About Non-Alcoholic Fatty Liver Disease (NAFLD)
Causes and Risk Factors for Fatty Liver Disease
Fatty liver disease, including MASLD (formerly called NAFLD), is usually linked to how the body handles sugar and fat. Common causes and contributors of fatty liver disease include:
- Insulin resistance: This means the body has trouble using insulin well. Insulin resistance can raise blood sugar and increase fat storage in the liver.
- Metabolic risk factors: Type 2 diabetes, prediabetes, high blood pressure, abnormal cholesterol or triglyceride levels, and excess weight—especially around the waist—can increase the chance of developing fatty liver disease.
- Genes and family history: Some people inherit gene differences that make fatty liver disease more likely or more likely to progress.
Risk factors of fatty liver disease that cannot be changed include:
- Age: Fatty liver disease is more common in adults in midlife and older age, although it can also occur in younger adults and children.
- Sex: Patterns may differ by sex and life stage. For example, risk can increase after menopause.
- Family history and genetics: Having a close family member with fatty liver disease, advanced liver scarring, or cirrhosis may increase risk.
Risk factors of fatty liver disease that can often be addressed or managed include:
- Excess body weight or waist size: Extra weight, especially around the belly, is a common risk factor. People at different body sizes can still develop fatty liver disease.
- Low physical activity: Regular movement can help reduce liver fat and improve how the body uses insulin, even if weight does not change much.
- Eating pattern: Diets high in sugary drinks, highly processed foods, refined carbohydrates, or excess calories can contribute to liver fat. A balanced eating pattern, such as a Mediterranean-style diet, may help.
- Other health conditions: Type 2 diabetes, prediabetes, high blood pressure, abnormal cholesterol or triglycerides, polycystic ovary syndrome, sleep apnea, and underactive thyroid may be linked with fatty liver disease.
These factors often overlap. The most important steps are to work with a healthcare professional to check liver health, manage related conditions such as diabetes or high cholesterol, avoid or limit alcohol as advised, and make gradual, sustainable lifestyle changes.
Symptoms of Fatty Liver Disease
Fatty liver disease often causes no symptoms, especially in the early stages. A person can have normal daily activities and still have liver fat or liver scarring.
When symptoms do happen, they may include:
- Tiredness or low energy
- Discomfort or a feeling of fullness in the upper right side of the abdomen
If fatty liver disease progresses to advanced scarring or cirrhosis, symptoms may include:
- Ongoing weakness or fatigue
- Unexplained weight loss
- Decreased appetite
- Jaundice (yellowing of the skin and eyes)
- Itchy skin
- Swelling in the legs, ankles, feet, or abdomen
- Easy bruising or bleeding, confusion, black stools, or vomiting blood
Fatty liver disease is also linked with heart and blood vessel disease, type 2 diabetes, chronic kidney disease, and sleep apnea. Contact a healthcare professional if you have risk factors, abnormal liver blood tests, or symptoms such as yellowing of the skin or eyes, swelling of the belly or legs, or severe itching. Seek urgent medical care for confusion, vomiting blood, black or bloody stools, severe abdominal swelling, or severe weakness.
How Fatty Liver Disease Is Diagnosed
There is no single test that diagnoses every case of fatty liver disease or shows how serious it is. A healthcare professional may use several types of information, including:
- Medical history: This includes alcohol use, medicines and supplements, family history, weight changes, and conditions such as diabetes, high blood pressure, and high cholesterol.
- Physical exam: The clinician may check for signs of liver disease and related conditions.
- Blood tests: These may include liver enzymes such as ALT and AST, platelet count, cholesterol and triglycerides, blood sugar tests, and tests to look for other causes of liver disease. Liver enzymes can be normal even when scarring is present.
- Imaging tests: Ultrasound, CT, MRI, or specialized tests such as vibration-controlled transient elastography may help detect liver fat and estimate liver stiffness, which can suggest scarring.
- Liver biopsy: This is not needed for everyone. It may be used when results are unclear or when a specialist needs to confirm MASH or determine the amount of inflammation and scarring.
To understand the stage or severity of fatty liver disease, including MASLD, additional tests may include:
- Fibrosis assessment: Non-invasive tests, such as FIB-4, NAFLD Fibrosis Score, Enhanced Liver Fibrosis blood test, FibroScan, or magnetic resonance elastography, may be used to estimate the risk of advanced scarring.
- Specialist referral: People with a higher risk of advanced scarring, uncertain results, or signs of cirrhosis may be referred to a liver specialist.
Your healthcare professional can explain which tests are appropriate for you and how often monitoring is needed.
Treatment Options for Fatty Liver Disease
Treatment for fatty liver disease focuses on lowering liver fat, reducing inflammation, preventing or slowing liver scarring, and managing health conditions that increase risk. The right plan depends on a person’s overall health, stage of liver disease, and preferences.
- Weight loss, if recommended: For people with excess body weight, losing at least 3% to 5% of body weight can reduce liver fat. Losing about 7% to 10% may be needed to improve liver inflammation and scarring. Weight loss should be gradual, because rapid weight loss can worsen liver problems.
- Eating pattern: A healthcare professional or dietitian may recommend a sustainable eating plan that limits sugary drinks, refined carbohydrates, and highly processed foods and emphasizes vegetables, fruits, whole grains, beans, nuts, fish, and healthy fats. A Mediterranean-style eating pattern is commonly recommended.
- Physical activity: Aerobic activity and strength training can lower liver fat and improve insulin resistance, even without major weight loss. Start slowly and ask a healthcare professional what level of activity is safe for you.
- Medicines and related conditions: Medicines may be used to treat diabetes, high blood pressure, high cholesterol, or obesity. Some diabetes and weight-management medicines may also improve liver-related measures in selected people. Resmetirom is approved for certain adults with MASH and moderate to advanced liver fibrosis who do not have cirrhosis. A liver specialist can help decide whether medication is appropriate.
- Alcohol, medicines, and supplements: Ask your healthcare professional whether you should avoid alcohol completely. Also check before taking herbal products, supplements, or new medicines, because some can harm the liver or interact with other treatments.
These recommendations should be personalized based on your health needs, test results, medicines, and goals. Your healthcare professional can help you decide which changes are most important and realistic for you.
Do not stop, start, or change medicines without talking with your healthcare professional. If you are prescribed a medicine for MASH or another health condition, ask how to take it, what side effects to watch for, and whether any monitoring is needed.