Brown Adipose Tissue as Nutrient Buffer Through Diet Induced Thermogenesis

Inclusion Criteria: * BMI 18.5 to 28 kg/m2 * Able to give informed consent as documented by signature Exclusion Criteria: * Concomitant medication other than prescription free analgesics (paracetamol and NSAID) and oral contraceptives * Other clinically significant concomitant disease states (e.g., renal failure, hepatic dysfunction, cardiovascular disease, diabetes mellitus) * Hyper- or hypothyroidism * Smoker / habitual tobacco use * Weight change of \>5% within 3 months prior to inclusion * Hypersensitivity to cold (e.g. Raynaud syndrome) * Known or suspected non-compliance, drug or alcohol abuse * Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. of the participant * Enrolment of the investigator, his/her family members, employees and other dependent persons * Enrolment into another study using ionizing radiation within the previous 12 months * Enrolment into another study including a pharmacological or nutritional intervention * Pregnancy or lactation * Lab parameters * Serum-Creatinine: above 1.5x upper limit of normal (ULN) * Glycated Hemoglobin (HbA1c): above 6.0% * Random plasma glucose \>11 mM