SENSILINS: Impact of Cephalic Phase Insulin Release Induced by an Environmental Food Odor Stimulus on Glucose Homeostasis According to Insulin Sensitivity Level

NCT07638111 | Not Yet Recruiting

• 1 other identifier: 69HCL25_1107
• Study Type: interventional
• Target: 20
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Obesity & Overweight; Insulin Resistance Syndrome

Keywords

Glucose Homeostasis; Cephalic Phase Insulin Release; Food odor; Olfaction; Oral glucose tolerance test; Insulin secretion; GLP-1

Outcome Measures

Primary Outcomes (1)

• Within-subject difference in glucose incremental area under the curve (iAUC) from 0 to 120 minutes during OGTT

  Primary endpoint is the mean within-subject difference between food odor and control conditions in glucose incremental area under the curve from 0 to 120 minutes after oral glucose ingestion. Glucose iAUC will be calculated using the trapezoidal method, baseline-adjusted to glucose at T0. The main analysis will also assess the interaction between condition (odor vs control) and metabolic status (no overweight/insulin-sensitive vs obesity with low-to-moderate insulin resistance). Unit should be specified in the statistical analysis plan according to assay reporting (for example mmol/L×min or mg/dL×min).

  During each experimental visit, from 0 to 120 minutes after ingestion of the 75 g oral glucose load

Secondary Outcomes (37)

• Preabsorptive and early post-ingestion insulin iAUC as a measure of cephalic phase insulin release

  From pre-OGTT odor exposure through 15 minutes after glucose ingestion during each experimental visit

• Preabsorptive and early post-ingestion C-peptide iAUC

  From pre-OGTT odor exposure through 15 minutes after glucose ingestion during each experimental visit

• Glycemic kinetic response during OGTT - Δmax

  From 0 to 120 minutes after glucose ingestion during each experimental visit

• Glycemic kinetic response during OGTT - Time to peak

  From 0 to 120 minutes after glucose ingestion during each experimental visit

• Glycemic kinetic response during OGTT - Growth curve slope

  From 0 to 120 minutes after glucose ingestion during each experimental visit

Study Arms (2)

Food Odor Stimulation

ACTIVE COMPARATOR

Participants are exposed to a pleasant appetitive food odor delivered through a ScentRealm collar beginning 10 minutes before ingestion of a 75 g oral glucose load and continuing according to a prerecorded sequence during the metabolic test visit.

Behavioral: Pleasant Food Odor Stimulation; Behavioral: Control Environmental Condition

Control Condition

PLACEBO COMPARATOR

Participants undergo the same standardized metabolic test visit and OGTT procedures in the same test environment without food odor stimulation.

Behavioral: Pleasant Food Odor Stimulation; Behavioral: Control Environmental Condition

Interventions

Pleasant Food Odor Stimulation BEHAVIORAL

Exposure to an experimentally selected appetitive food odor (madeleine odor) delivered using a programmable ScentRealm collar in a standardized test room beginning at T-10 minutes before OGTT.

Control Condition; Food Odor Stimulation

Control Environmental Condition BEHAVIORAL

Standardized testing environment identical to the experimental visit but without diffusion of the appetitive food odor.

Control Condition; Food Odor Stimulation

Eligibility Criteria

• Age: 18 Years - 50 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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
• Able to understand study information, read and write French, and provide written informed consent
• Affiliated with a social security scheme or equivalent
• Non-smoker and non-vaper
• Willing not to take dietary supplements, probiotics, prebiotics, or laxatives for 10 days before each visit
• For women of childbearing potential: negative serum pregnancy test; not pregnant and not breastfeeding
• ETOC flash olfactory screening: able to detect the odor-containing vial among 4 presented vials for all 7 odors tested
• Able to identify the madeleine odor used in the study
• Rated pleasantness/appetence of the madeleine odor above 1/9
• For the no-overweight group: BMI 19 to \<25 kg/m² and HOMA-IR \<1.7
• For the obesity group: BMI 30 to \<35 kg/m² and low-to-moderate insulin resistance based on HOMA-IR \[protocol inconsistency to resolve; see note below\]

You may not qualify if:

• 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
• Legal protection measure (guardianship/curatorship)
• Deprivation of liberty by judicial or administrative decision
• Exceeded annual compensation limit for research participation
• Lack of valid required health documentation in the event of exceptional governmental epidemic measures
• Limited venous access making repeated blood sampling/catheter placement difficult
• Current or permanent anosmia or olfactory disorder
• Type 1 or type 2 diabetes, treated or untreated
• History of gestational diabetes
• Known or treated hypertension
• Blood pressure \>160 \[unit missing; likely mmHg systolic threshold\]
• Dyslipidemia, treated or untreated
• Triglycerides \>3 mmol/L
• Allergic rhinitis

Sponsors & Collaborators

• Hospices Civils de Lyon: lead

Study Sites (1)

Centre de Recherche en Nutrition Humaine Rhône-Alpes, Centre Hospitalier Lyon Sud

Pierre-Bénite, 69495, France

Location

MeSH Terms

Conditions

Obesity; Overweight; Metabolic Syndrome; Anosmia

Condition Hierarchy (Ancestors)

Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases; Body Weight; Signs and Symptoms; Pathological Conditions, Signs and Symptoms; Insulin Resistance; Hyperinsulinism; Glucose Metabolism Disorders; Metabolic Diseases; Olfaction Disorders; Sensation Disorders; Neurologic Manifestations; Nervous System Diseases

Central Study Contacts

Anne Laure MD CASTELL, Dr

CONTACT

+33 4 78 86 19 72; anne-laure.castell@chu-lyon.fr

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: PARTICIPANT
• Masking Details: Participants are not informed before study completion that the difference between the two test visits concerns the olfactory environment. The test room, staff interaction rules, music, and visual setting are standardized across visits to minimize expectancy effects.
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: Two-period, two-sequence crossover study (AB/BA) comparing food odor stimulation versus control condition during an OGTT. Randomization is stratified by sex and metabolic group, with restricted permuted blocks of variable size. The washout period between study periods is 4 weeks (±3 days).

Study Record Dates

• First Submitted: March 19, 2026
• First Posted: June 10, 2026
• Study Start: June 1, 2026
• Primary Completion (Estimated): July 1, 2027
• Study Completion (Estimated): July 1, 2027
• Last Updated: June 10, 2026

Record last verified: 2026-06

Locations

FR (1)