Didier Chapelot

Consequence of Omitting or Adding a Meal in Man on Body Composition, Food Intake, and Metabolism

Objective: To investigate in man the consequence on body composition and related biological and metabolic parameters of omitting or adding a meal.

Modalities of the food intake-reducing effect of sibutramine in humans

Sibutramine is a serotonin and noradrenaline reuptake inhibitor exerting a weight reducing effect partly via its anorectic properties. We investigated the effects of 15 mg sibutramine on objective (intake) and subjective (sensations) parameters of eating behavior in 24 young male subjects. At 0830 h subjects took either placebo or sibutramine in a counterbalanced order, followed by a fixed amount of breakfast. Intake was covertly recorded in the laboratory until the dinner meal, and then until the next morning using diary reports. Sibutramine induced a highly significant reduction in energy (1304 kJ, p < 0.001), protein (294 kJ, p < 0.001), fat (414 kJ, p < 0.01), and carbohydrate (CHO, 594 kJ, p < 0.001) intakes compared to placebo. This reduction was further enhanced when 24-h intake was analyzed (1601 kJ, p < 0.001). The effect of sibutramine occurred mainly at lunch (637 kJ, p = 0.005). Throughout the test day the number of items consumed and the weight of food were reduced by sibutramine (1.6, p < 0.01 and 222 g, p < 0.001, respectively), whereas energy density was not changed. Meals minus dessert items were the most altered by sibutramine. A specific CHO reduction was found in the dinner meal, although the proportions of macronutrients in total daily energy intake were not changed by sibutramine. Hunger ratings began to be lower than placebo 240 min after sibutramine. These results show that a single dose of sibutramine in lean humans induces a potent reduction in intake, and that its action is modulated according to the time of occurrence and the structure of the meal.

A role for glucose and insulin preprandial profiles to differentiate meals and snacks.

A physiological distinction between eating occasions may help account for contradictory findings on the role of eating frequency in energy homeostasis. We assessed this issue using a midafternoon eating occasion known in France as the goûter that often consists of snack foods. Among the 24 male subjects, 8 habitually consumed four meals per day, i.e., were usual goûter eaters (GE) and 16 habitually took 3 meals per day, i.e., usual non-goûter non-snack eaters (NGNSE). All subjects were time blinded from lunchtime and had to request subsequent meals. Blood was continuously withdrawn and collected with a change of tube every 10 min until dinner request. During the session, 8 of the non-goûter eaters (NGE) were offered a snack 210 min after lunch and were designated as non-goûter snack eaters (NGSE) if they ate. Results showed that the goûter was preceded by high hunger scores and a linear decline in plasma glucose (-9.0+/-3.0%, P<.05) and insulin concentrations (-22.9+/-6.0%, P<.05). These profiles were not observed before the snack. The dinner of GE was requested later and was smaller compared to NGNSE, whereas the snack altered neither time of request nor energy intake (EI) at dinner. Among blood variables, leptin at the onset of eating was the only factor that was predictive of both intermeal interval and EI. The glucose and insulin profiles indicate that snacks should not be considered as meals in studies on the role of eating frequency in energy homeostasis.

Acute effects of pharmacological modifications of fatty acid metabolism on human satiety.

The role of NEFA in eating behaviour is still poorly known. Our objective was to examine whether etomoxir (ETO), an inhibitor of NEFA oxidation, or ( - )-hydroxycitrate (HCA), an inhibitor of lipogenesis which may indirectly stimulate NEFA oxidation, alters satiety. Post-lunch satiety was measured in eight normal-weight male subjects who were deprived of time cues and received on three occasions either ETO (320 mg), HCA (2 g) or placebo (PLA) in random order. Between lunch and dinner, blood was withdrawn continuously and collected every 10 min for measures of plasma concentrations of glucose, insulin, lactate, TAG, NEFA, beta-hydroxybutyrate (BHB), leptin and ghrelin. Results showed that HCA began to decrease hunger and desire to eat compared to PLA and ETO 210 min after lunch and increased satiety duration compared to PLA by 70 (se 23) min (P < 0.05), but did not modify energy intake at dinner. ETO did not affect any variable of satiety. HCA increased NEFA concentrations during the pre-dinner period, whereas ETO increased and decreased plasma concentrations of NEFA and BHB, respectively. Mean differences in plasma NEFA concentrations between HCA and PLA were predictive of the differences in satiety duration between treatments (r2 0.71, P < 0.01). Among treatments, plasma leptin concentration at dinner onset was the only blood variable correlated with energy intake at this meal (r - 0.75, P < 0.0005). In healthy, normal-weight men, acute HCA increased the intensity and duration of satiety possibly via increased NEFA disposal for oxidation.

Influence of environmental factors on meal intake in overweight and normal-weight male adolescents. A laboratory study☆

OBJECTIVE To investigate the influence of environmental conditions on energy intake at lunch time in normal-weight versus overweight male adolescents. DESIGN Healthy 15-17 year-old adolescents (19 normal-weight, 19 overweight) participated in lunch tests under laboratory settings. Four conditions were compared: eating in groups, eating alone, eating alone while viewing television, eating alone while listening to music. The same menus (two solid foods, three drinks) were offered ad libitum. RESULTS Significant group differences between meal conditions were observed for energy intake from solid foods, but not from drinks: normal-weight participants ate more solids while listening to music (5731±426 kJ) than when eating alone (5012±364 kJ, P=0.026) or in groups (4974±272 kJ, P=0.049), whereas overweight participants ate more solid foods while viewing television (5806±330 kJ) than when eating in groups (5208±201 kJ, P=0.014) or while listening to music (5288±255 kJ, P=0.035). On average, total energy intake at lunch (solids plus liquids) was found to be increased only in the overweight when viewing television (8527±535 kJ) compared to eating in group (7348±445 kJ, P=0.037) or while listening to music (7532±435 kJ, P=0.049). CONCLUSION Environmental conditions modulate total energy intake at lunch in adolescents and susceptibility to external factors can be affected by weight status. Whether such effects can in turn affect energy balance and weight status remains to be investigated.

Heart rate variability and depressed mood in physical education students: A longitudinal study

Autonomic nervous system (ANS) activity, and more specifically its parasympathetic component, has been reported to be associated with depression. The objective of this longitudinal study was to assess whether changes in heart rate variability (HRV) and in depressive moods were interrelated in healthy young subjects. Thirty students in physical education with a high physical load, were followed over the university year at 3 periods: October (P1), February (P2) and May (P3). Depressive mood was assessed by the score on the Depression subscale of the profile of mood state (POMS) questionnaire. HRV was assessed in supine and during an active orthostatic test with total power (TPms(2)) as the sum of the very low (VLF), low (LF) and high frequency (HF) bands, LF/HF ratio representing sympathetic and HFms(2) parasympathetic modulations. Results showed that changes in Depression scores between P1 and P2 were negatively and positively associated with changes in TPms(2), LFms(2), and HFms(2) in supine position and during orthostatism respectively. Although Anger/Aggressivity, Fatigue, and Vigor scores of the POMS were also correlated with changes in some HRV indices, Depression was the only significant predictive factor of changes in TPms(2) and HFms(2) between P1 and P2 in supine position and during orthostatism. These results were not observed between P2 and P3. In conclusion, in a healthy young sample of population, changes in depressive moods are associated with changes in total rhythmical power of HRV and more specifically its parasympathetic component.

Simulated high altitude selectively decreases protein intake and lean mass gain in rats

The aim of this study was to find out whether high altitude (HA)-induced hypophagia was macronutrient-specific using a self-selection procedure. Body composition was assessed by dual X-ray absorptiometry before and after exposure and by dissection at the end of the experiment. Energy intake, macronutrient selection, body composition, plasma insulin and leptin concentrations were measured in rats (FHx) exposed 16 h daily for 10 days to hypobaric hypoxia (HH) simulating an altitude of 5500 m. Rats were fasted during the exposure to HH and had access to food only during the 8 h of normoxia in their active period. This group was compared to control group (C) with ad libitum access to food and a group of rats submitted only to the 16-h fast (FNx). Results showed that sustained hypophagia was specific to protein (55 +/- 5% of C, P < .05), whereas after a decline, carbohydrate intake reached its basal level on the 5th day. HH dramatically reduced fat-free mass gain (P < .05 and P < .0001 compared to C and FNx, respectively). Plasma leptin concentrations at the onset of the period of access to food were not significantly different from those of controls. Across groups, leptin was positively correlated with fat mass (r = .71, P < .001) and negatively with energy intake (r = -.52, P < .05), more specifically with protein intake (r = -.57, P < .05). These results suggest that HA leads to a reduced preference for protein impairing fat-free mass gain and that leptin may contribute to this hypophagia.

Energy compensation after an aerobic exercise session in high-fat/low-fit and low-fat/high-fit young male subjects

There is general agreement that exercise-induced energy expenditure is not entirely compensated for at the next meal or over the following 24 h, but inter-individual variability is high. The role of ‘fatness and fitness’ in this variability has never been assessed. Therefore, eighteen non-obese male subjects aged 22·2 (sd 2·0) years were selected and separated into a ‘high-fatness and low-fitness’ (Hfat/Lfit, n 9) and a ‘low-fatness and high-fitness’ (Lfat/Hfit, n 9) group, according to three criteria: maximal oxygen uptake; weekly hours of physical activity; fat mass index. At 1 h before lunch, they were subjected to 60 min of exercise on a cycle ergometer (70 % VO2max), or stayed at rest. Then, they self-reported food intake in diaries until the next breakfast. Intake at lunch was not different between conditions, but was higher after exercise than after rest over the 24 h, leading to a significant but partial mean level of compensation of 49·8 (sem 16·5) and 37·8 (sem 24·6) % for the Hfat/Lfit and Lfat/Hfit groups, respectively. Energy compensation at lunch and over the 24 h were strongly correlated (r 0·76, P< 0·001). Both groups consumed more fat and protein after exercise than after rest over the 24 h, but the percentage of energy derived from fat increased only in the Hfat/Lfit group (2·1 (sem 0·6) %, P= 0·026). Thus, the energy cost of an aerobic exercise session was partially compensated over the next 24 h independently of the ‘fatness and fitness’ status, but ‘high-fat and low-fit’ individuals compensated more specifically on fats.

Exercise prior to a freely requested meal modifies pre and postprandial glucose profile, substrate oxidation and sympathovagal balance

BackgroundThe effects of exercise on glucose and metabolic events preceding and following a freely initiated meal have never been assessed. Moreover, the relationship between these events and sympathovagal balance is not known. The objective of this study was to determine whether exercise prior to a freely requested meal modifies the pre- and postprandial glucose profile, substrate oxidation and sympathovagal balance.MethodsNine young active male subjects consumed a standard breakfast (2298 ± 357 kJ). After 120 min, they either performed 75 min of exercise on a cycle ergometer (EX - 70% VO2max) or rested (RT). Lunch was freely requested but eaten ad libitum only during the 1st session, and then energy intake was fixed across conditions. Glucose and sympathovagal balance were assessed continuously using a subcutaneous glucose monitoring system and analysis of heart rate variability, respectively. Every 5 min, a mean value was calculated for both glucose and sympathovagal balance. Substrate oxidation was determined by calculating the gas exchange ratio when lunch was requested and 180 min after the onset of eating.ResultsPreprandial glucose profiles were found in 72% of the sessions and with a similar frequency under both conditions. Meals were requested after a similar delay (40 ± 12 and 54 ± 10 min in EX and RT respectively; ns). At meal request, sympathovagal balance was not different between conditions but CHO oxidation was lower and fat oxidation higher in EX than in RT (-46% and +63%, respectively; both p < 0.05). Glucose responses to the meal were higher in incremental (+ 48%) but not in absolute value in EX than in RT, with a higher fat oxidation (+ 46%, p < 0.05), and a greater vagal withdrawal (+ 15%, p < 0.05).ConclusionsThese results show that exercise does not impair preprandial glucose declines at the following meal freely requested, but leads to an increased postprandial glucose response and an elevated fat oxidation, an effect that vagal withdrawal may contribute to explain.

P032 - Biologie du comportement alimentaire : influence de la modification du métabolisme des acides gras

Le rôle du métabolisme des acides gras libres (AGL) dans le comportement alimentaire est mal connu. Il a été montré que les inhibiteurs de l’oxydation lipidique augmentent la prise alimentaire. Nous avons étudié i) si une intervention pharmacologique sur le métabolisme des AGL modifiait le comportement alimentaire spontané chez l’homme et ii) les mécanismes biologiques sous-jacents. Un inhibiteur partiel de l’oxydation des AGL (Etomoxir, ETO, 320 mg), un inhibiteur partiel de la lipogenèse et activateur indirect de l’oxydation des AGL (Hydroxycitrate HCA, 4 g) et un placebo (PLA) ont été administrés à 7 jours d’intervalle à 9 jeunes sujets masculins normo pondéraux. La séquence prandiale spontanée était recréée et un prélèvement sanguin continu effectué [1]. Les quantités consommées au petit déjeuner et au déjeuner étaient déterminées lors de la 1ère session et servies aux autres, le dîner servi en quantité excédentaire à la demande des sujets. Les concentrations plasmatiques de glucose, insuline, AGL, lactate, b-hydroxy-butyrate (BHB), leptine et ghréline étaient mesurées. Sur le plan comportemental, la durée de satiété entre le déjeuner et le dîner était plus longue dans la condition HCA que PLA (+ 77 ± 20 min, P = 0,01) mais non modifiée dans la condition ETO. L’aire sous courbe (ASC) des scores de faim était plus faible dans la condition HCA que PLA (P < 0,005) et ETO (P < 0,05). Les prises énergétiques au dîner ne différaient pas. Sur le plan biologique, l’ASC des BHB plasmatiques était plus faible et celle des AGL plus élevée dans la condition ETO que PLA (respectivement P = 0,01 et P < 0,05), du à l’inhibition de l’oxydation des AGL. Les ASC de glucose, triglycérides, leptine et ghréline plasmatiques étaient plus élevées dans la condition HCA que PLA (P < 0,05) du fait de l’augmentation de la durée de satiété. Ces résultats montrent que l’inhibition partielle de la lipogenèse augmente la satiété mais ne permettent pas d’affirmer un rôle de l’inhibition de l’oxydation des AGL. P033 CALORIMÉTRIE D’EFFORT CHEZ DES TÉMOINS ET DES OBÈSES AVEC OU SANS DIABÈTE : LES PALIERS COURTS DE 3 MIN SOUS-ESTIMENT L’OXYDATION LIPIDIQUE ET SURESTIMENT L’OXYDATION GLUCIDIQUE