Development of Gastrointestinal Symptoms in Patients With Anorexia Nervosa and Bulimia Nervosa During Weight Rehabilitation Over Time, Depending on the Nutritional Strategy

This prospective observational study investigates the development of gastrointestinal (GI) symptoms in patients with anorexia nervosa (AN) and bulimia nervosa (BN) during multi-week inpatient weight rehabilitation. The study explores how the predominant nutritional strategy-flexitarian, vegetarian, or vegan-relates to changes in GI symptoms over the course of treatment. In addition to diet, the study examines how weight gain and other clinical, psychological, and demographic factors influence the trajectory of GI symptoms. Patients complete weekly questionnaires assessing GI symptoms as part of routine care at the Eating Disorder Center of the Klinik Lüneburger Heide, Germany. Further data are drawn from standard clinical assessments, including body weight, body composition, and psychometric instruments. The primary outcome is the change in GI symptom severity (measured via the GSRS score) from admission to discharge, analyzed in relation to dietary pattern and weight development. Secondary analyses will explore symptom progression over time, group differences between AN and BN, and predictors of GI symptom improvement, including dietary intake, baseline psychological status, symptom change, weight trajectory, and treatment duration. The study aims to recruit approximately 150 patients with AN and 35-40 with BN. Inclusion requires a diagnosis of AN (any subtype) or BN, age over 12 years, clinical stability, and the ability to provide informed consent. The findings aim to inform evidence-based dietary recommendations for individuals with eating disorders who experience significant GI symptoms during nutritional rehabilitation.

• Gastrointestinal Symptoms in the Timecourse [Time frame: Data are continuously collected from admission to discharge. Extraction occurs on the first three days of admission, weekly during the stay (on Mondays or Tuesdays, covering the preceding week), and on the final three days of discharge.]
• Dietary intake [Time frame: Data are continuously collected throughout the inpatient stay. Extraction takes place on the day of admission, weekly during the stay (on Mondays or Tuesdays, reflecting the data of the preceding week), and on the day of discharge.]
• Body weight [Time frame: Data are continuously collected from admission to discharge. Extraction occurs the second day in the morning after admission, weekly during the stay (on Mondays or Tuesdays), and at the day of discharge]
• Body height [Time frame: Body weight is measured within the first two days after admission and again within the final two days prior to discharge. For inpatient stays exceeding three months, weight measurements are repeated at three-month intervals.]
• Body composition [Time frame: Body composition is measured within the first two days after admission and again within the final two days prior to discharge. The outcome is analyzed seperately for patients with anorexia nervosa and bulimia nervosa.]
• Eating Disorder Inventory-2 (EDI-2) [Time frame: Data are collected within the first three days after admission and during the final three days before discharge (two time points).]
• Three Factor Eating Questionnaire (TFEQ) [Time frame: Data are collected within the first three days after admission and during the final three days before discharge (two time points).]
• Symptom-Checkliste (SCL-90-R) [Time frame: Data are collected within the first three days after admission and during the final three days before discharge (two time points).]
• Beck-Depressions-Inventar Revision (BDI-II) [Time frame: Data are collected within the first three days after admission and during the final three days before discharge (two time points).]
• Obsessive Compulsive Inventory - Revised (OCI-R) [Time frame: Data are collected within the first three days after admission and during the final three days before discharge (two time points).]
• Generalizied Anxiety Disorder Scale-7 (GAD-7) [Time frame: Data are collected within the first three days after admission and during the final three days before discharge (two time points).]
• Wender Utah Rating Scale (WURS-K) [Time frame: Data are collected within the first three days after admission and during the final three days before discharge (two time points).]