Novel Targetable BIOmarkers in ANorexia NervosA

N=8 adult male and female patients with confirmed diagnosis of anorexia nervosa restrictive type, non-exercising subtype Inclusion criteria: * Age 18-60 years * Written informed consent * BMI 10-16 kg/m2 N=8 adult male and female patients with confirmed diagnosis of anorexia nervosa restrictive type, exercising subtype will be included in this study. Inclusion criteria: * Age 18-60 years * Written informed consent * BMI 10-16 kg/m2 N=16 control participants, sex- and age-matched to the individual anorexia nervosa patients. Inclusion criteria: * Age 18-60 years * Written informed consent * BMI 19-24.9 kg/m2 Exclusion Criteria: * Use of antibiotics within the last 31 days * Current illicit drug abuse including daily marijuana or CBD (cannabidiol) consumption (≤ 24 g of alcohol per day allowed) * Any kind of severe chronic disease other than AN (e.g. active cancer disease) * Severe renal impairment (e.g. estimated glomerular filtration rate \<30 ml/min/m2) if resulting from another disease than AN * Known liver cirrhosis or other severe liver impairment if resulting from another disease than AN * Acute upper respiratory tract infection within the last 31 days * Uncontrolled dysthyroidism * Uncontrolled hypertension * Current pregnancy/lactation or current treatment for in vitro fertilization * Inability to understand the study information, to sign the consent form and to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc.