A Study on the Effects of Combined FMT on Gut Microbiota and Eating Disorder Symptoms in AN

The goal of this clinical trial is to determine if Fecal Microbiota Transplantation (FMT) is effective in treating Anorexia Nervosa (AN). The study will also explore how FMT works. The main questions it aims to answer are: 1. What is the efficacy of combined FMT treatment in patients with AN? 2. What is the relationship between treatment efficacy and changes in gut microbiota, and what mechanisms underlie the effects of FMT in treating AN? Researchers will compare FMT to a placebo (a look-alike substance that contains no active ingredients) to see if FMT is effective in treating AN. Participants will: * Be hospitalized * Take FMT or placebo daily for 6 days * Provide stool and blood samples before and after FMT * Visit the clinic every 4 weeks for check-ups and tests