Nonalcoholic fatty liver disease (NAFLD) is a condition in which excess fat is stored in your liver. This buildup of fat is not caused by 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). Simple fatty liver and NASH are two separate conditions. People typically develop one type of NAFLD or the other, although sometimes people with one form are later diagnosed with the other form of NAFLD.
Simple fatty liver, also called 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. Simple fatty liver typically does not progress to cause liver damage or complications.
NASH is a form of NAFLD in which you have hepatitis—inflammation of the liver—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 are not sure why some people with NAFLD have NASH while others have simple fatty liver.
NAFLD is one of the most common causes of liver disease in the United States. Most people with NAFLD have simple fatty liver. Only a small number of people with NAFLD have NASH. Experts estimate that about 20 percent of people with NAFLD have NASH. Between 30 and 40 percent of adults in the United States have NAFLD. About 3 to 12 percent of adults in the United States have NASH.
NAFLD is more common in people who have certain conditions, including obesity, and conditions that may be related to obesity, such as type 2 diabetes. Researchers have found NAFLD in 40 to 80 percent of people who have type 2 diabetes and in 30 to 90 percent of people who are obese. In research that tested for NAFLD in people who were severely obese and undergoing bariatric surgery, more than 90 percent of the people studied had NAFLD.
NAFLD can affect people of any age, including children. Research suggests that close to 10 percent of U.S. children ages 2 to 19 have NAFLD. However, people are more likely to develop NAFLD as they age.
While NAFLD occurs in people of all races and ethnicities, it is most common in Hispanics, followed by non-Hispanic whites. NAFLD is less common in African Americans. Asian Americans are more likely than people of other racial or ethnic groups to develop NAFLD when their weight is within the normal range.
The majority of people with NAFLD have simple fatty liver, and people with simple fatty liver typically don’t develop complications.
NASH can lead to complications, such as cirrhosis and liver cancer. People with NASH have an increased chance of dying from liver-related causes. If NASH leads to cirrhosis, and cirrhosis leads to liver failure, you may need a liver transplant to survive.
Studies also suggest that people with NAFLD have a greater chance of developing cardiovascular disease. Cardiovascular disease is the most common cause of death in people who have either form of NAFLD.
Usually, nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (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.
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 NAFLD—either simple fatty liver or NASH—if you
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.
In NAFLD, people have a buildup of fat in the liver that is not caused by alcohol use. If you have a history of heavy alcohol use and fat in your liver, your doctor may determine that you have alcoholic liver disease instead of NAFLD.
Experts are not sure why some people with NAFLD have NASH and others have simple fatty liver. Research suggests that certain genes may play a role.
People with NAFLD are more likely to have NASH if they have one or more of the following conditions:
Less common causes of NAFLD and NASH include
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 more likely to develop NAFLD. More research is needed on the link between gallbladder removal and NAFLD.
Doctors use your medical history, a physical exam, and tests to diagnose nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH).
Your doctor will ask if you have a history of health conditions that make you more likely to develop NAFLD and NASH, such as
Your doctor will ask about diet and lifestyle factors that may make you more likely to develop NAFLD and NASH, such as a lack of physical activity, eating a diet high in sugar and starch, or drinking sugary beverages.
Medical tests can’t show whether alcohol is the cause of fat in your liver. 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
Doctors use blood tests, imaging tests, and sometimes liver biopsy to diagnose NAFLD and NASH.
A health care professional may take a blood sample from you and send the sample to a lab. Your doctor may suspect you have NAFLD or NASH if your 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.
Your doctor may use the following imaging tests to help diagnose NAFLD:
A technician performs these tests in an outpatient center or a hospital. A technician can perform an ultrasound in a doctor’s office as well. A radiologist reads and reports on the images. You don’t need anesthesia, although you may receive light sedation during an MRI if you have a fear of confined spaces.
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.
During a liver biopsy, a doctor will take a piece of tissue from your liver. A pathologist will examine the tissue under a microscope to look for signs of damage or disease.
A doctor performs a liver biopsy at a hospital or an outpatient center. A health care professional will tell you how to prepare for a liver biopsy. You may need to stop taking certain medicines to prepare. You may be asked not to eat or drink anything for 8 hours before the procedure. During the procedure, you may receive a local anesthetic, sedatives, and pain medicine.
During the biopsy, you’ll lie on a table with your right hand resting above your head. The doctor will numb the area where he or she will insert the biopsy needle with a local anesthetic and then use the needle to take a small piece of liver tissue.
A liver biopsy is the only way to detect liver inflammation and damage 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.
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 fasting—eating and drinking nothing except water—can make NAFLD worse.
No medicines have been approved to treat NAFLD and NASH. However, 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 actually damage your liver.
If NASH leads to cirrhosis, doctors can treat the health problems caused by cirrhosis with medicines, operations, and other medical procedures. If cirrhosis leads to liver failure, you may need a liver transplant.
You may be able to prevent NAFLD and NASH by eating a healthy diet, limiting your portion sizes, and maintaining a healthy weight.
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