Weight loss as a treatment for nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease that can progress to cirrhosis and hepatocellular carcinoma. NAFLD has been associated with obesity and other features of the metabolic syndrome, including insulin resistance, impaired glucose tolerance, and dyslipidemia. As a result, and with a lack of other effective treatments, weight loss achieved through lifestyle modifications (diet and exercise) has been promoted as the standard treatment. However, there is very little empiric evidence to support the effectiveness of weight loss for NAFLD. This article reviews the current literature on the effects of weight loss achieved through lifestyle modification or medications on NAFLD. To date, there have been no randomized controlled trials of weight loss interventions on hepatic pathology. Only three published trials (N = 89 subjects), which include a comparison group, have been published. These studies suggest improvement in liver enzymes and/or hepatic pathology; however, direct between group comparisons are lacking. Four small, nonrandomized studies (N = 59 subjects) have evaluated the effect of weight loss achieved with medications (4 of orlistat, 1 of sibutramine) on NAFLD. These suggest some improvement in liver enzymes and histopathology. Finally, a brief review of observational studies on the association between NAFLD pathology or liver enzymes and diet composition suggests a possible role for the manipulation of macronutrients and/or micronutrients in NAFLD treatment. In summary, there is little empiric evidence to support the role of weight loss achieved through lifestyle modification or medication in the treatment of NAFLD. Rigorously conducted, randomized controlled trials are needed in this area.