In this preliminary short-term study it is investigated, whether a short olfactory stimulation with distinct odours impacts energy expenditure in patients with obesity and lean patients.

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