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

Score of the Gastrointestinal Symptom Rating Scale assessed upon admission and discharge (two time points), in relation to the predominant dietary pattern (>80% during the rehabilitation phase), defined as flexitarian, vegetarian, or vegan and body weight development. The Gastrointestinal Symptom Rating Scale is a validated questionnaire : Svedlund J, Sjödin I, Dotevall G. GSRS--a clinical rating scale for gastrointestinal symptoms in patients with irritable bowel syndrome and peptic ulcer disease. Dig Dis Sci. (1988) 33(2):129-34. doi: 10.1007/BF01535722. The primary outcome is analyzed seperately for patients with anorexia nervosa and bulimia nervosa.

The Gastrointestinal Symptom Rating Scale is assessed weekly during inpatient treament.

Dietary intake is closely monitored from the beginning to the end of the inpatients stay. The data of the plans will be summarized weekly, containing information on the intake of macro- and micronutrients, fibre, energy intake and food groups. The outcome is analyzed seperately for patients with anorexia nervosa and bulimia nervosa.

Body weight in kg is measured in underwear in the morning before breakfast using a calibrated scale in order to calculate the Body mass index or body mass index z-score. The outcome is analyzed seperately for patients with anorexia nervosa and bulimia nervosa.

Body height in cm is measured using a standardized stadiometer to calculate the body mass index or the body mass index z-score. The outcome is analyzed seperately for patients with anorexia nervosa and bulimia nervosa.

Body composition is measured with bioelectrical impedance

Eating Disorder Inventory-2 (EDI-2): A 91-item self-report questionnaire assessing psychological and behavioral traits related to eating disorders across 11 subscales. Each item is scored from 0 to 2; total scores range from 0 to 182, with higher scores indicating worse outcomes (greater symptom severity. Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

This is a self-report measure of eating behavior with 51 items across three subscales: Cognitive Restraint, Disinhibition, and Hunger. Items are primarily dichotomous (yes/no), with some Likert-scale items. Subscale scores vary in range, and the total score ranges from 0 to 51, with higher scores indicating worse outcomes (e.g., more disinhibited eating, greater hunger, or excessive restraint). Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

Symptom-Checklist-90-Revised (SCL-90-R): A 90-item self-report questionnaire assessing general psychological distress across 9 symptom dimensions (e.g., depression, anxiety, somatization) and 3 global indices. Each item is rated from 0 (not at all) to 4 (extremely). Total scores range from 0 to 360, with higher scores indicating worse psychological symptom severity. Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

This is a 21-item self-report questionnaire assessing the severity of depressive symptoms over the past two weeks. Each item is rated on a scale from 0 to 3. Total scores range from 0 to 63, with higher scores indicating worse depressive symptom severity. Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

This is an 18-item self-report questionnaire measuring the severity of obsessive-compulsive symptoms across 6 subscales (e.g., washing, checking, hoarding). Each item is rated from 0 (not at all) to 4 (extremely). Total scores range from 0 to 72, with higher scores indicating worse obsessive-compulsive symptom severity. Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

This is a 7-item self-report questionnaire assessing symptoms of generalized anxiety over the past two weeks. Each item is rated from 0 (not at all) to 3 (nearly every day). Total scores range from 0 to 21, with higher scores indicating worse anxiety symptom severity. Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

This is a 25-item self-report questionnaire assessing retrospective childhood symptoms of ADHD in adults. Each item is rated from 0 (not at all or never) to 4 (very much or very often). Total scores range from 0 to 100, with higher scores indicating greater severity of ADHD-related childhood symptoms. Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

This is a 24-item self-report questionnaire measuring the presence of subclinical autistic traits in adults. Each item is rated from 0 (strongly disagree) to 3 (strongly agree). Total scores range from 0 to 72, with higher scores indicating more pronounced subthreshold autistic traits.Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

This is a 35-item self-report questionnaire assessing perfectionism across multiple dimensions, including concern over mistakes, personal standards, and parental expectations. Each item is rated from 1 (strongly disagree) to 5 (strongly agree). Total scores range from 35 to 175, with higher scores indicating greater levels of perfectionism. Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

This is a self-report instrument assessing subjective experiences of stress over the past weeks. The standard version includes 30 items, each rated on a scale from 1 (almost never) to 4 (usually). Total scores range from 30 to 120, with higher scores indicating greater perceived stress. Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

Age is assessed by documenting the birth date (day, months, year) from the health insurance card.

Complete Blood Count (CBC) with Differential: A standard laboratory test used to assess general health and detect hematological abnormalities. Measures include red blood cells, white blood cells, hemoglobin, hematocrit, platelets, and a differential count of white blood cell subtypes (neutrophils, lymphocytes, monocytes, eosinophils, basophils). Results outside reference ranges may indicate infection, anemia, inflammation, or immune response abnormalities. Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

A standard blood chemistry panel measuring key electrolytes involved in fluid balance, neuromuscular function, and metabolic regulation.

Sodium (Na⁺): typically 135-145 mmol/L

Potassium (K⁺): typically 3.5-5.0 mmol/L

Chloride (Cl-): typically 98-107 mmol/L

Magnesium (Mg²⁺): typically 0.7-1.0 mmol/L

Phosphate (PO₄³-): typically 0.8-1.5 mmol/L Abnormal values may indicate renal dysfunction, metabolic imbalance, or effects of medications. Higher or lower levels indicate worse physiological regulation depending on the parameter. Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

This Liver Function Panel (ALT, AST, GGT, ALP, Bilirubin, Albumin, INR) is a comprehensive blood test panel assessing hepatocellular injury and liver synthetic function.

Alanine aminotransferase (ALT): < 50 U/L

Aspartate aminotransferase (AST): < 50 U/L

Gamma-glutamyl transferase (GGT): < 60 U/L

Alkaline phosphatase (ALP): 35-125 U/L

Total Bilirubin: 0.3-1.2 mg/dL

Albumin: 3.5-5.0 g/dL

International Normalized Ratio (INR): 0.9-1.2 Elevated enzyme levels may indicate hepatocellular injury or cholestasis, while changes in bilirubin, albumin, or INR reflect impaired liver function. Deviations from normal values indicate worsening liver status, depending on the parameter. Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

This Renal Function Panel (Creatinine, Urea/BUN, eGFR) is a standard blood test panel assessing kidney function and glomerular filtration.

Serum Creatinine: typically 0.6-1.3 mg/dL

Blood Urea Nitrogen (BUN)/Urea: typically 7-20 mg/dL (or 2.5-7.1 mmol/L)

Estimated Glomerular Filtration Rate (eGFR): > 90 mL/min/1.73 m² (normal) Abnormal values may indicate impaired renal function, dehydration, or nephrotoxic effects. Higher creatinine or BUN and lower eGFR indicate worse kidney function. Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.

Self-reported and/or medically verified use of prescribed or over-the-counter medications during the study period, with a focus on agents affecting gastrointestinal physiology. Values are recorded categorically (e.g., no medication, antidepressants, antipsychotics, anxiolytics, GI-active drugs, other). Data are analyzed separately for patients with anorexia nervosa and bulimia nervosa.