Effects of Bariatric Surgery on Liver Function Tests in Patients with Nonalcoholic Fatty Liver Disease

Objectives: Nonalcoholic fatty liver disease (NAFLD) affects over 80% of obese patients and is fueled by the metabolic syndrome. Weight loss is strongly advocated as a central treatment for NAFLD and has been shown to induce histological improvement. We aimed to define the patterns of improvement in NAFLD with weight loss and determine target weight goals for NAFLD resolution. Methods: A prospective study of 84 morbidly obese patients with NAFLD undergoing bariatric surgery was conducted. Intraoperative liver biopsies were taken. Monthly follow-up, including blood tests and measurements, was performed. We monitored improvements in NAFLD by monthly alanine aminotransferase (ALT) and gamma glutamyltransferase (GGT) levels over 1 year. Results: There was rapid improvement in ALT, particularly in the first 6 months following surgery, with statistically significant reduction in ALT at 2 months (35 vs 27 IU/L, p < 0.001). In multivariate analysis, there were significantly increased odds of ALT normalization after a %TBWL of 10–15% (odds ratio 2.49, p = 0.005). The odds of resolution increased with increasing weight loss. Triglyceride levels (odds ratio 0.59, p = 0.021) and baseline NAFLD activity score (odds ratio 0.28, p < 0.001) were also significantly related to ALT normalization. Improvements in ALT occurred prior to metabolic improvement and well before traditional ideal weight goals were reached. Conclusion: Improvements in NAFLD occurred rapidly after bariatric surgery and were closely related to weight loss and metabolic factors. A 10–15% reduction in body weight is an appropriate target to achieve substantial improvement in ALT levels. Trial registration number: Australian Clinical Trials Registry (ACTRN12610000049077).