Development of a Non-invasive Method for Quantifying Cerebral Glucose Metabolism for Studying the Effect of Glucagon in Humans

Inclusion Criteria: * Capable of understanding the participant information and signing the consent form * Between 25 and 70 years of age * Body mass index \<= 25 kg/m\^2 Exclusion Criteria: * Enrolment in other research project that might interfere with the study * Diabetes diagnosis * Pregnancy or breastfeeding * Use of medications which, in the opinion of the investigator, may jeopardise participant's safety or compliance with the protocol * Diagnosis of psychiatric disorders, dementias, or any other neurological disorders that in the opinion of the investigator precludes compliance with the study protocol, evaluation of the results or represents an unacceptable risk for the participants safety * Severe claustrophobia * Cardiac problems including any of the following: 1. Classified as being in New York Heart Association (NYHA) class III or IV 2. Angina pectoris (chest pain) within the last 6 months 3. Acute myocardial infarction (heart attack) within last 2 years * Inadequately treated blood pressure at screening defined as repeated resting blood pressure outside the range 90-150 mmHg for systolic and 50-100 mmHg for diastolic. * Active or recent malignant disease * Current or history of severe alcohol use or drug/chemical abuse as per investigator's judgement * Any chronic disorders or severe diseases which, in the opinion of the investigator, might jeopardise participant's safety or compliance with the protocol