Mastication and Energy Expenditure in Normal Weight and Obese People

A group of 12 subjects presenting a normal weight and a group of 12 obese subjects, with a good general health and a good dental state will be constituted. They will participate to 5 different recording sessions during which they will be invited to chew and spit out foods and chewing gums of different hardness. During recording sessions with mastication and no‐mastication periods, gas exchange (O2 concentration), cardiac activity (electrocardiography) and muscular activity of masticatory muscles (electromyography) will be recorded. Blood samples will be collected during one of the sessions to analyse the kinetic of appearance of some hormones in the blood compartment during or just after mastication. The selected hormones are involved in the eating behaviour and its regulation (ghrelin, peptide C, peptide YY and glucose‐like peptide 1). From these recordings, energy expenditure, heart rate variability, intensity of masticatory muscle contraction, and hormone blood appearance will be analysed in link with the nature and hardness of the food chewed. Since the food bolus is spit out after mastication (without any swallowing = sham‐feeding), the changes observed in theses variables will be directly attributed to sensory information coming from oral cavity during mastication. Food choice and sport activity of each volunteer will be taken into account to compare the results obtained for the two groups (normal weight and obese). The work will produce more data and evidence on the contribution of oral signals attributable to the food in the regulation of the energy balance. The results will also bring more knowledge on the involvement of the autonomic nervous system. Comparison of the results obtained for the two groups (normal weight and obese people), will bring some positive outcomes which could be useful in the fight against obesity.