Abstract
Anorexia nervosa (AN) is a severe mental disorder characterized by restrictive eating and disturbance in the way one’s body weight or shape is experienced, often accompanied by depression and anxiety. Current evidence-based treatments for AN have limited efficacy, with less than half of the patients achieving full recovery in long-term follow-up studies. Recent findings have identified gut microbiota (GM) dysbiosis as a potential contributor to AN pathology through the gut-brain axis. This open-label, non-randomized, feasibility trial (Clinicaltrials.gov Identifier: NCT05834010) evaluated the feasibility of utilizing fecal microbiota transplantation (FMT) to modify the GM and GM-associated signaling in females with AN and to examine biological effects following a single FMT procedure. Adult female participants diagnosed with AN were recruited. FMT was administered either orally via capsules or as rectal enema. Stool and blood samples were collected pre- and one week post-FMT to assess GM composition, hormonal changes, and biomarkers. Primary endpoints: Feasibility of FMT in individuals with AN and preferred route of FMT. Secondary endpoints: A single FMT treatment can alter GM composition in individuals with AN short term and relevant gut brain signaling in serum. 18/22 participants (81%) completed FMT and sampling and 19/22 participants chose oral capsules, with no serious adverse effects reported. GM analysis showed significant shifts toward donor composition 1-week post-FMT, with improved stool consistency. No significant changes were observed in psychopathology measures or appetite-related biomarkers. Oral FMT is a feasible intervention for adult women with AN, leading to changes in GM profile. Future studies should focus on placebo-controlled trials to assess the efficacy of repeated oral treatments and explore long-term effects on GM, appetite, body weight, sex hormones, disorder-specific symptoms, and overall well-being
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Data availability
The metagenomic sequencing data generated in this study have been deposited in the NCBI Sequence Read Archive under accession number PRJNA1184021. De-identified biological data and study materials are available from the corresponding author upon reasonable request for up to five years after publication. The study protocol and analytic code are provided in the Supplementary Files. Individual participant data cannot be shared due to the Danish Data Protection Act, which supplements the EU General Data Protection Regulation (GDPR), but aggregated data are available as described or upon request. All study documents and materials are stored in accordance with the Act on Processing of Personal Data and relevant provisions of the Danish Health Act governing biobanks. Participants were informed of these protections during the consent process. After analyses, biological samples will be stored in a biobank for 15 years.
Code availability
All custom R scripts used for data processing, statistical analyses, and figure generation (Supplementary data 2) are publicly available at https://github.com/farhadm1990/fmt_trial. A DOI-minted archive of the analysis workflow is available on Zenodo (https://doi.org/10.5281/zenodo.17949926).
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Acknowledgements
Thank you to Dr. Jitka Stilund Hansen, who was an integral part of the ideation process. Lundbeck Foundation (LF-Experiment, R370-2021-863, KKB) funded this study.
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Conceptualization: KKB, MS. Methodology: KKB, HCML,KDR, DSN, MH, FMP. Investigation: RKS, SM, KDR, MH, NM, MAR. Visualization: FMP, MAR. Funding acquisition: KKB, MS. Project administration: KKB. Supervision: KKB. Writing – original draft: FMP, KKB. Writing – review & editing: All authors.
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FMP, RKS, MS, MH, DSN, AMP, SM, KR, MAR, KKB declare no competing interests. HCML declares two international patents: WO 2021/130182 A1 and WO 2024/141422. NM is associate editor for European Eating Disorders review and BJPsych Open and funded by Laureate Grant Award from the Novo Nordisk Foundation (Grant No: NNF22OC0071010).
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Panah, F.M., Støving, R.K., Sjögren, M. et al. Impact of a single fecal microbiome transplantation in adult women with anorexia nervosa: an open-label feasibility pilot trial. Nat Commun (2026). https://doi.org/10.1038/s41467-026-68455-8
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DOI: https://doi.org/10.1038/s41467-026-68455-8


