The Effects of One Anastomosis Gastric Bypass Surgery on the Gastrointestinal Tract

Nutrients. 2022 Jan 12;14(2):304. doi: 10.3390/nu14020304.


One anastomosis gastric bypass (OAGB) is an emerging bariatric procedure, yet data on its effect on the gastrointestinal tract are lacking. This study sought to evaluate the incidence of small-intestinal bacterial overgrowth (SIBO) following OAGB; explore its effect on nutritional, gastrointestinal, and weight outcomes; and assess post-OABG occurrence of pancreatic exocrine insufficiency (PEI) and altered gut microbiota composition. A prospective pilot cohort study of patients who underwent primary-OAGB surgery is here reported. The pre-surgical and 6-months-post-surgery measurements included anthropometrics, glucose breath-tests, biochemical tests, gastrointestinal symptoms, quality-of-life, dietary intake, and fecal sample collection. Thirty-two patients (50% females, 44.5 ± 12.3 years) participated in this study, and 29 attended the 6-month follow-up visit. The mean excess weight loss at 6 months post-OAGB was 67.8 ± 21.2%. The glucose breath-test was negative in all pre-surgery and positive in 37.0% at 6 months (p = 0.004). Positive glucose breath-test was associated with lower reported dietary intake and folate levels and higher vitamin A deficiency rates (p ≤ 0.036). Fecal elastase-1 test (FE1) was negative for all pre-surgery and positive in 26.1% at 6 months (p = 0.500). Both alpha and beta diversity decreased at 6 months post-surgery compared to pre-surgery (p ≤ 0.026). Relatively high incidences of SIBO and PEI were observed at 6 months post-OAGB, which may explain some gastrointestinal symptoms and nutritional deficiencies.

Keywords: gastric bypass; gut microbiota; pancreatic exocrine insufficiency; small-intestinal bacterial overgrowth.

Publication types

  • Evaluation Study

MeSH terms

  • Adult
  • Blind Loop Syndrome / etiology*
  • Exocrine Pancreatic Insufficiency / etiology*
  • Female
  • Gastric Bypass / adverse effects*
  • Gastric Bypass / methods
  • Gastrointestinal Microbiome
  • Gastrointestinal Tract / microbiology
  • Gastrointestinal Tract / physiopathology
  • Humans
  • Intestine, Small / microbiology
  • Male
  • Malnutrition / etiology*
  • Middle Aged
  • Obesity, Morbid / microbiology
  • Obesity, Morbid / surgery
  • Pilot Projects
  • Postoperative Complications / etiology*
  • Prospective Studies
  • Treatment Outcome
  • Weight Loss