Donor-derived microbial engraftment and gut microbiota shifts associated with weight loss following fecal microbiota transplantation (Jun 2025, n=23) "52% achieved weight loss of more than 5% from baseline. Average weight loss of 8kg/18lbs" FMT

[Michael Harrop]

https://journals.asm.org/doi/10.1128/aem.00120-25

Chinese study. 52% achieved weight loss of more than 5% from baseline. Average weight loss of 8kg (18 lbs). Nonresponders lost 3kg.

Contrary to some other studies, they found engraftment to correlate with success.

ABSTRACT​

Fecal microbiota transplantation (FMT) is a promising treatment for microbiota dysbiosis and may provide metabolic benefits for obesity. However, its mechanisms and variability in clinical outcomes remain poorly understood.

This 12-week multicenter, single-arm study evaluated the efficacy of FMT for weight loss and explored the role of donor-derived microbial engraftment and functional shifts in mediating weight loss among overweight and obese individuals.

Twenty-three participants (body mass index ≥24 kg/m²) without diabetes received three biweekly FMT sessions via a nasojejunal tube. Fecal samples from participants and donors were analyzed using metagenomic sequencing.

By week 12, 52% of participants were classified as responders, achieving significant weight loss of ≥5% from baseline, with an average weight loss of 7.98 ± 2.69 kg (P < 0.001). In contrast, non-responders lost 2.90 ± 1.89 kg (P < 0.001). Responders exhibited a significantly higher proportion of donor-derived microbial strains post-FMT compared to non-responders (37.8% vs 15.2%, P = 0.020). Notably, key taxa, including Phascolarctobacterium (P = 0.034) and Acidaminococcaceae (P = 0.012), increased significantly in abundance in responders post-FMT, indicating successful microbial engraftment as a critical determinant of therapeutic success.

These findings suggest that FMT is a viable intervention for weight loss in obese individuals. Successful donor-derived microbial engraftment strongly correlates with weight loss efficacy, highlighting the potential of microbiota-targeted therapies in obesity management and providing insights into the mechanisms underlying FMT outcomes.

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IMPORTANCE​

Prior research indicates that fecal microbiota transplantation (FMT) is a promising treatment for diseases related to microbiota imbalance, potentially providing metabolic benefits for obesity. However, the specific role of donor-derived microbial engraftment in driving clinical efficacy has remained unclear. In this study, we evaluated the efficacy of FMT in promoting weight loss and explored the role of donor-derived bacterial strains in this process. Our findings demonstrate that the successful engraftment of specific donor-derived taxa, such as Phascolarctobacterium and Acidaminococcaceae, is strongly associated with significant weight loss. This highlights the critical interplay between donor microbiota and recipient gut environment. These findings underscore the potential of microbiota-targeted therapies as a novel strategy for obesity management.

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Donors:​

recipients with the same donor tended to have similar weight-loss outcomes, suggesting that donor characteristics may play a role in therapeutic variability

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But they couldn't figure out what donor characteristics were responsible.

25 participants received fresh fecal flora fluids from 10 healthy donors. Each participant underwent three FMT sessions and administered biweekly, and adverse events were monitored throughout the study.

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Donor selection and preparation of FMT solution

Donors aged ≥14 years with a BMI between 18.5 and 23.9 kg/m2 underwent comprehensive screening, including medical history, physical examination, and laboratory testing for infectious and metabolic diseases. Recent antibiotic use or gastrointestinal infections within 3 months were exclusion criteria (15). Fresh stool samples were diluted in sterile physiological saline, homogenized, filtered, and centrifuged to isolate bacterial pellets. These pellets were resuspended in saline containing 12.5% glycerol as a cryoprotectant (27, 28). All steps were performed under strict anaerobic conditions to preserve anaerobes. The final product was stored at −80°C until use (11).

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