Effets de l'activité physique sur l'appétit, l'ingestion alimentaire, l'olfaction et la gustation

Introduction: Overeating, sedentary behaviour and physical inactivity are modifiable and important causes in the development of obesity and related health disorders. It is known that in addition to having beneficial effects on metabolism, exercise increases energy expenditure and helps to maintain the energy balance. Recent studies have shown that exercise may also cause a decrease in caloric intake, leading to better control of the energy balance and may have beneficial health effects, even when practised at low intensity. The objectives of this thesis are to explore the effects of under-studied exercise parameters in weight control by 1) documenting the impact of low to very low intensity tasks (i.e., active workstations) in individuals with excess body weight and on food intake and 2) determining how chemosensory factors related to appetite control are affected by exercise practice relative to rest and in response to various timings of the exercise session.  Methods and results: To address the first research objective, a systematic review was conducted to document the impact of the use of active workstations in individuals with excess body weight (article 1). Nineteen studies were included, of which 12 involved standing workstations, 9 involved treadmill workstations, 3 involved a cycle device, and one involved a stepping device. The results indicate that these workstations are effective in increasing work-hour energy expenditure and reducing sedentary behaviour. An experimental study was conducted to determine the impact of a standing workstation, compared to a conventional sitting workstation, on dietary intake. Thirty-six men and women were randomly assigned to a standing or seated workstation (article 2). They took part in cognitive tasks for about 1h30min on the assigned workstation and were then served an ad libitum snack. The results of the study indicate that there is no significant difference in dietary intake between participants who took part in the sitting condition (427.8 ± 301.8 kcal) and those who were standing (461.2 ± 272.8 kcal; p=0.472). To meet the second objective, we first observed the effect of high-intensity exercise on chemosensory perceptions related to food intake (article 3). Fourteen men took part in random order in two visits consisting of A) a long sedentary break and B) a short sedentary break followed by an exercise session (running at 70% of VO2 max). Upon arrival (8:30), as well as immediately before dinner (11:40), they were subjected to olfactory and taste tests. Then, an ad libitum buffet was served to them at noon. The results showed no significant difference in dietary intake between sedentary and exercise conditions (p=0.888). These results are consistent with the lack of difference in olfactory and gustatory perceptions between conditions (all p >0.05). The concept of timing is relatively new to the field of physical activity and more particularly to the control of the energy balance. The objective of the last project (article 4) was to observe whether the timing of exercise represents a parameter of interest that can optimize the appetite-suppressing effect via chemosensory perceptions. In a protocol similar to article 3, twelve men were subjected in random order to two conditions: A) an exercise session (30 min at 70% of VO2 max) followed by a sedentary break (90 minutes) or B) the sedentary break followed by the exercise session. They took part in olfactory and taste tests upon arrival (8:30 AM) and before the ad libitum dinner (11:40 AM). The results indicate that the timing of the exercise had no impact on olfactory (all p >0.05) and gustatory (all p >0.05) perceptions, or total dietary intake (p=0.459). Conclusion: In conclusion, our work is the first to show that in acute situations the use of a standing workstation does not increase food consumption during a subsequent meal. Moreover, the high-intensity exercise did not result in acute food compensation at the subsequent meal, regardless of the timing of the session. Contrary to the hypotheses put forward, the exercise alone or the timing of the session did not modify olfactory and gustatory perceptions.

Keyphrases: physical activity, anorexigenic effect, taste, smell, active workstation