Fecal Microbiota Transplant for Anorexia Nervosa

Anorexia nervosa (AN) is one of the most treatment-resistant psychiatric disorders, with high relapse rates and limited effective biological interventions. Emerging research suggests that people with AN harbor a distinctly altered gut microbiome — reduced diversity, shifted community structure — which may perpetuate the illness through gut-brain signaling pathways that influence appetite, mood, and metabolism. This pilot randomized controlled trial, based at Hamilton Health Sciences Corporation (expected to begin recruiting around May 2026), will test whether Fecal Microbiota Transplant (FMT) — transferring stool from healthy donors into AN patients — is feasible and acceptable as a treatment approach. Participants will be randomized to receive either FMT or a placebo procedure, with researchers tracking changes in body weight, gut microbiome composition, urine and blood biomarkers, and mood symptoms. The core hypothesis is that reshaping the gut microbial community toward a healthier profile could help restore normal appetite regulation and reduce psychiatric symptoms. Because this is a pilot trial, the primary goal is to establish whether the approach is safe enough and well-tolerated enough to justify a larger definitive trial. If successful, this would represent a genuinely novel biological treatment angle for a condition that desperately needs new options.

• This is a not-yet-recruiting trial (status as of source date); no efficacy or safety results are available — all findings listed here reflect the study's pre-specified aims rather than observed outcomes.
• The trial is designed to assess feasibility and acceptability of FMT as primary endpoints, with preliminary effectiveness (weight change, microbiome engraftment, biomarker shifts, mood symptoms) as secondary exploratory endpoints.
• The study will generate multi-omic mechanistic data (gut microbiome sequencing, urine metabolomics, blood biomarkers) alongside clinical outcomes, enabling hypothesis generation about which microbial or metabolic features mediate any observed treatment signal.

This is a pilot randomized controlled trial (RCT) comparing FMT versus placebo in patients diagnosed with anorexia nervosa, conducted by Hamilton Health Sciences Corporation. Specific sample size has not been disclosed in the available abstract, consistent with a pilot feasibility design. The intervention is FMT (route and donor-selection protocol not yet specified in the public record), with outcome measures spanning body weight, gut microbiome composition, urine and blood biomarkers, and mood symptom ratings. Follow-up duration is not reported in the current registration; methods details are best-effort extrapolations from the abstract and should be treated as low-confidence pending full protocol publication.

Because this is a pilot trial, it is explicitly not powered to detect definitive efficacy; any positive signals will require replication in a larger, adequately powered RCT before clinical conclusions can be drawn. The study design does not yet disclose donor-selection criteria, FMT delivery route, or blinding strategy for the placebo arm — each of which substantially affects engraftment success and interpretation of results. Potential confounders specific to AN (severe malnutrition altering gut transit time and mucosal integrity, concurrent refeeding protocols, psychiatric comorbidities, and medication use) may limit the generalizability of microbiome engraftment findings to less medically compromised patients. The next critical experiment would be a fully powered multicenter RCT with standardized donor screening, longer-term follow-up (≥12 months), and mechanistic sub-studies linking specific microbial taxa or metabolites to clinical response.

This trial extends the broader FMT-in-non-CDI-indications framework visible across the corpus: it parallels [§74], which investigates gut microbiome manipulation as a therapeutic lever in a psychiatric condition (antipsychotic-naive schizophrenia), reinforcing the emerging paradigm that gut-brain axis dysbiosis is a tractable target across psychiatric diagnoses. It also parallels [§72], which examines microbiota remodeling and metabolic outcomes after bariatric surgery — a population that, like AN, involves extreme alterations in body weight and gut ecology — though the mechanistic direction is reversed (weight gain vs. weight loss) and the intervention is pharmacological-microbial rather than surgical. The study's multi-omic endpoint design (metagenomics, metabolomics, blood biomarkers) situates it alongside [§86], which uses deep metagenomic sequencing to link gut microbiota and metabolome signatures to a neurological outcome (post-stroke cognitive impairment), providing a methodological comparator for how integrated microbiome-metabolome profiling can uncover mechanistic pathways. More broadly, the trial addresses the translational question foregrounded by [§100] — whether microbiome findings can move from ecological description to causal intervention — placing it at the frontier of the corpus's central tension between associative and mechanistic evidence.

• Gut Microbiome in AP Naive
  Both use gut microbiome manipulation as a therapeutic strategy in a psychiatric condition, making this the most direct design-level comparator; contrasting findings across AN versus schizophrenia populations could reveal whether microbiota-based interventions have disorder-specific or transdiagnostic mechanisms.
• Microbiota remodeling after bariatric surgery: Procedure-specific dynamics and metabolic implications
  Bariatric surgery produces dramatic microbiota remodeling alongside weight change — the inverse metabolic trajectory to AN — making this a useful natural-experiment comparator to understand whether shared microbial taxa drive weight normalization regardless of the direction of the intervention.
• The human microbiome at translational crossroads: an ecological and causal perspective
  This conceptual article directly addresses the causal-versus-associative challenge in microbiome research; reading it alongside this FMT trial clarifies what inferential claims a pilot RCT design can and cannot support regarding gut-brain causality in AN.
• Integrated gut microbiota and metabolome signatures revealed by deep metagenomic sequencing in post-stroke cognitive impairment with type 2 diabetes
  Employs a comparable integrated metagenomics-plus-metabolomics endpoint strategy in a neuropsychiatric context (post-stroke cognition), offering a methodological benchmark for how multi-omic microbiome data should be analyzed and interpreted when the primary outcome is brain-related.
• Gut microbiota-modulating interventions in paediatric type 1 diabetes: a systematic review and meta-analysis
  A systematic review and meta-analysis of gut microbiota-modulating interventions in a pediatric chronic condition (type 1 diabetes) provides the highest available level of evidence for what microbiome intervention trials can realistically achieve, contextualizing the effect sizes this pilot trial should aim to detect in a future powered study.