Oral and gut microbiota features associated with weight-loss outcomes after metabolic and bariatric surgery: a pilot study.

Authors

Ahmed Alwali, Louise B Thingholm, Corinna Bang, Jan Henrik Beckmann, Susanne Sebens, Malte Rühlemann, Matthias Laudes, Clemens Schafmayer, Andre Franke, Mark Philipp, Witigo von Schönfels

Published in

Clinical nutrition ESPEN. Pages 105025. Aug 12, 2026. Epub Aug 12, 2026.

Abstract

Metabolic and bariatric surgery (MBS) is an effective treatment for severe obesity, yet postoperative weight loss outcomes vary considerably between patients. With the relevance of the gut microbiome for obesity, it is of interest to understand the potential role of the oral and gut microbiota for the outcome of MBS. This pilot, hypothesis-generating study aimed to investigate associations between microbiota features and postoperative weight loss outcomes after MBS, assessed by percentage excess weight loss (EWL).
In this pilot study, microbiota profiles from multiple body sites were analyzed in 33 patients undergoing MBS. Stool, oral swab, serum, and adipose tissue samples were collected at the time of surgery; stool and oral samples were collected again six months postoperatively. Microbiota diversity and composition were assessed using 16S rRNA gene sequencing and related to EWL and metabolic outcomes. Bacterial DNA in adipose tissue and serum was explored as an indirect marker of microbial translocation.
Higher diversity of the oral microbiota before surgery was associated with greater postoperative EWL. Stool microbiota diversity increased after surgery and was positively associated with EWL, suggesting postoperative recovery of the gut microbiota in patients with better weight loss outcomes. At the taxonomic level, higher postoperative abundance of Alistipes was observed in stool of patients achieving the greatest EWL, while for the oral cavity at time of operation, Veillonella, a bacteria considered largely beneficial in the oral cavity, was found to be positively associated with response. Community-level analyses of bacterial profiles in subcutaneous fat samples taken at time of MBS showed associations with both EWL (R² = 0.097, p = 0.006) and BMI (R² = 0.055, p = 0.017), whereas no associations were observed for visceral fat or serum. Findings related to individual bacterial taxa and extraintestinal compartments should be interpreted cautiously due to the exploratory nature of the analyses.
This exploratory pilot study suggests that oral and gut microbiota features may be associated with weight loss outcomes after metabolic and bariatric surgery. Future studies are required for validation in larger, procedure-specific cohorts with adjustment for clinical confounders.

PMID:
42586481
Bibliographic data and abstract were imported from PubMed on 13 Aug 2026.

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