American Society of Metabolic and Bariatric Surgery review of gut microbiome and alterations related to weight loss treatment, by the Clinical Issues Committee

The gut microbiome is a critical mediator of metabolic health including obesity and type 2 diabetes. Microbial composition variation - driven by diet, genetics, environment, and host physiology - can influence insulin sensitivity, energy absorption, fat storage, and systemic inflammation. Metabolic and bariatric surgery (MBS) is associated with distinct shifts in gut microbiota that may contribute to weight loss and metabolic improvements. Changes in microbial diversity, bile acid metabolism, and enrichment of beneficial taxa have all been linked to favorable metabolic outcomes. Furthermore, the gut microbiome may interact with molecular signaling pathways including glucagon-like peptide-1 signaling. Despite probiotics and prebiotics showing potential modulation of the gut microbiota, their clinical impact on obesity management remains inconsistent. Understanding the complex interplay between MBS, the gut microbiome, and host metabolism may offer novel insights into future therapeutic targets. As the field advances, microbiome-based strategies may enhance procedure selection, improve patient outcomes after MBS, and contribute to more personalized, durable treatment approaches for obesity and its related diseases.

Published by Surgery for obesity and related diseases : official journal of the American Society for Bariatric Surgery, 2026. The guideline itself is at the source linked here.

doi.org/10.1016/j.soard.2025.11.021