Fecal Microbiota Transplant for Anorexia Nervosa

The purpose of this pilot randomized-controlled trial is to determine whether Fecal Microbiota Transplant (FMT) treatment demonstrates feasibility, acceptability, and prelinary effectiveness among patients with anorexia nervosa (AN). Specifically, the investigators aim to compare changes in weight, gut microbiome, urine, blood biomarkers and mood symptoms between participants receiving the FMT intervention and placebo.

In the following pilot randomized-controlled trial, the investigators' aim is to determine whether FMT treatment demonstrates feasibility, acceptability, and preliminary effectiveness in pediatric AN participants. The investigators will assess how the use of FMT affects participants' rate of weight restoration, gut microbiome, relevant urine and blood biomarkers, and mood symptoms. The investigators' rationale for performing the study is to better understand the interactions between the intestinal microbiome, energy regulation, and behavior. This will be the first study to assess the role of FMT in pediatric AN and will help establish whether this adjunctive treatment modality has benefit in managing the metabolic and behavioral manifestations of this complex neuropsychiatric disorder.

In terms of study procedures, members of a pilot sample of 20 AN patients recruited from McMaster Children's Hospital will be randomized to receive FMT or placebo. All participants will be asked to complete a battery of assessments at regular intervals over the 8-week intervention period, and at a follow-up point at four weeks post-intervention.

The study's primary outcomes are recruitment and retention rates. Descriptive statistics will be used to determine the number of adolescents who will agree to participate in the study and those who will complete the study.

One of the study's secondary outcomes is participants' attitudes toward FMT. This will be measured through qualitative interviews among those who completed the intervention and those who do not agree to participate in the study.

The investigators will know we have reached saturation by using a method called "information power" and will explore how broad the research questions are, if there are clear theories to guide the analysis, how varied the participants in the study are, and how much useful information is accrued. Based on this, the investigators will determine the appropriate number of interviews to lead.

The remaining secondary outcome is a battery of preliminary outcomes (clinical, biological, biochemical and safety). The investigators will assess these outcomes at multiple timepoints using questionnaires, anthropometric data, stool analysis (16s rRNA), urine metabolic analysis, saliva ultra filtrates, changes in blood work, and common terminology criteria for adverse events for safety outcomes.

Eligibility Criteria:
Inclusion Criteria: All study subjects will have been diagnosed with AN (restricting type or binge eating/purging type) by the primary physician on the ED team, as per standard approach. Study participants will:

* Be 12-17 years-old at time of recruitment
* Have capacity to consent
* Be assigned female sex at birth (may be gender diverse)
* Be active patients in the pediatric ED program at MCH
* Have a weight that is \<85% of the Treatment Goal Weight, as determined by the treating physician

Exclusion Criteria: Potential study subjects will be excluded due to the following reasons:

* Exposure to antibiotics within two weeks of study randomization
* Initiation of new probiotics / oral nutritional supplements within two weeks of randomization
* Active pregnancy
* Active psychosis or suicidal ideation
* Other comorbidities that may affect weight or the gut microbiome including celiac disease, inflammatory bowel disease (or other conditions as determined by the study team)