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Indian Journal of Gastroenterology

12-04-2025 | Respiratory Microbiota | Systematic review

Impact of bariatric surgery on gut microbiota in obese patients: A systematic review

Authors: Nima Mohammadzadeh, Shabnam Razavi, Mahla Shahriari, Gholamhossein Ebrahimipour

Published in: Indian Journal of Gastroenterology

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Abstract

Background

Obesity is a multi-factorial disease linked to various metabolic disorders, including insulin resistance, type-2 diabetes (T2D) and cardiovascular diseases. Traditional treatments often show limited long-term success, while bariatric surgery has emerged as the most effective intervention for sustained weight loss and comorbidity improvement. Alterations in gut microbiota may significantly contribute to these metabolic improvements.

Objective

This systematic review was aimed at evaluating changes in gut microbiota composition before and after bariatric surgery and their association with clinical outcomes, including weight loss, insulin sensitivity and lipid metabolism.

Methods

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a comprehensive search of PubMed, Scopus, Web of Science and clinicaltrials.gov databases was conducted for studies published between 2004 and 2024. Keywords included “bariatric surgery,” “gut microbiota” and “obesity.” Inclusion criteria focused on human studies with pre and post-surgical microbiota analysis. Non-human studies, pediatric populations and studies without microbiota assessment were excluded. Data extraction covered microbiota profiles, metabolic outcomes and clinical markers.

Results

Total 27 articles and 28 clinical trials met the inclusion criteria. Pre-surgery, obese patients exhibited dysbiosis characterized by reduced microbial diversity and imbalances in key bacterial phyla. Post-surgery, especially after Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), patients showed increased microbial diversity, reduced Firmicutes and elevated beneficial bacteria such as Akkermansia muciniphila and short-chain fatty acid (SCFA) producing bacteria. These microbiota changes were correlated with significant improvements in weight loss, insulin sensitivity and lipid profiles. However, some studies reported inconsistent or modest microbiota changes.

Conclusion

Bariatric surgery leads to significant gut microbiota alterations that are closely linked to metabolic improvements, including enhanced glucose control and lipid metabolism. However, the long-term sustainability of these microbial changes remains unclear. Longitudinal studies are essential to determine whether these alterations persist over time and how they continuously impact metabolic health. Further research should explore targeted microbiota interventions to maintain beneficial microbial profiles post-surgery.

Graphical Abstract

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Metadata
Title
Impact of bariatric surgery on gut microbiota in obese patients: A systematic review
Authors
Nima Mohammadzadeh
Shabnam Razavi
Mahla Shahriari
Gholamhossein Ebrahimipour
Publication date
12-04-2025
Publisher
Springer India
Published in
Indian Journal of Gastroenterology
Print ISSN: 0254-8860
Electronic ISSN: 0975-0711
DOI
https://doi.org/10.1007/s12664-025-01763-x

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