What Is Nonalcoholic Fatty Liver Disease?

Nonalcoholic fatty liver disease (NAFLD) is the accumulation of fat in the liver caused by a buildup of fat in the body that isn’t related to alcohol consumption. It’s a chronic liver disease, affecting almost 1 out of 4 people in the US, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

While it’s normal and healthy for the liver to contain some fat, if more than 5 to 10 percent of the liver’s weight is fat, it’s called a fatty liver, also known as steatosis, notes the American Liver Foundation.

When inflammation and liver cell damage occur along with fat in the liver, it’s called nonalcoholic steatohepatitis (NASH). Per the NIDDK, NASH is a type of nonalcoholic fatty liver disease, and it affects about 1 out of 5 people with NAFLD.

According to a review in the World Journal of Gastroenterology, it's estimated that by 2030, NASH will be the number one reason for liver transplants in the United States.

Nonalcoholic Fatty Liver Disease vs. Alcohol-Associated Fatty Liver Disease

NAFLD and alcohol-associated fatty liver disease are the two most common forms of chronic liver disease in the United States right now, according to Christina Lindenmeyer, MD, a gastroenterologist at the Cleveland Clinic in Ohio.

The primary difference is indicated in the names of the diseases: Alcohol-associated fatty liver disease is linked with alcohol ingestion, and nonalcoholic fatty liver disease is associated with metabolic syndrome — a group of health risks that includes obesity, high cholesterol, high blood pressure, high blood sugar, and a large waistline — says Dr. Lindenmeyer.

The main way the two diseases are diagnosed is through a person’s medical history and how much alcohol the person consumes.

Risk Factors for Nonalcoholic Fatty Liver Disease

The cluster of conditions known as metabolic syndrome increase the risk of developing NAFLD and can include:

• Being Overweight The entire spectrum of obesity, ranging from overweight (body mass index, or BMI, of 25 or over), to obese (BMI of 30 or greater) and severely obese (BMI of 35 or greater) is associated with NAFLD, according to the American Association for the Study of Liver Diseases
• Large Waist Circumference A study presented at the International Liver Congress in Barcelona, Spain, found that waist circumference could be a better predictor of complications of NAFLD than BMI. Women whose waist measured greater than 35 inches and males whose waist measured more than 40 inches were at a greater risk.
• Type 2 Diabetes It is estimated that as many as 2 out of 3 people with type 2 diabetes have NAFLD. The relationship between these two conditions is considered bidirectional, which means that having NAFLD puts a person at higher risk for developing type 2 diabetes as well, notes the American Liver Foundation.
• Dyslipidemia High triglyceride levels and low levels of the “good” cholesterol, called high-density lipoprotein (HDL), are common in people with NAFLD.
• High Blood Pressure Even in the absence of other metabolic risk factors, hypertension, also known as high blood pressure, is associated with a higher risk of developing NAFLD, according to a cohort study published in the Journal of Hypertension.
• Older Age The incidence of fatty liver increases with age. Peak prevalence in men happens between ages 40 and 49, and for women between ages 60 and 69, according to research.

What Are the Symptoms of Nonalcoholic Fatty Liver Disease?

Many people with NAFLD don’t have any symptoms at all. If symptoms are present, they can include the following, according to the American Liver Foundation:

• Fatigue
• Weakness
• Weight loss
• Loss of appetite
• Nausea
• Abdominal pain

Nonalcoholic Fatty Liver Disease Diagnosis

Because many people with NAFLD have no symptoms, it’s often discovered as a result of testing for other conditions that might indicate a problem with the liver, notes the Mayo Clinic. The screening tests for NAFLD are simple blood tests that check liver biochemistries or tests of the liver function, says Lindenmeyer. These blood tests are often done as part of a routine physical exam. “If those results are abnormal, then frequently we follow that up with some sort of imaging study of the liver, whether it be an ultrasound, a CT (computerized tomography) scan, or an MRI (magnetic resonance imaging),” she says.

A Fibroscan device, which works like an ultrasound, may also be used to estimate the amount of scarring, or fibrosis, in the liver.

Nonalcoholic Fatty Liver Disease Treatment

Managing NAFLD involves reducing the fat build-up in the liver.

Along with losing weight, notes the American Liver Foundation, recommendations for managing NAFLD include:

• Consuming 800 units of vitamin E daily
• Regular aerobic exercise of at least 50 minutes, three times per week
• Eliminating alcohol
• If you have diabetes, tight control of glucose levels

Although there isn’t an FDA-approved drug to treat NAFLD, there are drugs in the pipeline that show promise but aren’t yet available, says Carlos Romero-Marrero, MD, director of the Liver Disease Center at Cleveland Clinic Florida, Tradition Hospital, in Port St. Lucie.

There is some evidence that weight-loss drugs such as semaglutide (Rybelsus) may be helpful in treating NAFLD and its more severe form, nonalcoholic steatohepatitis.

If a person with severe NAFLD is not able to lose weight through lifestyle changes, doctors may recommend bariatric (weight-loss) surgery.

Nonalcoholic Fatty Liver Disease Life Expectancy

Nonalcoholic Fatty Liver Disease Complications

If NAFLD progresses to NASH, in which inflammation causes damage and scarring in the liver, it can worsen over time and lead to cirrhosis — the replacement of healthy liver tissue with scar tissue.

People with cirrhosis are at a greater risk of developing liver failure and liver cancer. NAFLD and NASH are both associated with a higher-than-usual risk of cardiovascular disease. According to University of Michigan Health, heart disease is actually the leading cause of death for people with NAFLD.