Gut Microbiota Modifications and Weight Regain in Morbidly Obese Women After Roux-en-Y Gastric Bypass

Introduction The relationship between late post-bariatric surgery weight regain and gut microbiota is not completely understood. Objective To analyze the profile of gut microbiota among patients with and without late weight regain after post-Roux-en-Y gastric bypass (RYGB) and to compare it with a control group (CG) comprised of obese Brazilian individuals. Methods This is a cross-sectional study which enrolled 34 morbidly obese women divided into 3 groups: post-Roux-en-Y gastric bypass without (RYGB_non-regain), and with weight regain (RYGB_regain) at least 5 years after surgery, and a CG of preoperative individuals. Gut microbiota was determined by metagenomic analyses. Results The alpha diversity was higher in groups RYGB non-regain and RYGB regain when compared with CG (p < 0.05). Both RYGB non-regain and RYGB regain groups showed a lower abundance of the phylum Bacteroidetes when compared with CG (p < 0.01). The genera Bacteroides and SMB53 were increased in CG (p < 0.05). Group RYGB non-regain showed more abundance of the Akkermansia genus when compared with CG and group RYGB regain (p < 0.05). RYGB non-regain showed a greater abundance of the Phascolarctobacterium genus and lower of the SMB53 genus when compared with CG (p < 0.05). RYGB non-regain showed a greater abundance of the Phascolarctobacterium genus and a lower of the SMB53 genus when compared with CG (p < 0.05). Conclusion The gut microbiota of individuals which presented late weight regain after RYGB was significantly different in comparison to individuals with a successful weight loss, a finding that points towards a significant role of gut microbiota on weight loss and maintenance after surgery.