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

Fatty liver disease means too much fat has built up in the liver. A healthy liver contains a small amount of fat. When fat makes up more than about 5% of the liver’s weight, the condition is called hepatic steatosis, or fatty liver.

The most common form is now called metabolic dysfunction–associated steatotic liver disease (MASLD). It was previously known as non-alcoholic fatty liver disease (NAFLD). In 2023, international liver societies agreed on new names to describe the disease more accurately and to avoid stigmatizing wording. The older name is still widely used, and in most cases the two terms describe the same condition.

MASLD is linked to excess body weight, type 2 diabetes, high blood pressure and abnormal cholesterol or blood fats. It is one of the most common liver conditions in the world, affecting roughly 3 in 10 adults globally, according to large published reviews. Many people have no symptoms for years.

For most people, fatty liver is a mild, stable condition. In a minority, the fat triggers inflammation and scarring that can lead to cirrhosis, liver failure or liver cancer. The good news is that fatty liver is largely reversible in its early stages with lifestyle changes, especially weight loss, healthy eating and regular exercise.

Simple fatty liver (steatosis alone) usually does not progress. MASH is the more serious form, because inflammation can lead to scarring (fibrosis) and cirrhosis.

The liver stores and processes fat and sugar. In MASLD, a combination of factors causes fat to accumulate in liver cells:

• Insulin resistance: The body’s cells respond poorly to insulin. This raises blood sugar and insulin levels and promotes fat production in the liver, and fat breakdown in other tissues sends more fatty acids to the liver.
• Excess calories and sugar: The liver converts surplus sugar, especially fructose from sugary drinks, into fat.
• Fat tissue changes: Excess abdominal (visceral) fat releases fatty acids and inflammatory chemicals that reach the liver.
• Gut and genetic factors: Changes in gut bacteria and inherited gene variants (such as PNPLA3) influence who develops fatty liver and who progresses to scarring.

In some people, fat buildup injures liver cells, which triggers inflammation (MASH). Ongoing inflammation leads to scar tissue (fibrosis), and extensive scarring becomes cirrhosis.

Stages of progression

• Simple fatty liver (steatosis): Fat in the liver with little or no inflammation
• MASH: Fat with inflammation and liver cell damage
• Fibrosis: Scar tissue forms, graded from F0 (none) to F4 (cirrhosis)
• Cirrhosis: Widespread scarring that disrupts liver structure and function
• Complications: Liver failure, liver cancer and portal hypertension

Fibrosis is the most important factor in predicting long-term outcomes. The earlier stages can often improve or reverse with treatment.

Main risk factors

• Overweight and obesity, especially excess fat around the abdomen
• Type 2 diabetes and prediabetes
• Insulin resistance and metabolic syndrome: A cluster that includes a large waist, high blood pressure, high blood sugar, high triglycerides and low HDL cholesterol
• High blood pressure
• High triglycerides or abnormal cholesterol
• Age, with risk increasing in middle age and later, though it can affect children and young adults
• Sedentary lifestyle
• Unhealthy diet: High in sugary drinks, refined carbohydrates, ultra-processed foods and saturated fat
• Obstructive sleep apnea
• Polycystic ovary syndrome (PCOS)
• Underactive thyroid (hypothyroidism)
• Family history and genetic factors
• Ethnic background: Higher rates have been reported in people of Hispanic and South Asian ancestry, among others

Lean MASLD

MASLD can also occur in people with a normal body weight, particularly in some Asian populations. In these people, genetic factors, visceral fat, insulin resistance and diet play a role.

Other causes of fatty liver

Not all fatty liver is MASLD. Other causes include heavy alcohol use, certain medicines (such as long-term corticosteroids, tamoxifen, methotrexate and amiodarone), rapid weight loss, malnutrition, hepatitis C, Wilson disease, pregnancy-related liver conditions and some rare metabolic diseases. A doctor needs to exclude these.

Most people with fatty liver have no symptoms. It is often found by chance, from abnormal liver blood tests or an ultrasound done for another reason.

When symptoms do occur, they are usually vague and may include:

• Fatigue
• A dull ache or fullness in the upper right abdomen
• General discomfort
• Darkened patches of skin, usually in the neck folds or armpits (acanthosis nigricans), linked to insulin resistance

Signs of advanced liver disease

If fatty liver progresses to cirrhosis, signs can include:

• Yellowing of the skin and eyes (jaundice)
• Swollen abdomen (ascites) or swollen legs
• Itching
• Easy bruising or bleeding
• Spider-like blood vessels on the skin
• Confusion or drowsiness (hepatic encephalopathy)
• Vomiting blood or passing black stools

When to see a doctor

See a doctor if you have risk factors such as type 2 diabetes, obesity or metabolic syndrome, if a blood test or scan shows liver abnormalities, or if you have persistent upper abdominal discomfort or unexplained tiredness.

Seek urgent medical care if you have yellow skin with confusion, vomiting blood, black stools, severe abdominal pain or a rapidly swelling abdomen.

• Medical history and examination: The doctor asks about weight changes, diet, alcohol intake, medicines, family history and other conditions. They check weight, waist size, blood pressure and signs of liver disease.
• Blood tests:

• Liver enzymes (ALT and AST): May be mildly raised, but can also be normal even in advanced disease
• Blood sugar and HbA1c, cholesterol and triglycerides, to look for metabolic risk factors
• Tests to exclude other causes: Hepatitis B and C, iron studies, autoimmune markers and others when appropriate
• Imaging:

• Ultrasound: Often the first test. Fat makes the liver appear brighter, but it is less reliable for mild fat.
• CT or MRI: Can show fat in the liver, and MRI-based tests (such as MRI-PDFF) measure fat quite precisely
• Assessing fibrosis (scarring): This is the most important step.

• FIB-4 score: A simple calculation from age, AST, ALT and platelet count. It is often used as a first step to identify people who need further testing.
• Elastography (such as FibroScan): A painless test that measures liver stiffness
• Blood-based tests: Such as the ELF test
• Liver biopsy: A tiny sample of liver tissue is examined under a microscope. It is used when the diagnosis or stage is unclear after other tests, and it remains the definitive way to confirm MASH and grade scarring.

The main treatment for MASLD is lifestyle change. Medicines are used in selected people, mainly those with MASH and significant fibrosis. Treatment also aims to control related conditions such as diabetes, blood pressure and cholesterol.

Weight loss

Losing weight is the most effective treatment for fatty liver. Research shows a clear dose-response pattern:

• About 5% weight loss can reduce liver fat
• About 7% to 10% can improve inflammation and liver cell injury
• About 10% or more can improve fibrosis in many people

Weight should be lost gradually, around 0.5 to 1 kilogram (1 to 2 pounds) per week. Very rapid weight loss can sometimes worsen liver inflammation.

Healthy eating

• Follow a Mediterranean-style diet, rich in vegetables, fruit, whole grains, legumes, nuts, fish and olive oil. It reduces liver fat even without weight loss.
• Cut back on sugary drinks, including soft drinks, sweetened juices and energy drinks, as well as added sugars and refined carbohydrates
• Limit ultra-processed foods, fried foods and processed meats
• Reduce saturated fat from red meat, butter and full-fat processed dairy
• Watch portion sizes and overall calories if weight loss is needed
• Coffee: Studies link regular coffee drinking with a lower risk of liver scarring. It can be part of a healthy diet if you tolerate it and your doctor agrees.

No single food or supplement treats fatty liver, and there are no proven “liver detox” diets.

Physical activity

• Aim for at least 150 minutes of moderate-intensity activity per week, such as brisk walking, cycling or swimming
• Add strength training two or more times a week
• Exercise reduces liver fat even if no weight is lost
• Reduce long periods of sitting

Alcohol

Because alcohol can worsen liver injury, doctors usually advise limiting or avoiding it in fatty liver disease. People with MASH, fibrosis or cirrhosis are generally advised to avoid alcohol completely. Ask your doctor what is right for you.

Medicines

• Resmetirom: A once-daily tablet approved in the United States in 2024 for adults with MASH and moderate to advanced (non-cirrhotic) fibrosis. Approval in other countries varies.
• Semaglutide (a GLP-1 receptor agonist): Approved in the United States in 2025 for adults with MASH and moderate to advanced fibrosis. These medicines also help with weight loss and diabetes.
• Other diabetes medicines: Some, such as pioglitazone and GLP-1 or SGLT2 drugs, may benefit the liver in people with type 2 diabetes. A doctor chooses the best option.
• Vitamin E: May be used in selected people with biopsy-proven MASH who do not have diabetes. It is not suitable for everyone, so it should only be taken with medical guidance.
• Statins: People with fatty liver often need cholesterol-lowering medicines to lower heart disease risk. Statins are generally safe in fatty liver disease and should not be avoided just because of raised liver enzymes.

Drug options are changing quickly, so ask your doctor or a liver specialist what is currently available and appropriate.

Weight-loss procedures

For people with severe obesity, bariatric (weight-loss) surgery and some endoscopic procedures can lead to major improvements in liver fat, inflammation and fibrosis, and often in diabetes.

Advanced disease

• Cirrhosis: Needs regular monitoring and management of complications, including screening for varices and liver cancer
• Liver transplant: Considered for liver failure or cirrhosis with serious complications

• Cirrhosis and liver failure
• Liver cancer (hepatocellular carcinoma): Can occur mainly in cirrhosis, but in MASLD it can sometimes develop even without cirrhosis
• Portal hypertension: Raised pressure in the liver’s blood vessels, causing swollen veins that can bleed, fluid buildup and an enlarged spleen
• Cardiovascular disease: Heart attack and stroke are the leading cause of death in people with MASLD, more so than liver disease itself
• Type 2 diabetes and chronic kidney disease: Fatty liver is linked with higher risk of both
• Certain cancers outside the liver, such as colorectal cancer, which is more common in people with metabolic risk factors

• Set realistic goals. Gradual, sustainable changes work better than crash diets.
• Keep regular check-ups and blood tests, and ask your doctor how often liver fibrosis should be reassessed. This depends on your risk.
• Keep blood pressure, blood sugar and cholesterol under control, and take medicines as prescribed.
• Do not smoke. Smoking increases the risk of liver scarring and heart disease.
• Check with a doctor or pharmacist before taking any medicine, herbal product or supplement. Some can harm the liver. Do not exceed the recommended dose of acetaminophen (paracetamol).
• Get vaccinated against hepatitis A and B if you are not immune, as advised by your doctor.
• Get enough sleep, and ask your doctor about sleep apnea if you snore heavily or feel very sleepy in the day.
• Seek support. Weight, diet and lifestyle changes can be hard, and dietitians, exercise professionals, counseling and support groups can help. Fatty liver should never be a reason for blame or shame.

• Maintain a healthy weight, especially avoiding fat around the waist
• Eat a balanced diet that is high in plant foods and low in sugary drinks, refined carbs and ultra-processed foods
• Stay physically active and reduce sitting time
• Limit alcohol
• Control related conditions: Diabetes, high blood pressure and abnormal cholesterol
• Avoid unnecessary medicines and supplements that can harm the liver
• Get screened if you are at risk. People with type 2 diabetes, obesity with other metabolic risks, or abnormal liver tests may benefit from a liver check, such as FIB-4 followed by elastography when needed
• Encourage healthy habits in children. Childhood obesity is a major driver of fatty liver in young people

• “Fatty liver only happens to people who drink alcohol.” MASLD occurs in people who drink little or no alcohol. It is mainly linked to metabolic factors.
• “Fatty liver is harmless.” Many people have mild disease, but a minority develop MASH, cirrhosis or liver cancer, and heart disease risk is higher.
• “Only overweight people get fatty liver.” Most people with MASLD are overweight, but lean people can also develop it.
• “If my liver enzymes are normal, my liver is fine.” Liver enzymes can be normal even with fibrosis. Fibrosis tests give more reliable information.
• “Fatty liver can’t be reversed.” Early fatty liver can often improve or resolve with weight loss and lifestyle change. Even some fibrosis can improve.
• “Fat-free or low-fat diets are the best fix.” The type of food matters more than fat alone. Added sugars, refined carbs and ultra-processed foods are major drivers, and healthy fats such as olive oil and nuts are beneficial.
• “Detox cleanses and liver supplements cure fatty liver.” There is no evidence for this, and some products can harm the liver.
• “Fatty liver is contagious.” It is not an infection and cannot be passed on to others.
• “Only adults get fatty liver.” Children and teenagers can also develop it, especially with obesity.

What is the difference between NAFLD and MASLD?

They describe largely the same condition. MASLD is the newer name and requires evidence of at least one metabolic risk factor, while NAFLD was defined mainly by what it was not (not caused by alcohol). The new names also drop the word “fatty” in some terms to be less stigmatizing.

What is the difference between fatty liver and MASH?

Fatty liver (steatosis) means fat in the liver. MASH means fat plus inflammation and liver cell damage, which can lead to scarring. MASH is the more serious form.

Can fatty liver be reversed?

Yes, often in the early stages. Losing 5% to 10% or more of body weight, eating healthily and exercising can reduce or remove liver fat and improve inflammation. Advanced scarring is harder to reverse, though it can sometimes improve.

How long does it take to reverse fatty liver?

It varies. Liver fat can start to fall within weeks of lifestyle changes, but it may take months of sustained effort to see major improvement. Long-term maintenance is important.

Does fatty liver cause weight gain or belly fat?

Fatty liver is usually a result of excess weight and insulin resistance rather than the cause. They influence each other, however, and a larger waist often goes along with a fatty liver.

Can I drink alcohol with fatty liver?

Alcohol adds extra stress to the liver. Many doctors recommend avoiding it or keeping it to a minimum, and people with MASH, fibrosis or cirrhosis should avoid alcohol completely. Discuss your situation with your doctor.

Is fatty liver painful?

Usually not. Some people feel mild discomfort in the upper right abdomen. Significant pain needs medical attention.

Is coffee good for fatty liver?

Studies link regular coffee drinking with a lower risk of liver fibrosis, but it is not a treatment. If coffee suits you, it can be part of a healthy routine. Avoid adding large amounts of sugar or cream.

Can children have fatty liver?

Yes. It is increasingly seen in children and teenagers with obesity. Healthy eating, physical activity and family-based support are the main treatments.

How often should I get my liver checked?

It depends on your risk and results. People with diabetes, obesity or raised liver tests may need periodic fibrosis assessment, every one to three years or as your doctor advises. People with advanced fibrosis or cirrhosis need more frequent monitoring.

Will I need a liver transplant?

Most people with fatty liver never need one. A transplant is considered only if the disease progresses to severe cirrhosis or liver failure.

• AASLD, EASL, EASD and EASO clinical practice guidelines on MASLD: https://www.aasld.org and https://easl.eu
• National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Nonalcoholic Fatty Liver Disease (NAFLD) and MASH: https://www.niddk.nih.gov/health-information/liver-disease/nafld-nash
• American Liver Foundation. Fatty Liver Disease: https://liverfoundation.org
• Rinella ME, et al. A multisociety Delphi consensus statement on new fatty liver disease nomenclature. Journal of Hepatology, 2023.
• World Health Organization. Obesity and overweight: https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight

This article is for general educational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Fatty liver care depends on the stage of the disease, other health conditions and the individual, so always talk to a qualified healthcare professional about your own symptoms, test results, diet, exercise and treatment choices. If you have yellow skin with confusion, vomiting blood, black stools, severe abdominal pain or any other medical emergency, contact your local emergency services or seek urgent care immediately.