The impact of bariatric surgery on liver enzymes in people with obesity: A 5-year observational study

Background and purpose: Non-alcoholic fatty liver disease (NAFLD) has increasing worldwide prevalence, fuelled by rising obesity rates, and weight reduction is the mainstay of its management. We sought to study the effect of bariatric surgery, the most effective long-term treatment for obesity and associated metabolic disorders, on liver function in people with obesity. Methods: We performed a retrospective longitudinal cohort study of 511 patients who had undergone bariatric surgery (71 sleeve gastrectomy and 440 gastric bypass) over 60 months of follow-up. Patients were stratified into groups based on their baseline alanine aminotransferase (ALT) into Group A (ALT < 40 U/L) and Group B (ALT > 40 U/L). Postoperative follow-up weight loss, liver function tests, HbA1c, blood pressure and lipid profiles were collected. Findings: Bariatric surgery resulted in nadir total weight loss of 33.1% by 24 months (p < 0.001) with no significant difference between groups. In people with raised baseline ALT (Group B), ALT and gamma glutamyl transferase (GGT) levels decreased significantly by 4 months postoperatively (p < 0.001) and sustained over 60 months of follow-up. There was also significant and sustained reduction in HbA1c, blood pressure, total cholesterol, and non-HDL cholesterol overall with no differences between groups. Conclusions: Bariatric surgery results in significant weight loss, improves liver function tests and metabolic outcomes in people with obesity. Bariatric surgery could be a therapeutic consideration for patients with NAFLD associated with severe obesity who have otherwise been unresponsive to conservative management.