Hypothalamic GLP-1 Response in Healthy Weight and Obesity

The goal of this clinical trial is to learn how the gut hormone glucagon-like peptide-1 (GLP-1) helps the brain sense sugar. It includes adults with healthy weight and adults with obesity. The main questions this trial aims to answer are: A. Does GLP-1 cause the brain's response to sugar? B. Do lower GLP-1 levels cause a weaker brain response to sugar in adults with obesity? Researchers will compare each participant's brain response across four test days. On these days, GLP-1 levels will be blocked, raised, or left unchanged. Sugar will be given either into the stomach or into a vein. Participants will: Attend 1 screening visit Visit the clinic for 4 test days Receive sugar and get an MRI scan of their brain on each test day

Inclusion Criteria: Group 1: * Age 18-75 years * BMI 18.5-25 kg/m² * Normal glucose tolerance (Fasting glucose \< 5.6 mmol/L) Group 2: * Age and sex-matched with group 1 * BMI≥30 kg/m² * Impaired glucose tolerance (Fasting glucose 5.6 - 6.9 mmol/L) Exclusion Criteria: * Diabetes mellitus type 1 or type 2, or fasting plasma glucose \> 7.0 mmol/L * Treatment with GLP-1 receptor agonists or other GLP-1-based therapies within the past three months * Use of medication affecting appetite, body weight, or glucose metabolism within the past three months * Current eating disorder (anorexia nervosa, bulimia nervosa) * Known serious chronic disease, including but not limited to: * Heart disease * Anemia (hemoglobin \