Nonalcoholic Fatty Liver Disease: Overview and Risk Factors

Nonalcoholic fatty liver disease is the most common form of liver disease in the United States. As its name suggests, it is associated with abnormal fat accumulation in the liver.

Put simply, fatty liver develops from eating too much. When the amount of nutrients (particularly fat) entering the liver exceeds our ability to use it up, fat accumulates in the liver. A related cause is insulin resistance-the decreased ability of this hormone to clear nutrients from the bloodstream. Insulin increases the storage of fat in the liver.

Most patients do not have visible symptoms, although they may suffer from fatigue, malaise, and right-upper-abdominal discomfort. In more serious cases, the disease may result in hepatitis, liver failure, and/or cirrhosis.

Risk Factors

Obesity and related metabolic states
Elevated cholesterol, especially elevated triglycerides (the chemical form of fat in the body)
Total parenteral nutrition (intravenous feeding, as occurs in some hospitalized patients)
Drugs (e.g., amiodarone, tetracycline, glucocorticoids, synthetic estrogens, and certain pesticides)
Pregnancy: Rarely, fatty liver can occur during pregnancy.

Nonalcoholic Fatty Liver Disease: Diagnosis and Treatment

Diagnosis

The evaluation begins with a medical history and a physical examination.
Blood testing to assess liver function will be performed.
Ultrasound, CT scan, or MRI may make the diagnosis. These tests can identify fatty liver and evaluate for other disorders, including gallstones, hepatitis, and cirrhosis.
Liver biopsy may be recommended if the cause of fatty liver is unclear.

Treatment

Weight loss is essential in overweight patients. Even modest weight loss (about 5 percent of body weight) may have significant beneficial effects by reversing diabetes and hypertension.
Exercise may be beneficial, with or without associated weight loss.
Severely obese patients (BMI more than 35) may consider surgical options, such as "stomach stapling."
Diabetes mellitus should be treated as appropriate. Insulin-sensitizing drugs (e.g., metformin and pioglitazone) may be especially useful and are also under investigation for use in nondiabetic patients with fatty liver.
Treatment of high cholesterol and triglycerides may also be beneficial. Rarely, patients with advanced disease may require liver transplantation.

Nonalcoholic Fatty Liver Disease: Nutritional Considerations

Fatty liver disease is, in many cases, responsive to diet changes. Preliminary research suggests that weight reduction on a low-fat, high-fiber diet may be an effective treatment for nonalcoholic fatty liver diseases. Although further clinical trials are needed to establish the role of diet in treating these conditions, the key issues are as follows:

Weight loss: Loss of excess weight may reduce the risk for nonalcoholic fatty liver disease. Compared with a rate of 20 percent in the general population, nonalcoholic fatty liver disease affects up to 75 percent of obese individuals. Gradual, moderate weight loss (about 10 percent of body weight) may lead to improvement in liver function. However, rapid weight loss exceeding 1 pound per week in children and 3.5 pounds a week in adults may result in worsening of the disease.
Plant-based diets: Plant-based diets may be particularly helpful for both prevention and treatment of fatty liver disease. Clinical trials have not yet studied low-fat, high-fiber vegetarian diets for this disease. However, these diets typically cause weight loss and can lower the levels of blood fats (e.g., triglycerides) that contribute to nonalcoholic fatty liver disease. Such diets are also associated with reduced insulin resistance and greater antioxidant protection, compared with meat-based diets.
Alcohol avoidance: Alcohol intake can raise blood triglyceride concentrations, which are elevated in a majority of individuals with nonalcoholic fatty liver disease. Consumption of more than 40 grams of alcohol per day doubles the risk of fatty liver and other liver diseases. Women may be affected at even lower levels of intake (e.g., 20 to 30 grams a day).
Antioxidants: Some evidence suggests a role for dietary antioxidants. Oxidative stress, which is the imbalance between potentially harmful oxidants and protective antioxidants, occurs in individuals with fatty liver. The result is DNA damage, alterations in proteins, destruction of cell membranes, and inflammation. However, clinical trials have yet to be performed to determine the benefit of dietary or supplemental antioxidants in the prevention or treatment of this disease.