Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of liver disease in the United States. NAFLD is a condition in which fat builds up in the liver as a result of something other than heavy alcohol use. When heavy alcohol use causes fat to build up in the liver, this condition is called alcoholic liver disease.
Two types of NAFLD are simple fatty liver and nonalcoholic steatohepatitis (NASH). People typically develop one type or the other, although sometimes people with one form are later diagnosed with the other.
Simple fatty liver, also referred to as nonalcoholic fatty liver (NAFL), is a form of NAFLD in which you have fat in your liver but little or no inflammation or liver cell damage. Most people with NAFLD have simple fatty liver. Simple fatty liver typically does not progress to cause liver damage or complications, though studies suggest that people with NAFLD have a greater chance of developing cardiovascular disease.
NASH is a form of NAFLD in which you have inflammation and liver cell damage in addition to fat in your liver. Inflammation and liver cell damage can cause fibrosis, or scarring, of the liver. NASH may lead to cirrhosis or liver cancer.
Experts aren’t sure why some people with NAFLD have NASH while others have simple fatty liver. While NAFLD occurs in people of all races and ethnicities, it is most common in Hispanics, followed by non-Hispanic whites.
NAFLD can affect people of any age. It is more common in people who have certain conditions, including obesity and conditions that may be related to obesity, such as type 2 diabetes. People are more likely to develop NAFLD as they age.
Fatty Liver Symptoms
Usually NAFLD and NASH are silent diseases with few or no symptoms. You may not have symptoms even if you develop cirrhosis due to NASH.
If you do have symptoms, you may feel tired or have discomfort in the upper right side of your abdomen.
Fatty Liver Causes
Experts are still studying the causes of NAFLD and NASH. Research suggests that certain health conditions make you more likely to develop NAFLD or NASH.
You are more likely to develop either type of NAFLD if you:
- Are overweight or obese
- Have insulin resistance
- Have abnormal levels of fats in your blood, which may include high levels oftriglycerides or abnormal levels of cholesterol (high total cholesterol, high LDL cholesterol or low HDL cholesterol)
- Havemetabolic syndrome or one or more traits of metabolic syndrome (to learn about the signs and symptoms of metabolic syndrome, go to https://www.nhlbi.nih.gov/health/health-topics/topics/ms/signs)
- Have type 2 diabetes
Research also suggests that certain genes may make you more likely to develop NAFLD. Experts are still studying the genes that may play a role in NAFLD.
People with NAFLD are more likely to have NASH if they have one or more of the following conditions:
- Obesity, especially with a large waist size
- High blood pressure
- High levels of triglycerides or abnormal levels of cholesterol
- Type 2 diabetes
- Metabolic syndrome
Less common causes of NAFLD and NASH include:
- Disorders that cause your body to use or store fat improperly
- Rapid weight loss
- Certain infections, such as hepatitis C
- Certain medicines, such as amiodarone(Cordarone, Pacerone), diltiazem, glucocorticoids, highly active antiretroviral therapy, methotrexate (Rheumatrex, Trexall), synthetic estrogens, tamoxifen (Nolvadex, Soltamox) a valproic acid
- Exposure to some toxins
A study funded by the National Institute of Diabetes and Digestive and Kidney Diseases found that people who had surgery to remove their gallbladder were also more likely to develop NAFLD.
Fatty Liver Diagnosis
Doctors use your medical history, a physical exam, and tests to diagnose NAFLD and NASH.
Your doctor will ask if you have a history of health conditions that make you more likely to develop NAFLD and NASH. He or she will also ask about diet and lifestyle factors that may increase your risk, such as a lack of physical activity or a habit of drinking beverages with added sugar.
Medical tests can’t show whether alcohol is the cause of fat in your liver. So your doctor will ask about your alcohol intake to find out whether fat in your liver is a sign of alcoholic liver disease or NAFLD.
During a physical exam, a doctor usually examines your body and checks your weight and height to calculate your body mass index. Your doctor will look for signs of NAFLD or NASH, such as:
- An enlarged liver
- Signs ofinsulin resistance, such as darkened skin patches over your knuckles, elbows, and knees
- Signs ofcirrhosis, such as jaundice, a condition that causes your skin and whites of your eyes to turn yellow
Doctors use blood tests, imaging tests, and sometimes liver biopsy to diagnose NAFLD and NASH.
Your doctor may suspect you have NAFLD or NASH if a blood test shows increased levels of the liver enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Your doctor may perform additional blood tests to find out if you have other health conditions that may increase your liver enzyme levels.
Imaging tests used to help diagnose NAFLD include:
- Ultrasound uses a device called a transducer, which bounces safe, painless sound waves off your organs to create an image of their structure.
- Computerized tomography (CT) scans. CT scans use a combination of x-rays and computer technology to create images of your liver. For a CT scan, a health care professional may give you a solution to drink or an injection of a special dye, called contrast medium. Contrast medium makes the structures inside your body easier to see during the procedure.
- Magnetic resonance imaging (MRI). MRI machines use radio waves and magnets to produce detailed images of your organs and soft tissues without using x-rays. A health care professional may give you an injection of contrast medium when administering an MRI.
Imaging tests can show fat in your liver. These tests can’t show inflammation or fibrosis, so your doctor can’t use these tests to find out whether you have simple fatty liver or NASH. If you have cirrhosis, imaging tests may show nodules, or lumps, on your liver.
A liver biopsy is the only way to detect liver inflammation or damage and to diagnose NASH. Doctors don’t recommend this test for everyone with NAFLD. Your doctor may recommend a liver biopsy if you are more likely to have NASH or if your other tests show signs of advanced liver disease or cirrhosis.
During a liver biopsy, a doctor will insert a needle and remove a small piece of tissue from your liver for examination by a pathologist. You may need to stop taking certain medicines to prepare for the biopsy. You may be asked not to eat or drink anything for eight hours before the procedure. During the procedure, you may receive a local anesthetic, sedatives, or pain medicine.
Fatty Liver Treatment
Doctors recommend weight loss to treat nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Weight loss can reduce fat in the liver, inflammation, and fibrosis, or scarring.
If you are overweight or obese, losing weight by making healthy food choices, limiting portion sizes, and being physically active can improve NAFLD and NASH. Losing at least 3 to 5 percent of your body weight can reduce fat in the liver. You may need to lose up to 10 percent of your body weight to reduce liver inflammation.
Doctors recommend gradually losing 7 percent of your body weight or more over the course of 1 year. Rapid weight loss through very low calorie diets or fasting can make NAFLD worse.
No medicines have been approved to treat NAFLD or NASH, but researchers are studying medicines that may improve these conditions. Some studies suggest that pioglitazone (Actos), a medicine for type 2 diabetes, improves NASH in people who don’t have diabetes. Researchers need more information to find out whether this medicine is safe and effective for long-term use in people with NASH.
A study by the National Institute of Diabetes and Digestive and Kidney Diseases’ NASH Clinical Research Network found that treatment with vitamin E or pioglitazone improved NASH in about half of the people treated. Doctors may recommend vitamin E for people who have NASH and don’t have diabetes or cirrhosis. Talk with your doctor before taking vitamin E or pioglitazone.
For safety reasons, talk with your doctor before using dietary supplements, such as vitamins, or any complementary or alternative medicines or medical practices. Some herbal remedies can damage your liver.
Diet and nutrition
If you have NAFLD or NASH, your doctor may recommend gradually losing weight if you are overweight or obese. He or she may suggest limiting your intake of fats, which are high in calories.
Replacing saturated fats and trans fats in your diet with monounsaturated fats and polyunsaturated fats (found in vegetable oils, nuts, and oily fish), especially omega-3 fatty acids, may reduce your chance of heart disease if you have NAFLD.
Your doctor may suggest other dietary changes to help treat NAFLD and NASH, including:
- Eat more low glycemic-indexfoods, such as most fruits, vegetables, and whole grains. These foods affect your blood glucose less than high glycemic-index foods, such as white bread, white rice, and potatoes.
- Avoid foods and drinks that contain large amounts of simplesugars, especially Fructose is found in sweetened soft drinks, sports drinks, sweetened tea, and juices.
- Avoid heavy alcohol use, which can damage your For men, experts define heavy alcohol use as more than four drinks per day or more than fourteen drinks per week. For women, heavy alcohol use is more than three drinks per day or more than seven drinks per week.
Adapted from National Institute of Diabetes and Digestive and Kidney Diseases. “Nonalcoholic Fatty Liver Disease & NASH.” Accessed March 19, 2017. https://www.niddk.nih.gov/health-information/liver-disease/nafld-nash.