men.
• Cryptogenic steatotic liver disease: liver fat with no metabolic risk factor and no known cause.

The disease itself has not changed, so studies run under the old names still apply.

How common is it?

A 2023 meta-analysis of 92 studies and more than 9.3 million people found a global prevalence of about 30% (31.2% in North America), rising from 25% in 1990-2006 to 38% in 2016-2019. The NIDDK estimates that about 24% of US adults have the condition. It affects up to 75% of people with overweight, more than 90% of people with severe obesity and one-third to two-thirds of people with type 2 diabetes.

Causes and risk factors of fatty liver

The main risk factors listed by the NIDDK are:

• overweight or obesity, especially fat around the waist;
• insulin resistance, prediabetes or type 2 diabetes;
• abnormal blood fats, including high triglycerides and low HDL cholesterol;
• metabolic syndrome and high blood pressure;
• genes: certain gene variants make fatty liver more likely and may help explain higher rates in some ethnic groups.

Other causes of liver fat must be ruled out: alcohol, rapid weight loss or malnutrition, medicines such as corticosteroids and estrogens, toxins and rare genetic diseases such as Wilson disease. In children, sleep apnea is among the listed risk factors.

The five cardiometabolic criteria of MASLD

Liver fat counts as MASLD with at least one of these (adult criteria, Merck Manual):

• body mass index above 25 kg/m² (above 23 in people of Asian descent), or a waist above 94 cm (37 inches) in men or 80 cm (31.5 inches) in women;
• fasting glucose above 100 mg/dL (5.6 mmol/L), A1C above 5.7%, type 2 diabetes or diabetes treatment;
• blood pressure above 130/85 mm Hg or blood pressure treatment;
• triglycerides above 150 mg/dL (1.7 mmol/L) or lipid-lowering treatment;
• HDL cholesterol below 40 mg/dL (1.0 mmol/L) in men or 50 mg/dL (1.3 mmol/L) in women, or lipid-lowering treatment.

Alcohol and MetALD

The American Association for the Study of Liver Diseases (AASLD) notes that even moderate drinking raises the risk of advanced fibrosis in MASLD, and no safe limit has been set. Heavy drinking (40 g a day or more for women, 60 g for men) should be avoided. Our article on how much alcohol is too much explains what recent research shows.

Fatty liver symptoms

MASLD is usually silent. According to the NIDDK, you may feel tired or notice discomfort in the upper right side of your belly. The liver is enlarged in about 75% of people with MASH (Merck Manual). Many people learn about it from a routine blood test or ultrasound.

Signs of advanced disease (cirrhosis)

Cirrhosis can be silent at first. The NIDDK lists these warning signs:

• swelling in the lower legs, ankles or feet (edema) and swelling of the belly from fluid (ascites);
• yellow skin or whites of the eyes (jaundice) and itching;
• confusion, memory problems, personality changes or sleep problems;
• easy bruising, bleeding, or vomiting blood from enlarged veins (varices);

Fatty liver symptoms in women

Symptoms are the same in women and men, but some risk factors differ. A 2025 meta-analysis of 24 studies in East Asia found that women with PCOS and fatty liver had more belly fat, more insulin resistance and higher testosterone, and its authors suggest early screening in this group.

How is fatty liver disease diagnosed?

Doctors check for liver fat, rule out other causes and, above all, measure scarring, which predicts the future of the liver.

Blood tests

A liver panel measures enzymes such as ALT, AST and GGT, plus bilirubin and albumin. In MASLD, ALT is often mildly raised, but the AASLD stresses that enzymes are often normal even in advanced disease and should never be used alone to rule it out. The guidance considers ALT above 30 U/L abnormal and cites normal upper limits of 29 to 33 U/L for men and 19 to 25 U/L for women. Tests for hepatitis B and C and ferritin help rule out other causes. Our deep dive on the fatty liver blood test explains what each marker can and cannot show.

The FIB-4 score

FIB-4 turns four routine values into a fibrosis estimate: age multiplied by AST, divided by the platelet count multiplied by the square root of ALT. The AASLD recommends it as the first step for anyone with MASLD. Below 1.3 means low risk: stay in primary care and repeat it every one to two years if you have diabetes or several risk factors. A score of 1.3 or higher calls for a second test, and above 2.67 is a reason to consider referral to a liver specialist. Because FIB-4 rises with age, a cutoff of 2.0 is used after 65, and it is less accurate under 35. Compare scores in our article on GGT vs FIB-4 for liver fibrosis.

Imaging: ultrasound, FibroScan and MRI

Ultrasound can show fat in the liver, but it does not measure scarring. Vibration-controlled transient elastography (VCTE, often called FibroScan) measures liver stiffness in a quick, painless exam. Magnetic resonance elastography (MRE) is an MRI-based alternative. The ELF (Enhanced Liver Fibrosis) blood test is the AASLD's other preferred second test. European guidelines (2024) use the same steps: a blood score, then imaging. Biopsy is kept for unclear cases.

Fatty liver test thresholds at a glance

Main cutoffs from US guidelines (AASLD, NASPGHAN); your doctor may use slightly different values.

How to read your results

Read the whole picture. A raised ALT with a FIB-4 below 1.3 usually means fat without significant scarring: lifestyle change and follow-up. Doctors also look at the AST to ALT ratio, which is read differently depending on the suspected cause. A low platelet count, low albumin or high bilirubin may signal cirrhosis and needs a prompt visit. Prediabetes-range A1C, high triglycerides or low HDL are drivers of the disease and targets of treatment.

Fatty liver treatment

Weight loss: the 5% and 10% targets

According to the NIDDK, losing at least 3% to 5% of your body weight can reduce liver fat, and you may need to lose 7% to 10% to reduce inflammation and fibrosis. In a landmark study of 293 people with biopsy-proven NASH, 58% of those who lost at least 5% of their weight saw their NASH resolve. Among those who lost 10% or more, 90% had NASH resolution and 45% saw their fibrosis regress. For someone weighing 220 pounds (100 kg), 5% is 11 pounds. Go gradually: rapid weight loss can make liver disease worse.

Physical activity

According to the NIDDK, physical activity helps even without weight loss, and the AASLD strongly encourages people with MASLD to be as active as they can.

Medicines approved for MASH

• Resmetirom (Rezdiffra): FDA accelerated approval on March 14, 2024, for adults with noncirrhotic MASH and moderate to advanced scarring, with diet and exercise. A daily pill that activates the thyroid hormone receptor beta in the liver (ChEMBL: thyroid hormone receptor beta-1 agonist). Diarrhea and nausea are the most common side effects; it interacts with some statins.
• Semaglutide (Wegovy): FDA accelerated approval in August 2025 for the same group, with a reduced-calorie diet and more activity. A weekly injection that mimics the gut hormone GLP-1 (ChEMBL: GLP-1 receptor agonist). Nausea, diarrhea, vomiting and constipation are common.

Accelerated approval rests on improved liver biopsies; longer studies must confirm fewer cirrhosis cases and deaths. Both are approved only for people without cirrhosis. The AASLD also describes off-label options: pioglitazone (a diabetes pill acting on PPAR-gamma, ChEMBL), which improves liver tissue but causes weight gain, and vitamin E 800 IU a day, with no proven effect on fibrosis. Do not start supplements on your own: some herbal remedies damage the liver.

Treating the conditions that drive fatty liver

Treating diabetes, blood pressure and cholesterol protects the liver and the heart. The AASLD states that statins are safe in MASLD, including advanced disease. Bariatric surgery often resolves MASLD or MASH in eligible people without cirrhosis. People with MASH cirrhosis need regular screening for liver cancer and enlarged veins, and a transplant is an option if the liver fails.

Fatty liver diet: what to eat and what to limit

The AASLD recommends diets low in refined carbohydrates and saturated fat and rich in fiber and unsaturated fats, such as the Mediterranean diet, with a modest calorie deficit if you have excess weight. The NIDDK advises to:

• favor most fruits, vegetables and whole grains;
• replace saturated and trans fats with unsaturated fats, especially omega-3s;
• limit simple sugars, especially fructose from soft drinks, sports drinks, sweetened tea and juices;
• minimize alcohol and watch portion sizes.

Based on population studies, the AASLD says three or more cups of coffee a day could be recommended if you have no reason to avoid it. Timing may matter too: see our articles on a prediabetes diet and liver fat and on late-night eating and fatty liver. These same habits are also the best prevention.

Fatty liver in children and teens

MASLD has become the most common liver disease in children. According to the NIDDK, close to 10% of US children aged 2 to 19 have it. The pediatric guideline (NASPGHAN) recommends considering an ALT blood test from ages 9 to 11 in children with obesity, and in children with overweight who have risk factors such as belly fat, insulin resistance, sleep apnea or a family history. It uses limits of 26 U/L for boys and 22 U/L for girls and advises against ultrasound for screening. Treatment relies on lifestyle change, and the guideline recommends avoiding sugar-sweetened beverages.

Prognosis: is fatty liver dangerous?

According to the Merck Manual, simple steatosis progresses to MASH in 12% to 40% of people, and about 10% of people with MASLD develop cirrhosis over 20 years. The stage of fibrosis is what shapes the outlook: a 2020 meta-analysis of 13 studies and 4,428 patients found that, compared with no fibrosis, people with cirrhosis had a 3.4 times higher risk of death from any cause and an 11 times higher risk of liver-related death.

Without advanced fibrosis, heart disease and cancers outside the liver are the most common causes of death, so treating fatty liver also protects your heart.

When to see a doctor

Make an appointment with your primary care clinician if:

• a blood test shows a raised ALT, AST or GGT, or an ultrasound mentions a fatty liver;
• you have type 2 diabetes or obesity and have never had your liver risk assessed;
• your FIB-4 is 1.3 or higher, or a parent or sibling has cirrhosis.

Seek care promptly if you notice yellow skin or eyes, a swollen belly, swelling of the legs or dark urine. Call 911 or go to the emergency room if you vomit blood, pass black or bloody stools, or become confused or very drowsy: these can be signs of bleeding varices or liver failure.

Latest scientific advances in fatty liver disease

A new, less stigmatizing name (2023)

The 2023 multisociety consensus replaced NAFLD and NASH with MASLD and MASH and created the MetALD category for people with both metabolic risk and higher alcohol intake. The 2024 European guidelines (EASL-EASD-EASO) adopted it and recommend FIB-4 followed by elastography in people with cardiometabolic risk factors.

Resmetirom, the first MASH drug (2024)

In the MAESTRO-NASH phase 3 trial (NCT03900429), 966 adults with biopsy-proven NASH and moderate to advanced fibrosis took resmetirom 80 mg, 100 mg or placebo. After 52 weeks, NASH resolved in 25.9% and 29.9% of the treated groups versus 9.7% with placebo, and fibrosis improved by at least one stage in 24.2% and 25.9% versus 14.2%. The trial continues to 54 months to check hard outcomes.

Semaglutide approved for MASH (2025)

In the ESSENCE phase 3 trial (NCT04822181), the first 800 of 1,197 people with MASH and stage 2 or 3 fibrosis received weekly semaglutide 2.4 mg or placebo for 72 weeks. MASH resolved in 62.9% versus 34.3%, and fibrosis improved in 36.8% versus 22.4%. Participants lost 10.5% of their body weight versus 2.0%. It runs for 240 weeks to look at liver events.

The next wave: dual agonists and FGF21 drugs

Tirzepatide, which acts on both GIP and GLP-1 receptors (ChEMBL), resolved MASH in 44% to 62% of participants versus 10% with placebo in the phase 2 SYNERGY-NASH trial (NCT04166773, NEJM 2024). Efruxifermin, a long-acting analogue of the hormone FGF21, is being tested even in cirrhosis: in the phase 2b SYMMETRY trial (NCT05039450), it did not beat placebo at 36 weeks, but at 96 weeks fibrosis improved in 29% of patients on 50 mg versus 11% on placebo. Phase 3 trials are recruiting for efruxifermin (NCT06215716, NCT06528314), survodutide, a glucagon and GLP-1 dual agonist (NCT06632444), pegozafermin (NCT06318169), and tirzepatide and retatrutide in 4,500 people (NCT07165028).

Cirrhosis trials move toward hard outcomes (2026)

A 2026 review in Drugs explains that phase 3 trials in compensated MASH cirrhosis now measure what matters to patients: fluid buildup, bleeding varices, liver failure, transplant and death, and enroll patients with noninvasive tests rather than biopsy.

Which tests can help?

The most useful results to bring to your doctor are:

• liver enzymes ALT, AST and GGT, plus alkaline phosphatase, bilirubin and albumin;
• a complete blood count, for the platelet count used in FIB-4;
• fasting glucose and A1C, to detect prediabetes or diabetes;
• a lipid panel (triglycerides, HDL and LDL cholesterol);
• ferritin and hepatitis B and C tests, to rule out other liver diseases;

From your age, AST, ALT and platelets, your clinician can calculate FIB-4 in seconds.

Glossary

• Hepatic steatosis: buildup of fat in liver cells, the medical name for fatty liver.
• MASH: metabolic dysfunction-associated steatohepatitis, the inflammatory form, formerly NASH.
• MetALD: MASLD with higher alcohol intake (140 to 350 g a week for women, 210 to 420 g for men).
• Fibrosis: scar tissue in the liver, staged from F0 (none) to F4 (cirrhosis).
• FIB-4: a score from age, AST, ALT and platelets that estimates the risk of advanced fibrosis.
• VCTE (FibroScan): an ultrasound-based exam that measures liver stiffness in kilopascals (kPa).
• ELF test: Enhanced Liver Fibrosis test, a blood test that estimates the risk of liver scarring.

Frequently asked questions

What are the symptoms and causes of hepatic steatosis?

It usually causes no symptoms, sometimes tiredness or discomfort under the right ribs. The most common cause is metabolic: excess weight, insulin resistance, diabetes, high triglycerides and high blood pressure. Alcohol and some medicines can also cause it.

Can fatty liver disease cause edema?

Not in its early stages. Swelling of the legs, ankles or feet (edema) and fluid in the belly (ascites) appear when fatty liver has progressed to cirrhosis and the liver no longer works well. New swelling needs a prompt medical visit.

What are the best foods for liver health?

A Mediterranean-style diet: vegetables, fruits, legumes, whole grains, olive oil, nuts and fish. Coffee, three or more cups a day, is associated with liver benefits. Limit sugary drinks, saturated fat and alcohol.

What is the life expectancy with fatty liver disease?

For people with fatty liver and no advanced fibrosis, the AASLD notes that heart disease and cancers outside the liver are the main causes of death, not the liver. With cirrhosis, the risk of liver-related death is about 11 times higher than with no fibrosis, which is why fibrosis is measured.

Can you die from fatty liver disease?

Yes, but it is uncommon and usually takes many years. Liver deaths come from cirrhosis or liver cancer. According to the NIDDK, the most common cause of death in people with fatty liver is cardiovascular disease.

What is the best medication for fatty liver?

There is no pill for simple fatty liver: weight loss and exercise come first. For adults with MASH and moderate to advanced fibrosis without cirrhosis, the FDA has approved resmetirom (Rezdiffra) and semaglutide (Wegovy).

Is fatty liver reversible?

Often, yes. Liver fat can fall with a 3% to 5% weight loss, and with a loss of 10% or more, most people in one study saw their MASH resolve and almost half saw fibrosis regress.

Sources

• Rinella ME et al. — A multisociety Delphi consensus statement on new fatty liver disease nomenclature — Hepatology, 2023 — doi.org
• Rinella ME et al. — AASLD Practice Guidance on the clinical assessment and management of nonalcoholic fatty liver disease — Hepatology, 2023 — pmc.ncbi.nlm.nih.gov
• European Association for the Study of the Liver, EASD, EASO — EASL-EASD-EASO Clinical Practice Guidelines on the management of MASLD — J Hepatol, 2024 — doi.org
• Younossi ZM et al. — The global epidemiology of NAFLD and NASH: a systematic review — Hepatology, 2023 — doi.org
• Vilar-Gomez E et al. — Weight Loss Through Lifestyle Modification Significantly Reduces Features of Nonalcoholic Steatohepatitis — Gastroenterology, 2015 — doi.org
• Taylor RS et al. — Association Between Fibrosis Stage and Outcomes of Patients With NAFLD: A Systematic Review and Meta-Analysis — Gastroenterology, 2020 — doi.org
• Sterling RK et al. — Development of a simple noninvasive index to predict significant fibrosis (FIB-4) — Hepatology, 2006 — doi.org
• Vos MB et al. — NASPGHAN Clinical Practice Guideline for the Diagnosis and Treatment of NAFLD in Children — J Pediatr Gastroenterol Nutr, 2017 — pmc.ncbi.nlm.nih.gov
• Harrison SA et al. — A Phase 3, Randomized, Controlled Trial of Resmetirom in NASH with Liver Fibrosis — N Engl J Med, 2024 — doi.org
• Sanyal AJ et al. — Phase 3 Trial of Semaglutide in Metabolic Dysfunction-Associated Steatohepatitis — N Engl J Med, 2025 — doi.org
• Loomba R et al. — Tirzepatide for Metabolic Dysfunction-Associated Steatohepatitis with Liver Fibrosis — N Engl J Med, 2024 — doi.org
• Noureddin M et al. — Efruxifermin in Compensated Liver Cirrhosis Caused by MASH — N Engl J Med, 2025 — doi.org
• Patil R et al. — MASH-Cirrhosis Clinical Trials: Lessons Learned and Future Directions — Drugs, 2026 — doi.org
• Wu Z et al. — Risk Factors for MASLD in Patients With Polycystic Ovary Syndrome in East Asia: A Review and Meta-Analysis — Endocr Pract, 2025 — doi.org
• National Institute of Diabetes and Digestive and Kidney Diseases — Definition and Facts of NAFLD and NASH — NIDDK — niddk.nih.gov
• National Institute of Diabetes and Digestive and Kidney Diseases — Symptoms and Causes of NAFLD and NASH — NIDDK — niddk.nih.gov
• National Institute of Diabetes and Digestive and Kidney Diseases — Treatment of NAFLD and NASH — NIDDK — niddk.nih.gov
• National Institute of Diabetes and Digestive and Kidney Diseases — Eating, Diet and Nutrition for NAFLD and NASH — NIDDK — niddk.nih.gov
• National Institute of Diabetes and Digestive and Kidney Diseases — Symptoms and Causes of Cirrhosis — NIDDK — niddk.nih.gov
• US Food and Drug Administration — FDA Approves First Treatment for Patients with Liver Scarring Due to Fatty Liver Disease — FDA, 2024 — fda.gov
• US Food and Drug Administration — FDA approves treatment for serious liver disease known as MASH — FDA, 2025 — fda.gov
• Merck Manual Professional Version — Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) — Merck Manuals — merckmanuals.com
• Madrigal Pharmaceuticals — MAESTRO-NASH: Phase 3 Study of Resmetirom in Patients With NASH and Fibrosis (NCT03900429) — ClinicalTrials.gov — clinicaltrials.gov

Further reading

• How to lower ALT levels: 8 practical steps
• High ALT: causes, levels and when to worry
• Alkaline phosphatase (ALP) test explained
• Hepatitis blood test: what results mean
• Liver cancer prognosis: what shapes survival
• Insulin resistance without obesity: the tests
• Type 2 diabetes remission: diet and exercise trial

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