This single-center, randomized, single-blind, 2-period crossover interventional study will evaluate whether exposure to a pleasant food odor 10 minutes before a 75 g oral glucose tolerance test (OGTT) modifies glucose homeostasis in adults with different metabolic phenotypes. Participants will undergo two experimental conditions in random order: food odor stimulation and control condition without odor, separated by a 4-week washout. The main objective is to quantify the within-subject effect of food odor stimulation on the incremental area under the glucose curve (iAUC) from 0 to 120 minutes during OGTT and to assess whether this effect differs according to metabolic status. Two predefined groups will be enrolled: adults without overweight and without insulin resistance, and adults with class I obesity and low-to-moderate insulin resistance. Secondary objectives include characterization of cephalic phase insulin release (CPIR), C-peptide and GLP-1 responses, glycemic kinetics, associations between CPIR and metabolic responses, and participant acceptability of the test environment and olfactory stimulation. A plasma biobank will be constituted from part of the collected samples for future research.
Age 18 to 50 years inclusive
Stable body weight during the previous 3 months (±5% of total body weight)
Willing to comply with the full study protocol
Sedentary lifestyle or stable regular physical activity, with agreement to keep this unchanged throughout the study
Unstable medical or psychological conditions that could impair compliance, safety, or study participation in the investigator's judgment
Alcohol consumption >30 g/day, or established abuse/dependence on another drug
Ongoing exclusion period from another study listed in the national volunteer file
Legal protection measure (guardianship/curatorship)