Background

Roux-en-Y gastric bypass (RYGB) and one anastomosis gastric bypass (OAGB) represent two of the most used laparoscopic bariatric/metabolic procedures (BMS). The metabolic and physiological consequences shape the short- and long-term outcomes of bypass surgeries, and the variations in the gut microbiota (GM) composition, currently understated, may be a possible key driver.

Methods

Prospective, cohort, multicenter study enrolling patients with severe obesity, randomized between OAGB or RYGB. Fecal and blood samples were collected, pre- (T0) and 12 months postoperatively (T1). ObjectsTo evaluate and compare OAGB vs RYGB microbiota profile shift at 1 year and its impact on metabolic and nutritional status.

Results

An overall significant variation was detected in anthropometric and serum nutritional parameters at 1 year, and no differences were found in total weight loss (TWL) and body mass index (BMI) among the two groups. Whereas GM composition at 1 year showed a significant decrease in overall microbial diversity, with an increase in relative abundances of Actinobacteria and Proteobacteria and a reduction of Bacteroidetes, while no significant changes were observed in Firmicutes and Verrucomicrobia. Yet, we observed an increase of the Firmicutes/Bacteroidetes (F/B) ratio following bariatric surgery, related to the surgical procedure.

Conclusions

BMS promotes a dramatic change in GM composition one year postoperatively. This is the first RCT evaluating the impact of omega vs Roux-Y bypass on GM profile. The bypass technique per se did not impact differently on GM, with similar effect on weight loss and comorbidities resolution/improvement.