Definition & Facts of NAFLD & NASH in Children

In this section:

What is NAFLD?

Nonalcoholic fatty liver disease (NAFLD) is a condition in which excess fat is stored in the 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. Children typically develop one type of NAFLD or the other, although sometimes children with one form are later diagnosed with the other form of NAFLD. Simple fatty liver is a mild condition, and NASH is a more serious one.

Simple fatty liver

Simple fatty liver is the form of NAFLD in which a child has increased fat in the liver but little or no inflammation or liver cell damage. Simple fatty liver typically doesn’t progress to cause permanent liver damage or complications.


NASH is the form of NAFLD in which a child has hepatitis—inflammation of the liver—and liver cell damage, in addition to fat in the liver. Inflammation and liver cell damage can cause fibrosis, or scarring, of the liver. If the damage and scarring are severe enough, NASH may lead to cirrhosis or liver cancer.

Experts do not know for sure why some children with fat in the liver have NASH while others have simple fatty liver alone.

How common are NAFLD and NASH in children?

NAFLD is the most common cause of chronic liver disease in children in the United States. Researchers estimate that close to 10 percent of U.S. children ages 2 to 19 have NAFLD.1 NAFLD has become more common in children in recent decades, in part because childhood obesity has become more common.

In a study of NAFLD in children, about 23 percent of those with excess fat in the liver had NASH.1

Who is more likely to develop NAFLD or NASH?

Children who have certain conditions, including obesity and conditions that are related to obesity, are more likely to develop NAFLD or NASH.

NAFLD and NASH are more common in older children than in younger children. NAFLD is more common in boys than in girls. However, among children with NAFLD, girls and boys are equally likely to have NASH.

Although NAFLD and NASH occur in children of all races and ethnicities, these conditions are most common in Hispanic children and Asian American children, followed by Caucasian children. NAFLD and NASH are less common in African American children.1

Boy who is overweight.
NAFLD and NASH are more common in older children than in younger children and more common in boys than in girls.

What are the complications of NAFLD and NASH?

Children with NAFLD and NASH have a greater chance of developing liver complications and other health problems.

Liver complications

The majority of children with NAFLD have simple fatty liver.1 Children with simple fatty liver typically don’t develop liver complications, although they have a higher risk for other health problems such as diabetes. However, some children with NAFLD have NASH. NASH can lead to liver complications such as cirrhosis and liver cancer. If cirrhosis leads to liver failure, a liver transplant may be needed.

Compared with people who develop NAFLD during adulthood, people who develop NAFLD during childhood are more likely to have NASH and related complications or liver disease as adults. Children with NASH may develop cirrhosis during childhood.2 However, the complications of cirrhosis, such as liver failure and liver cancer, usually arise in adulthood.

Other health problems

Children with NAFLD—either simple fatty liver or NASH—have a higher risk for certain health problems, including

Persons with the metabolic syndrome have a greater chance of heart disease, stroke and hardening of the arteries as adults.


Last Reviewed November 2017

This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.

The NIDDK would like to thank:
Jeffrey B. Schwimmer, M.D., University of California, San Diego, School of Medicine