Non-alcoholic fatty liver disease (NAFLD)

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science.

This page was reviewed on January 5, 2022.

Non-alcoholic fatty liver disease (NAFLD) is a condition that develops when fat builds up inside your liver beyond the normal amount (about 5 percent to 10 percent of its weight), according to the U.S. Department of Veterans Affairs. Over time, excess fat may harm the liver. You may have heard of fatty liver disease that’s caused by drinking too much alcohol—but, as the name implies, NAFLD has different causes.

About 24 percent of adults in the United States have NAFLD, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Both men and women are susceptible. It mostly occurs in middle-aged or older people. However, because of the obesity epidemic affecting people of all ages, it’s starting to be seen in children, too. While no ethnic group is immune, it’s more common in people of Hispanic descent.

NAFLD is the umbrella term for two types of this condition.

NAFL, or non-alcoholic fatty liver: With NAFL, your liver is enlarged and could cause discomfort, but it’s less likely to be inflamed or have damage, and you’re less likely to have complications.

NASH, or non-alcoholic steatohepatitis: This is the more severe form of NAFLD, with inflammation and damage as well as fat in your liver. The damage is seen as liver stiffness or scarring. In the advanced stage, this scarring is called cirrhosis. Cirrhosis can lead to liver failure, which requires a transplant. Up to 6.5 percent of Americans have this form of NAFLD, according to the NIDDK. It’s unclear why some people with NAFL progress to NASH and others don’t.

How NAFLD is diagnosed

Your doctor may suspect you have fatty liver disease if your routine blood tests show increased levels of liver enzymes.

Sometimes, fat in the liver is seen on imaging tests—such as an X-ray, an ultrasound, a computed tomography (CT) scan or a magnetic resonance imaging (MRI) scan—of your abdomen. It’s also possible to have fat in the liver yet have normal enzyme levels.

Depending on your test results, your doctor may order a FibroScan®, a type of ultrasound known as elastography. It uses sound waves to create images that measure the stiffness of liver tissue.

You may need to undergo a liver biopsy for a definitive diagnosis. During a biopsy, a needle is inserted into the liver through your abdomen, and sample cells are drawn out. The cells are sent to a laboratory where a pathologist examines them under a microscope.

Who’s at risk of developing NAFLD

It’s not known what exactly causes some people to develop NAFLD, but it’s seen in patients who are obese, especially those with a large waist.

You’re also at increased risk if you have:

  • Type 2 diabetes
  • High blood pressure
  • High amount of fats called triglycerides in your blood or low levels of the “good” HDL cholesterol
  • Obstructive sleep apnea
  • Polycystic ovary syndrome (PCOS)

What are the symptoms of NAFLD?

You can have NAFLD and not know because it doesn’t always cause symptoms. When they do occur, you may experience some fatigue and pain on the right side of your upper abdomen, especially if your liver is enlarged.

As it progresses, you may have:

  • Weight loss
  • Fluid in your stomach
  • Jaundice (yellowing of the skin or eyes)
  • Itchiness

Signs and symptoms of cirrhosis include:

  • Fatigue and weakness
  • Loss of appetite
  • Nausea
  • Weight loss
  • Swelling
  • Jaundice

What causes NAFLD?

The exact chain of events that leads to NAFLD is unknown, but there are theories. For example, there may be a link between NAFLD and insulin resistance, which is when your body doesn’t respond well to insulin.

Research has shown that there also may be a link between developing NAFLD and consuming too much iron, cholesterol and refined sugars in processed foods.

Other studies have identified genetic changes that may make some people more likely to develop NAFLD. One is a variation in the gene PNPLA3, which provides instructions for making a protein found in fat and liver cells. The variation may cause an increase in production of PNPLA3, which in turn leads to a decrease in the breakdown of fats in the liver.

NAFLD may run in some families. Environmental and lifestyle factors, such as a lack of exercise and poor diet, may also factor into who develops this condition.

Managing NAFLD

Because there are no Food and Drug Administration-approved medications for the treatment of NAFLD, one of the most helpful steps you can take is to lose weight. The aim should be to do so at a slow and steady pace of 1 to 2 pounds a week—any faster than that and you could worsen your NAFLD.

  • Be careful about the types of fats in your diet. Limit saturated fats such as red meat, butter and shortening, and avoid fried foods. Choose fat-free milk and other dairy products and foods with good-for-you fats, such as extra-virgin olive oil, flaxseed oil, and salmon and walnuts (both rich in omega-3 fatty acids). Other healthy foods include whole grains, fresh fruits and vegetables, and other high-fiber foods.
  • Work to manage chronic health conditions. For example, if you have diabetes, high cholesterol and/or high blood pressure, get them under control with diet and medications as needed.
  • Incorporate exercise as an important part of your health plan.
  • Take steps to protect your liver. That means no alcohol if you have NASH, abnormal liver enzymes, or hepatitis B or C. Your doctor may suggest no or limited amounts of alcohol if you have NAFL.
  • Be sure to review any over-the-counter medications you take (or want to take) with your doctor, since some may not be healthy for your liver.

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