Introduction Despite its serious impact, anorexia nervosa (AN) remains one of the least understood mental illnesses, with significant gaps in effective treatment options. No medications have been deemed effective and only 50% of individuals respond to conventional psychotherapies. Gastrointestinal (GI) bacteria have been found to be altered in individuals with AN. While, Fecal microbiota transplantation (FMT) has shown potential for alleviating anxiety and depression, its effects remain understudied for individuals with AN. This study aims to determine whether oral capsular FMT is acceptable to adolescents with AN and results in clinical improvement in weight and/or psychological symptoms. Methods This study will randomise 20 adolescents with AN, ages 12–17 years, to receive either FMT or placebo capsules. These 20 youth, as well as an additional 10 youth who decline trial enrolment, will participate in qualitative interviews. We will track recruitment rates and collect psychological and biological measures (blood, stool, urine and saliva) at multiple timepoints to assess how gut microbiota and their metabolites may influence the symptoms of AN. Interviews with participants and caregivers will explore their experiences and views on FMT as a treatment approach. Ethics and dissemination This study has received ethics approval by the Hamilton Integrated Research Ethics Board (#17493) and investigational drug approval by Health Canada (Dossier ID: c292423). Informed consent will be obtained by research staff from all participants. Findings will be disseminated through academic conferences, clinical forums and partnerships with advocacy organisations to reach clinicians, researchers and individuals with lived experience. Trial registration number NCT06593366 .
Couturier et al. (2026) studied this question.