Guan B, Chen Y, Chong TH, et al. - Patients receiving Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) were examined for their serum enzyme status and for the related predictors. From January 2013 to January 2018, they included 500 patients (201 RYGB, 299 SG) in this retrospective review. Bariatric surgery candidates commonly exhibit serum enzyme abnormalities; prevalence of abnormalities reduces postoperatively. Reduction in alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyltranspeptidase (γ-GT), adenosine deaminase, cholinesterase, lactic dehydrogenase (LDH), creatine kinase, and hydroxybutyrate dehydrogenase (HBDH) levels and an increase in amylase and superoxide dismutase levels were observed in correlation with undergoing RYGB and SG. Observations suggest independent predictive value of age and preoperative γ-GT level for ALT, AST, γ-GT, and LDH change 1 year postoperatively. Postoperative change could be predicted with preoperative ALT, AST, ALP, LDH, and HBDH levels, respectively. A possible predictive value of gender and surgical procedure for postoperative ALP change was suggested.