Metabolic dysfunction-associated steatotic liver disease (MASLD), formally called nonalcoholic fatty liver disease (NAFLD), is a chronic condition that can lead to liver inflammation, damage, and scarring if untreated.

MASLD affects about 40% of adults and up to 14% of children and adolescents around the world. It’s more common in people with type 2 diabetes and obesity, but it can also develop in people without these risk factors.

MASLD happens when fat builds up in your liver for reasons unrelated to alcohol. It’s often linked to metabolic factors, such as:

  • overweight or obesity
  • high blood sugar
  • high cholesterol
  • high triglycerides
  • high blood pressure

Other health conditions can also lead to fat buildup in your liver, including metabolic dysfunction, alcohol-associated liver disease, and rare genetic disorders.

Early treatment is important to help prevent complications. Management usually involves weight loss and lifestyle changes, and in some cases, your doctor may recommend medication to address risk factors, symptoms, or complications of MASLD.

Read on to find answers to some of the most common questions about MASLD.

To test for MASLD, your doctor will start with a physical exam and questions about your medical history and lifestyle. This helps them identify risk factors or symptoms.

They may order blood tests to check your liver enzymes, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST). High liver enzymes can be a sign of MASLD or another health condition.

If your results show elevated enzymes, your doctor may recommend additional tests, including:

  • blood tests to look for infections or other health conditions
  • imaging tests, such as an ultrasound or MRI, to check for fat buildup or other changes in your liver
  • liver biopsy, where a small tissue sample is collected and examined under a microscope

Talk with your doctor about which tests they recommend and what each one involves.

Although MASLD is more common in people who have overweight or obesity, it also affects about 10% to 15% people who are lean or thin.

Risk factors for MASLD in lean people include:

  • high triglycerides
  • high cholesterol
  • prediabetes or type 2 diabetes

Certain gene variants may also raise the risk of MASLD.

Keep in mind that MASLD isn’t the only condition that can cause fat buildup in the liver. Other potential causes include:

  • celiac disease
  • rare genetic disorders, such as:
    • glycogen storage disorders
    • hemocystinuria
    • Wilson disease
  • severe malnutrition
  • rapid weight loss
  • taking certain medications, such as:
    • tamoxifen
    • amiodarone
    • methotrexate

These conditions can affect people of any body size.

MASLD likely develops from a combination of lifestyle, environmental, and genetic factors.

A 2025 research review identified several genes that may influence MASLD risk, including:

  • PNPLA3
  • TM6SF2
  • MBOAT7
  • GCKR
  • HSD17B13

Certain variants of these genes may raise the risk of developing MASLD or increase the chances it will progress to metabolic dysfunction–associated steatohepatitis (MASH).

MASLD can range from mild to serious.

The earliest stage involves fat buildup without liver damage or scarring. With lifestyle changes or other treatments, this stage can often be reversed or prevented from getting worse.

MASH is a more advanced stage of MASLD. It occurs when fat buildup leads to liver inflammation and cell damage.

MASH can cause scarring, known as fibrosis. Mild fibrosis may improve with treatment or be prevented, but more severe fibrosis is harder to manage.

The most advanced stage is cirrhosis. At this point, scar tissue prevents the liver from working properly and can lead to liver cancer or liver failure.

MASLD may be reversible with early treatment. In its early stages, treatment can often reverse fat buildup in the liver or prevent it from getting worse.

If treatment is delayed, MASLD can progress to MASH, which may cause liver scarring and other complications.

Treatment may help repair mild liver scarring, but more severe scarring is harder to reverse.

Depending on your needs, your doctor may recommend weight loss, lifestyle changes, or medication.

Managing metabolic risk factors is the best way to help prevent MASLD.

Your doctor may recommend strategies to manage your:

  • weight
  • blood sugar
  • cholesterol
  • triglycerides
  • blood pressure

They may include lifestyle changes, medication, or other treatments.

Healthy lifestyle habits can also lower your risk of MASLD or keep it from getting worse. These could include:

  • getting regular exercise
  • limiting the amount of time you spend sitting each day
  • cutting back on saturated and trans fats, added sugars, and refined grains
  • eating nutrient-rich foods, such as fruits, vegetables, legumes, whole grains, nuts, seeds, and lean proteins
  • limiting or avoiding alcohol
  • avoiding smoking
  • getting enough high quality sleep

Talk with your doctor to learn more about risk factors for MASLD and how to manage them.

MASLD, previously known as NAFLD, is a chronic liver condition that can lead to liver damage and scarring if untreated.

A combination of lifestyle, environmental, and genetic factors can raise your risk. While obesity and type 2 diabetes are the most common risk factors, lean people without diabetes can also develop MASLD.

Doctors often use liver enzyme tests and follow-up exams to check for MASLD and identify possible complications.

Managing your weight and other risk factors is key to both prevention and treatment. Your doctor may recommend lifestyle changes, weight loss, medication, or other approaches to help prevent, reverse, or slow the condition.