When someone is overweight or obese, too much fat can be stored in the liver. This can lead to a disease called nonalcoholic fatty liver disease, or NAFLD.
In some children and adults, the extra fat in the liver becomes a more severe problem, causing swelling and scar tissue. When this happens, it is called nonalcoholic steatohepatitis, (stee-at-oh-hep-a-titus), or NASH. Over time, NASH can lead to severe scarring, called cirrhosis (sir-oh-sis). Cirrhosis can lead to liver failure and loss of liver function.