Gut Microbiota Responses to Bariatric Surgery Are Associated with Metabolic Outcomes and Type 2 Diabetes Remission

Bariatric surgeries, such as Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), improve obesity and type 2 diabetes (T2D). Both surgeries affect the gut microbiota, but their contribution to T2D remission remains unclear. In this subanalysis (RYGB, n = 39; SG, n = 38) of the randomized controlled Oseberg trial ( NCT01778738 ), in which participants underwent either RYGB or SG surgery, we profiled the faecal microbiome of individuals with obesity and T2D before and 12 months after surgery. We show that both surgeries altered the microbiome in the same direction, but with larger changes after RYGB. The SG-associated altered microbiome composition correlated positively with circulating glucagon-like peptide 1 levels, beta-cell function and 5 year T2D remission. Remission was also linked to increased gene richness and metabolic potential for fermentation, methanogenesis and butyrate production. Notably, these associations persisted after accounting for the extent of weight loss. Our findings indicate that surgery-specific microbial adaptations influence metabolic improvements and may help to explain heterogeneity in T2D remission after bariatric surgery.