Relative Contribution of Brain Insulin Action for Postprandial Metabolism
The goal of this clinical trial is to clarify (i) the contribution of brain insulin action on regulation of systemic metabolism, (ii) sex-specific differences in the central regulation and (iii) the influence of the menstrual cycle in women.

Therefore, participants will undergo oral glucose tolerance tests combined with a double tracer dilution technique. This approach will be compared between days with insulin delivery to the brain as nasal spray and days with placebo spray.
- EligibilityCriteria: Inclusion Criteria:  BMI < 24 kg/m2 no known primary diseases no hormonal contraception  Exclusion Criteria:  Alcohol or drug abuse Smoking At screening: Hb < 12 g/dl for women and Hb < 14 g/dl for men Any (clinical) condition that would endanger participant's safety or question scientific success according to a physician's opinion. - HealthyVolunteers: Accepts Healthy Volunteers - Gender: All - MinimumAge: 18 Years - MaximumAge: 30 Years - StdAgeList: Adult