Nonalcoholic fatty liver is defined as hepatic steatosis in the absence of alcohol use or another chronic liver disease. It is one of the most common liver diseases, affecting approximately 15 million persons in the United States. Persons who weigh more than 140 percent of their ideal body weight are at increased risk of developing nonalcoholic fatty liver disease. In addition, persons with diabetes mellitus and hyperlipidemia are more likely to have nonalcoholic fatty liver disease. Because of these associations, weight reduction was assumed to be an effective treatment for overweight patients with nonalcoholic fatty liver disease. Wang and colleagues evaluated the literature to assess the evidence supporting the efficacy of weight reduction in the treatment of nonalcoholic fatty liver disease.

The authors performed an extensive search for relevant studies through computerized databases (including the Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Controlled Trials Register, MEDLINE, and EMBASE). They also conducted a manual search of abstracts from various scientific meetings. Included were studies that reported histology of the liver, serum transaminase levels, or radiologic imaging of the liver in obese patients who lost weight. Various weight reduction methods included diet, exercise, drug therapy, surgical interventions, or any combination. Studies were excluded if the weight-loss surgical intervention was jejunoileal or small-bowel bypass procedures.

Of the 517 potentially relevant trials identified, 15 met the inclusion criteria. One was a randomized controlled trial, two were non-randomized controlled trials, nine were case series, one was a retrospective review, and two were case reports. Nine of the studies had 25 or fewer participants, while three studies included more than 50 participants. Twelve studies used behavior, dietary, or pharmacotherapeutic interventions, while three studies used surgical intervention. All of the studies reported overall improvements in outcome measures such as serum transaminase levels, radiologic markers, or hepatic histology. In one study, liver histology worsened in patients who lost more than 1.6 kg (3 lb, 8 oz) per week. In one of the surgical interventions, there was a twofold increase in the number of patients who developed lobular hepatitis after surgery.

The authors conclude that even though weight reduction is considered an effective therapy for nonalcoholic fatty liver, few data support or refute this recommendation. They add that there is a need for randomized controlled trials to determine whether weight reduction in these patients is beneficial. This fact is important because nonalcoholic fatty liver disease is an emerging public health problem.