Fecal Microbiota Transplantation (FMT) in Treatment of Severe and Enduring Anorexia Nervosa

Inclusion Criteria: * Provision of signed and dated informed consent form. * Stated willingness to comply with all study procedures and availability for the duration of the study. * Female aged 18-45. * Diagnosed with SE-AN, defined here as having suffered from AN for five or more years and having participated in two or more inpatient or residential treatment programs followed by weight relapse. * Sufficiently medically stable to receive FMT (serum electrolytes within normal limits, normal EKG) * Willing to adhere to the FMT dosing regimen. * For females of reproductive potential, in sexual relationships with men, must use an acceptable method of contraception from 30 days prior to enrollment until 4 weeks after completing study treatment.\* Participants must also be willing to be subjected to periodic pregnancy tests. * Agreement to adhere to Lifestyle Considerations throughout study duration. * Adequate insurance to cover inpatient stay. * Lifestyle Considerations: During this study, participants are asked to: * Participate in standard inpatient treatment at UNC-Chapel Hill's CEED. * Remain nil per os (npo) on the morning of each dosing session and for two hours after receiving FMT, on four individual instances of FMT administration. * Abstain from sexual activity or use a condom or other form of highly effective birth control during the 30-day active stage of the clinical trial. * Inform the research team as soon as possible if they become pregnant during the eight-week and six-month follow-up periods. * If a trial participant has begun a course of one of this trial's prohibited medications during the eight-week or six-month follow-up periods, participants will be asked only to report the name of the medication, dose, and duration of treatment. Exclusion Criteria: * Male or outside of the 18-45 range * Previous FMT or microbiome-based products at any time excluding this study * Patients with allergies to ingredients Generally Recognized As Safe (GRAS) * Patients with a history of severe anaphylactic or anaphylactoid food allergy * Patient received antibiotics in the last 48 hours. Patients will be eligible to enroll if antibiotic therapy is discontinued for at minimum 48 hours prior to start of study * Requires continued antibiotic use or anticipates antibiotic use in the upcoming 4 weeks * Concurrent intensive induction chemotherapy, radiation therapy, or biological treatment for active malignancy. * Pregnancy or lactation * Febrile illness within past month * Treatment with another investigational drug within the past month * Alcohol or drug dependence either at time of the study or within the last year * Active gastrointestinal infection at time of enrollment * Any gastrointestinal or potentially intestinal microbiota-related conditions, including: Severe gastroparesis (e.g., gastric pacemaker) and any history of gastrointestinal illness (including but not limited to inflammatory bowel disease, irritable bowel syndrome, celiac disease, any gastrointestinal cancer, etc.) * Major gastrointestinal surgery (e.g. significant bowel resection) within 3 months before enrollment. This does not include appendectomy or cholecystectomy * Type 1 or 2 diabetes mellitus * Known or suspected toxic megacolon and/or known small bowel ileus * History of total colectomy or bariatric surgery * Solid organ transplant recipients less than or equal to 90 days posttransplant or on active treatment for rejection * If at risk for CMV/EBV associated disease (at investigator's discretion, e.g. immunocompromised), negative IgG testing for cytomegalovirus (CMV) or Epstein-Barr Virus (EBV). * Patients who are immunocompromised * Unable or unwilling to comply with protocol requirements * Expected life expectancy \< 6 months * A condition that would jeopardize the safety or rights of the subject, would make it unlikely for the subject to complete the study, or would confound the results of the study