Fecal Microbiota Transplantation in Females With Anorexia Nervosa

The goal of this clinical trial is to learn whether fecal microbiota transplantation (FMT) can change the gut microbiome and improve health outcomes in females with anorexia nervosa. FMT involves transferring microorganisms from the stool of a carefully screened healthy donor to the intestine of another person. In this study, FMT will be given as capsules that are swallowed by the participants. The main questions the study aims to answer are: * Does repeated treatment with FMT change the gut microbiome in females with anorexia nervosa? * Does FMT improve symptoms and other health outcomes related to anorexia nervosa? * How does FMT affect gastrointestinal function, including bowel habits and gut transit time in females with anorexia nervosa? * What medical problems or side effects do the participants experience during the study? Researchers will compare FMT capsules with placebo capsules to see whether FMT affects the gut microbiome, gastrointestinal function, and symptoms related to anorexia nervosa. Placebo capsules are similar to the FMT capsules but do not contain donor fecal material. Participants will: * Receive five weekly FMT treatments and five weekly placebo treatments * Be randomly assigned to receive either FMT followed by placebo or placebo followed by FMT * Attend four study visits for clinical assessments and follow-up * Provide stool and blood samples at the study visits * Complete questionnaires about eating disorder symptoms, gastrointestinal symptoms, and general health * Provide information about bowel habits and other aspects of gastrointestinal function Neither the participants nor the study staff will know which treatment is being given during each treatment period. The study will include females aged 15 years or older with anorexia nervosa. The study will help researchers better understand the relationship between the gut microbiome and anorexia nervosa and whether changing the gut microbiome with FMT could potentially be a future treatment approach.