Impact of Olfactory Odour StimulatioN on Energy EXpenditure

Inclusion Criteria: * • Age 18-55 years * Obesity (BMI ≥30 kg/m2) and Lean (BMI 18-25 kg/m2) * Written informed consent * Normosmia (defined by sniffing Sticks test) Exclusion Criteria: * • Chronic or acute sinusitis * Surgical intervention of the nasal cavity or the paranasal sinus * Known allergy to odors used in the study * Smokers * Current illicit drug abuse including daily marijuana and cannabidiol (CBD) consumption (alcohol ≤2 drinks per day allowed) * Any kind of severe chronic disease (e.g. severe heart failure, active cancer disease) * Diabetes mellitus * Treatment with insulin sensitizing drugs including Glucagon-like Peptide (GLP)-1 analogues within the last 3 months * History of neurodegenerative diseases, severe head trauma * Severe renal impairment (e.g. estimated glomerular filtration rate \<30 ml/min/m2) * Known liver cirrhosis or other severe liver impairment * Use of any kind of decongestant more than twice a week * Use of cortisone-containing nasal spray within the last 3 months * Acute upper respiratory tract infection * Uncontrolled dysthyroidism * Uncontrolled hypertension * Regular use of psychopharmaceutic drugs * Study participants aims to start a new diet or exercise program during the study * Bariatric surgery * Pregnancy/Lactation * Onset of climacteric symptoms within one year (e.g. hot flashes and/or diaphoresis) OR initiation of hormonal replacement therapy in the last three months * Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. * Participation in an interventional study within the last 3 months