What Is Nonalcoholic Fatty Liver Disease? Symptoms and Causes of NAFLD

Fatty liver disease is a condition caused by the buildup of extra fat in the liver. Also known as steatosis, fatty liver disease is relatively common and often doesn’t generate any symptoms. Most people don’t know they have it until it progresses and begins damaging the liver.1

In this article, we’ll discuss the two main types of fatty liver disease, what causes them, and the symptoms to look out for. If you’re at a higher risk of developing this condition, it’s important to know what to look out for and how to manage it.

What Is Fatty Liver Disease?

Your liver is an essential organ responsible for several functions, including creating bile to aid with digestion, storing iron, and creating energy from food. Since your liver helps process what you eat and drink, your diet can have a direct impact on its health.1

Normally, your liver contains only a small percentage of fat. However, poor diet choices and obesity can cause fat to build up, damaging your liver over time. According to the Cleveland Clinic, this buildup can become harmful once the fat makes up from 5 to 10 percent of your liver’s weight.1

Types of Fatty Liver Disease

Fatty liver disease can be broken down into two conditions — alcohol-associated liver disease (formerly called alcoholic fatty liver disease) and nonalcoholic fatty liver disease (NAFLD).

As the name suggests, alcohol-associated liver disease is caused by heavy drinking. The National Institute on Alcohol Abuse and Alcoholism (NIAAA) defines heavy drinking as:2

  • More than 4 drinks in one day or more than 14 drinks per week for men
  • More than 3 drinks in one day or more than 7 drinks per week for women

Alcohol-associated liver disease affects around 5 percent of people in the United States.1

On the other hand, NAFLD isn’t caused by drinking alcohol, but may instead be caused by excess body weight, diabetes, or other health complications. NAFLD is extremely common, affecting around 24 percent of adults and 10 percent of children in the U.S.3,4

What Causes Fatty Liver Disease?

Some people with NAFLD develop the condition without any underlying cause. However, most people have at least one risk factor that increases their likelihood of developing the disease. Risk factors include:4

  • Taking certain medications, such as tamoxifen (breast cancer treatment), diltiazem (blood pressure treatment), or amiodarone (arrhythmia or abnormal heartbeat treatment)
  • Having insulin resistance (your cells can’t properly use insulin to turn sugar or glucose into fuel) or type 2 diabetes
  • Having metabolic syndrome, a condition caused by a combination of high blood pressure, high cholesterol, high triglycerides, and insulin resistance
  • Being menopausal or postmenopausal (no longer having periods)
  • Being overweight or obese, especially with excess belly fat
  • Having sleep apnea, a condition that causes you to stop breathing while sleeping
  • Being of Asian or Hispanic descent
  • Eating a diet high in sugar

Symptoms of NAFLD

Most people aren’t aware they have NAFLD because it rarely causes symptoms. However, if it’s left untreated, NAFLD can eventually cause inflammation and liver scarring. This is known as non-alcohol-related steatohepatitis (NASH), which may be associated with symptoms including:5

  • Pain and swelling in your upper right abdomen
  • Yellow-colored skin and eyes (jaundice)
  • Enlarged spleen (splenomegaly)
  • Red palms
  • Swollen or enlarged blood vessels that are visible underneath your skin

Diagnosing NAFLD

When diagnosing NAFLD, your doctor will take into account your medical history, physical exam, and the results of blood and imaging tests.6 Your doctor will ask about your health history and any risk factors of NAFLD you may have. They may also ask about your diet to determine if it’s contributing to your risk.

During the physical exam, your doctor will check for any signs of NASH or cirrhosis, such as swelling in your abdomen or legs, jaundice, and an enlarged liver or spleen.

A blood test may be done to check your liver enzyme levels. NAFLD can cause high levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Blood tests can be used to suggest how diseased the liver is, evaluate for underlying causes of the liver disease, and sometimes avoid liver biopsy, especially when used in combination with imaging.7

Imaging tests are also used to visualize your liver to check for fat deposits, swelling, or structural changes. Your doctor may order the following:

  • Computed tomography (CT) scan: Uses x-rays to create detailed images of your liver
  • Magnetic resonance imaging (MRI): Uses radio waves and extremely strong magnets to generate three-dimensional (3D) images without x-rays
  • Ultrasound: Uses sound waves that bounce off your liver and travel back to the wand (transducer), creating images of your liver

If your doctor suspects that your NAFLD has progressed to NASH, they may order a biopsy. This is the only test that can confirm you have inflammation and or fibrosis. During a biopsy, your doctor will take a small piece of liver tissue using a long needle. A pathologist who specializes in diagnosing diseases with biopsies will look at the tissue under a microscope to determine if you have NASH.

Complications of NAFLD

In most cases, NAFLD is a mild disease, and many people can live long lives without any complications. However, 5 to 12 percent of those with NASH will eventually develop cirrhosis.5 If left untreated, NASH can eventually progress into cirrhosis or end-stage liver disease caused by significant scarring. Cirrhosis interferes with the liver’s ability to function and, in some cases, may result in liver failure.

Fortunately, liver fibrosis and inflammation can be reversed when diagnosed and treated early.

Resources for Living with Fatty Liver Disease

If you or a loved one is living with fatty liver disease, there are many resources providing information on treatments and living a healthy life with NAFLD.