Fatty liver is the build-up of fat in the liver cells. Although this is not a normal condition, fat in the liver usually causes no damage by itself. However, on some occasions it can be a sign that other more harmful conditions are at work. It would seem logical that eating fatty foods would cause a fatty liver, but this is not the case. The liver does play an important role in the metabolism or breakdown of fats, but something goes wrong in this process of metabolism, although it is still not known what does cause fat to build-up in the liver. This condition is usually reversible when the underlying causes are treated or removed.

There are usually no symptoms that are noticeable to the patient. In fact, fatty liver is frequently uncovered during a routine physical examination. There may be a rise in certain liver enzymes found in the blood, and sometimes the liver is slightly enlarged. Fatty liver may also be discovered while the physician is evaluating a patient for other illnesses. For example, an ultrasound exam of the abdomen done for other reasons may show fat in the liver. To be certain of a diagnosis of fatty liver, the physician may recommend a liver biopsy. Under local anesthesia, a slender needle is inserted through the right lower chest. A small piece of liver tissue is taken out with the needle and examined under a microscope.

Steatohepatitis is inflammation of the liver related to fat accumulation. Heavy alcohol use can lead to fatty liver and inflammation, usually called alcoholic hepatitis. Steatohepatitis resembles alcoholic hepatitis, but it can and does occur in people who seldom or never drink alcohol. In this instance, it is often called nonalcoholic steatohepatitis or NASH. Both alcoholic hepatitis and steatohepatitis can lead to serious liver damage and cirrhosis.

Studies have shown that many people who are significantly overweight have developed, or will develop, steatohepatitis. It can also occur with rapid weight loss. Steatohepatitis has been connected to estrogen hormones in some women.

In most instances, treatment of fatty liver and steatohepatitis requires control of the underlying conditions. This may include reduction of high blood triglycerides, good control of diabetes, or not drinking alcohol. In some cases, surgical reversal of intestinal bypass for obesity is required.