Jeanine Louis-Sylvestre

Effects of macronutrient content and energy density of snacks consumed in a satiety state on the onset of the next meal

We examined the effects of nutrient composition of a 1 MJ afternoon snack, consumed in a satiety state, on the spontaneous onset of the next meal in 11 young male subjects deprived of any temporal cues. All subjects attended four experimental sessions scheduled 2 weeks apart. The first, baseline, session served to establish: (1) the subjects ad libitum lunch intake, (2) the latency of the spontaneous request for dinner following lunch, (3) ad libitum food intake at dinner. Lunches provided during the next three sessions were based on baseline lunch intakes. During the following three sessions, conducted in counterbalanced order, subjects were given a high-fat (58% of energy from fat), a high-protein (77%) or a high-carbohydrate (84%) snack to be consumed 240 min after the beginning of lunch. Latency to dinner and the amount of energy consumed at dinner were two dependent variables. Consumption of a high-protein snack delayed the request for dinner by 60 min. In contrast, high-fat snack delayed dinner request by 25 min, whereas high-carbohydrate snack delayed dinner request by 34 min. Snack composition had no impact on energy or macronutrient intakes during dinner.

The Effect of Soup on Satiation

We compared the influence of three solid/liquid preloads to a no-preload condition given at lunchtime on hunger ratings and energy intake of the lunch and subsequent dinner in 12 lean and 10 overweight young men. The preloads (vegetables and water, strained vegetable soup, chunky soup) were of the same composition and volume but differed in distribution of nutrients between the liquid and the solid phases, and in the size of solid particles. Hunger ratings were reduced by the preloads; there was a significantly greater suppression of hunger after the chunky soup than after the vegetables and water. In both groups, the soups reduced energy intake at lunch, although the chunky soup had the most effect. In the overweight subjects, a reduced lunch intake was also followed by a reduced dinner intake. The benefit to weight control of large particles in soup should be evaluated.

Validation of tests of completeness of vagotomy in rats

In recent years there has been renewed interest in the role of the gastrointestinal tract and the abdominal organs in regulating body energy balance. In an attempt to characterize vagal influence, vagotomy has been utilized as a routine manipulation. Recent anatomical findings, behavioral observations and physiological data have led to a re-examination of the validity of the tests usually performed to assess completeness of the operation. In this review, a comprehensive profile of the vagotomized rat is drawn, standard indices are described and discussed and finally, new tests are suggested. It is concluded that, for most of the studies, a set of well-chosen criteria is necessary to ascertain the success of the surgery.

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.

Is Pleasantness of Biscuits and Cakes Related to their Actual or to their Perceived Sugar and Fat Contents

Perceptions of sugar, fat and moisture contents, as well as their influences on pleasantness were investigated in commercial foods. One-hundred-and-two-normal-weight men rated the pleasantness, flavour intensity, moisture, sweetness and fatness of 39 different biscuits and cakes. Sugar content was accurately perceived up to a maximum content of about 33% weight/weight. The perception of fat content was less accurate and depended on both fat and sugar contents. High sugar contents seemed to decrease perception of fatness. Pleasantness was influenced mainly by sugar content and less by fat content. Pleasantness was better predicted by rated contents than by actual contents; it was even better predicted by the overall flavour intensity. Preferences for high fat stimuli did not appear to be based on conscious perception of their fat content. We conclude that the classical results obtained with simple experimental stimuli remain valid, as a first approximation, for commercial biscuits and cakes, despite their complex sensory characteristics.

Influence of PROP-sensitivity on Taste Perceptions and Hedonics in French Women. A Study Performed without Retronasal Olfaction ☆ ☆☆

Detection threshold for the taste of PROP (6-n-propyl thiouracil) in aqueous solution was determined in 173 French Caucasian women deprived of retronasal olfaction by blowing an air stream into the nostrils. As expected, the detection thresholds were bimodally distributed, although as many as 73% of the subjects had thresholds above the antimode concentration and therefore qualified as non-tasters. Detection threshold, difference threshold, intensity perceptions and preference ratings were then determined for NaCl, sucrose, caffeine, Na saccharin and naringin in 20 tasters and 20 non-tasters. No differences were found between tasters and non-tasters for detection or difference thresholds of the various tastants. Intensity and preference ratings for solutions of NaCl, saccharin or caffeine were not influenced by taster status. Although ratings of sweetness intensity for sucrose solutions did not differ between tasters and non-tasters, concentrated sucrose solutions were more disliked by non-tasters than by tasters. Non-tasters rated naringin solutions as more bitter than tasters, but naringin preference ratings were independent of taster status. Some of these findings were unexpected and further studies are required to find out whether they stem from the odour-preventing procedure or are of biological or cultural origin.

Exercise-training reduces BAT thermogenesis in rats

In the energy balance equation, physical activity represents one component of energy expenditure. From various studies it appears that exercise-training does not affect clearly thermogenesis which depends on brown adipose tissue (BAT) activity. In the present work we examine how exercise-training can influence food intake and body weight regulation in relation to BAT thermogenesis. The proton conductance of the uncoupling protein of BAT was examined in male adult Wistar trained 2 h/day for 20 days and compared to that of sedentary (2 h of fasting instead of exercise) or control animals. All animals were provided with separate sources of the 3 macronutrients (protein, fat and carbohydrate) containing an identical percentage of vitamins, salt mixture and cellulose powder. At the end of training, rats were placed at 5 degrees C during 10 days, then during 4 days at 28 degrees C. This condition has been demonstrated to favour and amplify BAT responsiveness to moderate modifications of stimulation. The body weight of trained rats became significantly lower than that of the control and sedentary rats and this difference persisted all throughout the experiment. When placed at 5 degrees C, all rats increased their total ingestion: control rats enhanced fat intake, while sedentary and trained rats enhanced carbohydrate ingestion. When placed at 28 degrees C, all rats had identical total energy and that of the 3 items intakes. BAT proton conductance was about 40% lower in the trained compared with the sedentary plus the control rats. This indicated a lower BAT thermogenic activity in the trained animals. It could be concluded that exercise-training in rats induces negative energy balance; the reduced BAT activity could restrain weight loss and overeating.

Energy balance in an inbred strain of rats: comparison with the Wistar strain.

Food intake and body weight gain were examined in two groups of male rats (7 weeks): an inbred strain, Dark Agouti (DA, n = 12) and a noninbred strain, Wistar (n = 13). The animals were allowed to select their diet from separate sources of the three macronutrients protein, fat, and carbohydrate. After 10 days of adaptation to the diets, body weights and food intakes were measured for 3 weeks. During this period, meal patterns were recorded for at least 5 days in each rat. Then, rats were switched to a chow diet (UAR, A.O4) for 10 days. The total caloric intake of DA rats was 60% that of Wistar rats, while their body weight gain was 25% that of Wistar rats (1.3 g/day in DA vs. 5.3 g in Wistar). However, when energy intake was related to total body weight, there was no difference in energy ingestion. It was observed that DA rats ingested mainly proteins (45%) and fats (41%), while Wistar rats ingested an identical proportion of proteins and carbohydrates (40%). The percent of total white adipose tissue to total body weight was identical in both strains (6% on average). Brown adipose tissue thermogenic activity of DA rats was threefold higher than in Wistar rats. This could be one of the elements responsible for the lower body weight gain of this group of rats. Self-selected food intake of the inbred DA strain of rats, in contrast to what was expected, was greatly variable.

A method for long-term and accurate measurement and recording of the blood glucose level in man

We describe a technique of continuous and long-term withdrawal of venous blood which permits a continuous measurement and recording of the blood glucose level. The preparation and setting up of a special double lumen catheter are detailed. This technique provides very accurate blood glucose time course determination and requires the withdrawal of small amounts of blood.

Meal size: role of reflexly induced insulin release.

The amount of a particular food consumed during a meal is dependent on its sensory properties; moreover more food is consumed during a several course meal than during a single course one. The underlying physiological mechanisms are still unclear, but based on recent data, several hypotheses could be suggested. The determining effect of the sensory qualities of food on amount eaten could be dependent only on a direct action of incoming sensory information on the brain control systems. Reflex insulin secretions are triggered by sensory contact with food or food cues; the so-induced insulin secretions might play a crucial role in meal size determination. Finally, brain opiates possibly involved in the brain reward system might stimulate oral intake to a larger or lesser degree according to the hedonic hedonic properties of the presented food. Experimental arguments supporting these suggestions are presented.