Donor-derived microbial engraftment and gut microbiota shifts associated with weight loss following fecal microbiota transplantation.

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 ( < 0.001). In contrast, non-responders lost 2.90 ± 1.89 kg ( < 0.001). Responders exhibited a significantly higher proportion of donor-derived microbial strains post-FMT compared to non-responders (37.8% vs 15.2%, = 0.020). Notably, key taxa, including ( = 0.034) and ( = 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.IMPORTANCEPrior 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 and , 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.CLINICAL TRIALSThis study is registered with the Chinese Clinical Trial Registry as ChiCTR1900024760.