Effect of GLP1 Receptor Agonist on Brain Insulin Responsiveness

Inclusion Criteria: * BMI between 18.5 and 24.9 kg/m2; and between 27.5 kg/m2 and 40 kg/m2 * Written consent to participate in the study * Written consent to be informed about incidental findings Exclusion Criteria: * Type 1 or type 2 diabetes, LADA, MODY, or cardiovascular diseases such as chronic heart failure, myocardial infarction, status post stroke * BMI \< 18.5 or \> 40 kg/m2 * Persons who cannot legally give consent * Pregnancy or lactation * History of severe mental or somatic disorders including neurological diseases (incl. epileptic seizures) * Taking psychotropic drugs * Chronic diseases or medication that influence glucose metabolism * Regular use of analgesic drugs * Previous bariatric surgery * Known allergy against one or more of the used agents * Acute infection and/or antibiotic treatment within the last 4 weeks * Hemoglobin values less than 10.5 g/dl for women, less than 11.5 g/dl for men * Other diseases that in the opinion of the investigator may jeopardize the success of the study or indicate a risk to the volunteer * Participation in a lifestyle intervention study or a pharmaceutical study within the last 30 days * Metal implants which cannot be removed as pacemakers, artificial heart valve, electrical devices as insulin pumps, large tattoos, retainer over more than 4 teeth, contraceptive coil, implanted magnetic metal parts as screws or plates after a surgery * Persons with claustrophobia * Persons with tinnitus * Weight loss or gain of \>5% in the last 3 months * Pancreatic diseases * History or family history of multiple endocrine neoplasia (MEN2) or medullary thyroid cancer * History of malignant thyroid disease * History of malignant disease in the past 5 years * Surgery in the last three months * Chronic tobacco use of more than 10 cigarettes/day * Women who do not consent to refrain from breastfeeding until 2 months after the end of the study * Women of childbearing age who do not consent to use safe method of contraception from 28 days before until 2 months after the end of the study or refrain from heterosexual intercourse during this time * Women of childbearing age who do not consent to take a pregnancy test