Visceral Adiposity, Vagal Tone and Food Preferences: a Pilot Study

Adiposité Viscérale, Tonus Vagal Et Préférences Alimentaires : Une Étude Pilote

Food preferences are defined by a number of measurable parameters, such as per se food choices, sensitivity of taste and olfactory sensory perceptions, hedonic appreciation of foods ("liking") and motivation to consume them ("wanting"). These food preferences are fundamental to the quality of food intake, and are therefore a key factor influencing weight loss or maintenance of a stable weight. Obesity is also associated with reduced sensory sensitivity to taste and smell, as well as disturbances in the responses of the food reward system.

However, the internal, or physiological, mechanisms impacting these food preferences are still poorly understood. To date, several studies seem to point to the role of body composition, in particular visceral adiposity, or adiposity surrounding the digestive organs. Indeed, a high level of visceral adiposity is associated with the onset of numerous cardiometabolic disorders, but also with altered sensory perceptions.

This relationship could be mediated by the vagus nerve, which connects the digestive organs to the brain, enabling the perception of internal signals sent by the body, such as feelings of hunger or satiety. Low vagal activity is associated not only with abdominal obesity, but also with reduced sensory sensitivity to taste and smell, and changes in food choices in favor of energy-dense foods (rich in fats and/or sugars). Electrical stimulation of the vagus nerve is now recognized as a possible treatment for morbid obesity in the USA, but the mechanisms leading to the expected weight loss are still debated. Similarly, an increase in vagal tone has been found in patients who have undergone bariatric surgery for the treatment of severe complicated to morbid obesity, in parallel with sensory disturbances.

The overall aim of this project is to explore and confirm the relationship between visceral adiposity and various food preference parameters, such as olfactory and gustatory perceptions and reward system responses, involving liking and wanting certain foods and associated behaviors. This project also aims to shed light on the possible mediation of the vagus nerve in this relationship.

Inclusion Criteria:

• Have a BMI between 18.5 and 35 kg/m²;
• French-speaking;
• Be able to travel to the Research Center of the Institut Universitaire de Cardiologie et Pneumologie de Québec for an investigative visit.

Exclusion Criteria:

• Smokers ;
• Women who know they are pregnant, breastfeeding or menopausal;
• Who have been diagnosed with type I or type II diabetes;
• Having undergone bariatric surgery or obesity medication (GLP1 analogue, naltrexon-bupropion combination, etc.);
• Presenting an allergy or intolerance to one of the products used in the sensory tests (taste test: sucrose, sodium chloride, citric acid, quinine hydrochloride dihydrate; olfactory test: citrus, lemongrass, cinnamon, mint, peppermint, banana, anise, turpentine, garlic, coffee, apple, clove, pineapple, rose, geranium, eucalyptus, wormwood, fennel, caraway, leather, n-butanol, linalool, pyridine, diethyl phthalate, propylene glycol);
• Have a history of pathologies which, in the investigator's opinion, could interfere with the study criteria, such as ENT, neurological, upper digestive or cardiac pathologies;
• Receiving long-term pharmacological treatment, in particular antidepressants, antipsychotics, benzodiazepines, beta-blockers, etc. ;
• Presenting or having presented in the last 6 months a thymic episode such as depression, bipolar disorder, etc. ;
• Wearing a cardiostimulator (pacemaker);
• Minors or adults under guardianship.