Eating Rate Research Articles

Role of 5-HT receptors in the effect of d-fenfluramine on feeding patterns in the rat

The effect of d-fenfluramine, 1.5 mg/kg i.p., on meal patterns was studied in rats treated i.p. with 1 mg/kg metergoline or 0.5 mg/kg ritanserin or s.c. with 3 mg/kg (±)cyanopindolol. d-Fenfluramine significantly reduced eating rate, meal size and total intake in the first 4 h of testing and the effects were antagonized by metergoline. (±)Cyanopindolol reduced total intake and the effect of d-fenfluramine on this measure; the effect of d-fenfluramine on meal size (but not on eating rate) was also reduced by (±)cyanopindolol. Ritanserin only reduced the rate of eating and the effect of d-fenfluramine on this measure. The results suggest that 5-HT 1 receptors, possibly of the 5-HT 1B type, are involved in the ability of d-fenfluramine to cause satiety in freely feeding rats.

The single-item meal as a measure of binge-eating behavior in patients with bulimia nervosa

To determine whether the characteristics of binge eating could be observed in a single-item meal, in a laboratory, patients with bulima nervosa and controls ate two single-item meals and two multiple-item meals. When they were instructed to binge eat, the patients ate significantly more and for a longer time on both single- and multiple-item meals than did controls. When they were instructed not to binge, intakes of the two groups did not differ. Controls, but not most of the patients, showed deceleration in their eating rate when they were asked to binge. Intakes of the single- and multiple-item meals were significantly correlated for the patients under both sets of instructions. These results are consistent with previous reports in indicating that patients with bulimia nervosa eat differently from controls and suggest that a single-item meal can be used to examine the characteristics of binge eating in patients with bulimia nervosa.

Decreased reactivity to sweetness following chronic exposure to mild unpredictable stress or acute administration of pimozide

Consumption of a palatable wet mash was examined in rats subjected chronically (4-10 weeks) to unpredictable mild stress. Intake of mash containing 0, 10%, or 20% additional sucrose was normal in stressed animals. In control animals, the addition of 30% or 40% sucrose caused a decrease in the quantity of mash consumed, but increased the rate of eating. Both the increase in eating rate and the decrease in intake, at high sucrose concentration, were markedly attenuated in stressed animals (which therefore had higher intakes of very sweet mash and lower rates of eating, relative to control animals). Like chronic mild stress, the dopamine receptor antagonist pimozide (0.2 mg/kg) also increased the intake of a wet mash with 30% added sucrose, while decreasing the rate of consumption. Stressed animals were relatively insensitive to pimozide, though there were significant additive effects on duration of eating (increased) and on postprandial resting (suppressed). The failure of stressed animals to adapt their intake to increases in sweetness, and the similarities between the effects of chronic mild stress and acute pimozide, are compatible with the hypothesis that animals exposed to chronic mild stress are anhedonic.

Seasonal rhythms of human nutrient intake and meal pattern

Seasonal variations in the nutrient intakes and the meal patterns of humans were investigated by paying 315 adult humans to maintain a 7-day diary of everything they ate, when they ate it, and their subjective state of hunger. A marked seasonal rhythm of nutrient intake was observed with increased total caloric intake, especially of carbohydrate, in the fall, associated with an increase in meal size and a greater rate of eating. The subjects rated themselves hungrier at the end of the meal in the fall even though the larger meals resulted in a greater estimated amount of food in the stomach. In the winter and spring there was a strong negative relationship between the amount eaten in the meal and self-rated hunger at the end of the meal. This correlation was absent during the fall. The results suggest that even with modern heating and lighting seasonal rhythmicity of food intake persists in humans and is a major influence on eating that may act by suppressing satiety mechanisms.

Differential effects of d-fenfluramine, l-fenfluramine and d-amphetamine on the microstructure of human eating behaviour

An observational technique, demonstrated to provide reliable data under a variety of conditions, was used to evaluate the effects of d-fenfluramine, l-fenfluramine, d-amphetamine, and fenfluramine-amphetamine combinations on eating behaviour in human subjects. Following an overnight fast, subjects ate lunch from a dispenser allowing free access to a choice of ten sweet and savoury foods, of varying macronutrient composition. D-fenfluramine (30mg) and d-amphetamine (15mg) reduced food intake; l-fenfluramine (30mg) was essentially inactive. The net effects of d-fenfluramine and d-amphetamine on food intake were additive, but the behavioural mechanisms of action were different for the two drugs. D-amphetamine decreased the duration of the meal, as well as the time spent chewing or manipulating food and the number of bites, but had no effect on eating rate; by contrast, d-fenfluramine decreased the rate of eating, but had no effect on meal duration.

Restrained eating, obesity, and cumulative food intake curves during four-course meals

A four-course meal was presented to six obese and 18 normal weight women in which the second course was eaten ad libitum and the other three courses were fixed in amount. Eating behaviour was observed directly and intake was monitored via an electronic scale built into the table under the plate. Intake deceleration was observed in the normal weight women who scored low on the Herman-Polivy (1980) restraint questionnaire and on the cognitive restraint factor (F1) of Stunkard and Messick's (1985) questionnaire, whereas the normal weight and obese restrained women displayed linear cumulative food intake. In all groups, if deceleration occurred in the second course it was usually identical in the third and fourth courses, and constant eating rate persisted from the second course to the later courses. Food-specific eating rates were positively correlated to relative palatability, and removed deviation from linearity in cumulative intake over the four courses.

Objective measurement of eating rate during behavioral treatment of obesity

This study assessed changes in eating behavior of 10 obese women who participated in a behavioral weight control program. Eating rate, hunger, and satiety were measured during consumption of a standardized laboratory meal at weeks 1, 28 and 41 of treatment. Subjects increased their meal length (i.e., slowed their rate of eating) significantly from weeks 1 to 28. Increased meal length was associated with greater weight loss. Meal length returned to baseline levels at week 41, however, and there was no longer a significant relationship between changes in meal length and weight loss. Subjects indicated at all three assessment periods that they were significantly more satiated 15 minutes after their meal than at its immediate conclusion. These results are consistent with recommendations provided in behavioral weight control programs to slow the rate of eating. Clinical efforts must be directed toward sustaining changes in eating behavior, which appear to fade with time.

Rumen fill, forage palatability and alimentary behaviour in sheep

SUMMARYFive sheep were fitted with rumen cannulas and fed once daily ad libitumat 09.00 h with a low-quality mixed-grass hay or a good-quality lucerne hay. The effects of a second amount of the same hay or of the second hay distributed at the end of the large meal following the morning distribution, when rumen fill reaches its daily maximum, were investigated for feed intake, alimentary behaviour and rumen fill. The second distribution induced a true meal (200–400 g dry matter intake), except in the case of mixed grass offered after lucerne. On the basis of initial eating rate and the amount ingested, the highest palatability was for lucerne offered after mixed grass, and the lowest for mixed grass offered after lucerne. Diet selection was more pronounced with lucerne than with mixed grass, as indicated by the larger decrease in the neutral detergent fibre content of the fraction ingested. The true meals following the second distribution were associated with an increase in rumen fill up to 10% of the daily maximum observed without the second distribution. However, rumen fill with lucerne remained 1 kg lower than with mixed-grass hay, even after a second meal. It is concluded that the sensory response induced by a distribution of a sufficiently palatable hay is able to override the satiety signals due to rumen fill, and that there is a permanent balance between the stimuli related to the characteristics of the food available and those related to reticulo-ruminal digesta.

The shape of the cumulative food intake curve in humans, during basic and manipulated meals

The shape of the cumulative food intake curve of normal weight and obese women was studied during solid food lunches, artificially prolonged meals, and energetically enriched meals eaten in a laboratory setting. Subjects (86 normal weight, 50 obese) displayed consistent eating behaviour over 3–6 repeated meals, with marked differences between individuals. Aspects of eating behaviour were reflected in decelerated and nondecelerated (or linear) cumulative intake curves depending on changes or no changes in eating rate during the course of a meal, respectively. A change in eating rate was generally related to a decrease in bite size, with bite rate remaining constant, from the third temporal quarter of the meal onwards, resulting in a decelerated cumulative intake curve. The nondecelerated (linear) cumulative intake curve does not show this change in eating rate: in the first three temporal quarters bite size and bite rate were constant, whereas in the fourth temporal quarter bite size decreased slightly, compensated by a small increase in bite rate. Intraindividual ranges for meal parameters such as chewing time per bite, bite interval and initial eating rate indicated consistency of individual eating behaviour. In manipulation experiments with a subset of 21 subjects in which meals were artificially prolonged by an interval of 8 min, the cumulative intake curves did not differ significantly from the original cumulative intake curves in 10 nondecelerated (linear) eaters, but showed a change towards nondecelerated curves in 8 out of 11 decelerated eaters. In manipulation experiments with a subset of 34 subjects, who consumed similar meals, but energetically enriched by addition of either fat, protein, or carbohydrates, 25 of these subjects showed no change in the shape of their cumulative intake curves.

Effect of prefeeding lipid on food intake and satiety in man.

Experiments were carried out in normal volunteers to investigate whether preingestion of lipid reduces food intake. In the first set of experiments, 300 ml beef consomme soup with or without 60 g margarine was fed to each of six volunteers, followed 20 minutes later by either a low fat solid meal or a preselected appetising meal. Subjects were allowed to eat as much of the meal as they wished. Preingestion of the high fat soup had no significant effect on the consumption of either of the solid meals and did not influence sensations of hunger or fullness. As we have previously shown that prefeeding a fatty soup delays gastric emptying of a subsequent meal, this suggests that gastric distension may play a relatively minor role in regulating food intake. In the second set of experiments, we studied the effect of ingesting either a high fat breakfast (65 g fat, 927 kcal) or a similar low fat breakfast (8-1 g fat, 418 kcal) on the consumption of a preselected appetising lunch in six healthy volunteers. The high fat breakfast significantly reduced the amount of the meal eaten at lunchtime (p less than 0.02), the total energy intake from the meal (p less than 0.05) and the rate of eating (p less than 0.05) compared with the low fat breakfast. When the subjects were presented with their lunchtime meal they felt significantly less hungry after the high fat breakfast (p less than 0.05). Only a small proportion of either meal (15% of the high fat meal v 12% of the low fat meal) remained in the stomach and plasma glucose concentrations had returned to fasting levels. Plasma triglyceride concentrations were much higher at lunchtime after ingestion of the high fat breakfast (p<0.001). The energy intake from the breakfast and lunch combined was not significantly different on the high fat breakfast day, indicating that the energy consumption at lunch compensates for the amount eaten at breakfast. These results are compatible with the concept that the interaction of nutrients with small intestinal receptors may play a part in limiting food intake.

The anorectic effect of SK&amp;F 38393, a selective dopamine D1 receptor agonist: a microstructural analysis of feeding and related behaviour

An observational study was undertaken to provide a microstructural analysis of the effects of the selective dopamine D1 receptor agonist, SK&F 38393, on feeding and associated behaviours in the rat. Adult, male non-deprived rats were adapted to eating a meal of sweetened mash in a 30-min period. SK&F 38393 (3.0 and 10 mg/kg, SC) significantly reduced food consumption). It also reduced the frequency of feeding bouts and the local rate of eating, while there was an increase, at 10 mg/kg, in the mean duration of individual feeding episodes. The D1 receptor agonist also reduced the total duration of locomotor activity, but did not affect the total duration of rearing, grooming, sniffing, oral behaviours (other than feeding), or resting. The frequency of bouts of locomotion, rearing, grooming, and sniffing were reduced by SK&F 38393. Consideration of the time-courses for the several responses suggested that SK&F 38393 did not materially affect the form and sequence of behavioural responses in the test, although some changes occurred.

Feed intakes and meal patterns of sheep during pregnancy and lactation, and after weaning

Four cross-bred ewes were kept in individual pens from the last month of pregnancy until the third week of weaning after a 5-week lactation; lambing occurred in late March. The ewes were offered a complete pelleted feed ad libitum, and every few days the feeding behaviour of each was monitored by continuous recording of the weight of the feed container. The weight and timing of each meal was used to calculate mean meal size and length, intermeal interval, hunger and satiety ratios. The increase in daily intake which occurred after parturition was due to increases in meal size, rate of eating and meal frequency. Intake was lower in the period of the day from 0400 hrs to 0800 hrs than during any of the 4-h periods between 0800 hrs and 2400 hrs, with intermediate values at 2400-0400 hrs. The time of day had no effect on meal size or rate of eating. These results are compared with the predictions of a model designed to predict meal occurrences in sheep and the differences used to suggest improvements to the model.

Patterns of food selection during meals in women with bulimia

Eating behavior of women with bulimia was compared with that of control subjects who had no eating disorders. Both groups were presented with two buffet-style multiple-item meals. In one meal subjects were instructed to eat normally and in the other they were instructed to eat as much as they could. The eating patterns of patients differed from control subjects in the quantity of food selected and in the rate of eating. During the binge meal, patients spent more of their meal time eating dessert and snacks than did control subjects and began their dessert and snack consumption earlier than control subjects. Patients distributed their meat consumption more evenly across the meal, whereas control subjects ate meat predominantly early in the meals. Most patients consumed either more or less than control subjects when not binge eating, indicating that the eating disturbances in bulimic patients are not confined to episodes of binge eating.

Microstructural analysis of the anorectic effect of N-0437, a highly selective dopamine D 2 agonist

Drug actions, mediated by dopamine D 2 receptors, have been shown to reduced food consumption in rodents. The present study used a microstructural approach to feeding responses to determine the behavioural changes which underlie the anorectic effect of a selective D 2 agonist, N-0437. Non-deprived male rats were trained to consume a palatable, sweetened mash in a 30 min test under familiar test conditions. N-0437 (1.0 and 3.0 mg/kg) significantly reduced food intake, but had no effect on the duration of feeding, the duration and frequency of feeding bouts, or on the time course of feeding. Its anorectic effect depended upon a selective reduction in the rate of eating. Microstructural analysis of other behavioural changes which followed treatments with N-0437 indicated that, at 0.3 mg/kg, the drug may have selective dopamine autoreceptor activity, but at 1.0 and 3.0 mg/kg it acts postsynaptically at D 2 receptors. The results show that the anorectic effects of N-0437 can be clearly distinguished from the effects of psychomotor stimulants like d-amphetamine or cocaine, but they overlap in part with the effect of the mixed D 1/D 2 agonist, apomorphine. The results are discussed in relation to a proposed D 2 receptor-mediation of one component of the behavioural changes that underlie feeding satiation.

The influence of pasture and animal factors on the consumption of pasture by grazing sheep

Interrelations of animal and pasture factors to account for variance in (i) the time spent grazing (GT, H/day) and (ii) the rate of eating (IR, OM/h) in data collected over 2.5 years on Corriedale sheep (adult castrated males) grazing pasture of mixed perennial/annual species in south-western Victoria were examined by sequentially adding factors and analysing in nonlinear regression relationships. Three plant and two animal factors accounted for almost 80% of the variance (100R2) in the GT of sheep grazing on green pasture in the period from March to November (n = 176). Five factors, including a stress factor related to environmental conditions, accounted for 82.5% of the variance in IR of sheep grazing through the green pasture period from March to December (n = 192). Pasture factors associated with organic matter digestibility were also examined. Total pasture mass (H, t DM/ha) and the green proportion of the pasture (G, %DM) accounted for 74.6% of the variance in D (n = 232). The implications of these relationships for developing an understanding of the biological basis for intake control and compensatory growth of animals are discussed.

Corrigendum - The influence of pasture and animal factors on the consumption of pasture by grazing sheep

Interrelations of animal and pasture factors to account for variance in (i) the time spent grazing (GT, H/day) and (ii) the rate of eating (IR, OM/h) in data collected over 2.5 years on Corriedale sheep (adult castrated males) grazing pasture of mixed perennial/annual species in south-western Victoria were examined by sequentially adding factors and analysing in nonlinear regression relationships. Three plant and two animal factors accounted for almost 80% of the variance (100R2) in the GT of sheep grazing on green pasture in the period from March to November (n = 176). Five factors, including a stress factor related to environmental conditions, accounted for 82.5% of the variance in IR of sheep grazing through the green pasture period from March to December (n = 192). Pasture factors associated with organic matter digestibility were also examined. Total pasture mass (H, t DM/ha) and the green proportion of the pasture (G, %DM) accounted for 74.6% of the variance in D (n = 232). The implications of these relationships for developing an understanding of the biological basis for intake control and compensatory growth of animals are discussed.

Quantitative analysis of nycterohemeral eating and ruminating patterns in heifers with different voluntary intakes and effects of monensin.

The nycterohemeral pattern of eating and ruminating behavior was examined in six heifers given ad libitum access to a corn silage-based diet with or without 100 mg monensin.hd-1.d-1 in a two-period crossover design. Rhythm components (no. of cycles/24 h) were characterized by the finite Fourier transform of 24-h mastication activities series measured over 7 d. Analysis of variance of the daily mean of hourly activities and rhythm components 1 to 12 showed significant effects of heifer (H), monensin treatment (T), period (P) and T x P x H interactions. A reparameterization of the finite Fourier transform yielded the amplitude and the phase for each rhythm component and allowed the plot of periodograms and phase diagrams, respectively. Rhythm components 1, 2 and 3 contributed primarily in explaining the total dispersion of 24-h eating and ruminating mastication series. The major effect of monensin was to increase the phase at rhythm component 1, delaying by 1 h in the onset of rumination after the morning feeding. Heifer effects were significant and appeared related to variations in daily voluntary intake (VI) of individual heifers. Heifer 5, with the largest VI, had two main eating periods and the highest rate of eating. Heifer 4, with the smallest VI, partitioned mastication activity throughout the day into four main eating and ruminating periods. Differences among animals in their nycterohemeral chewing behavior patterns may be related to differences in forestomach structure associated with a larger VI capacity by animals having mastication rhythm components 1 and 3.

Continuous intraventricular infusion of neuropeptide Y evokes episodic food intake in satiated female rats: Effects of adrenalectomy and cholecystokinin

In these studies the pattern of feeding behavior during continuous intraventricular (IVT) infusion of NPY for 4 hr in the satiated female rat was monitored. Whereas saline infusion was ineffective, each of the three doses of NPY (117, 470 or 1175 pmol/hr) increased feeding during the entire 4 hr infusion and 2 hr postinfusion period. The cumulative food intake at the end of 4 hr of NPY infusion was enhanced in a dose-related fashion between 0, 117 and 470 pmol/hr; at 1175 pmol/hr food intake plateaued. In addition, the latency to initiate feeding response decreased in a dose-related fashion and feeding occurred in discrete (35–45) episodes during the 4 hr infusion period. Further, the total time feeding and local eating rate (g/min) increased significantly in response to the higher rates of NPY infusion. Concurrent infusion of cholecystokinin (CCK) at either equimolar or 2.5 × NPY dose, affected neither the NPY-induced cumulative food intake nor any other parameter of feeding behavior. On the other hand, cumulative food intake was significantly decreased in adrenalectomized rats in response to NPY infusion (470 pmol/hr); a response due primarily to a marked suppression in some, and almost complete cessation of food consumption in other rats during the second 2 hr period of NPY infusion. These studies show that continuous central infusion of NPY can produce sustained, intermittent feeding behavior and adrenalectomy significantly curtailed the duration of NPY effectiveness. These observations are in line with the view that an increase in NPY secretion in relevant brain site(s) may be responsible for the intermittent high rate of food consumption during the dark phase of the daily light-dark cycle in the rat.

Is there a metabolic component to counterregulation?

A highly structured test meal situation was used to examine the metabolic and behavioral response of restrained and unrestrained eaters to a disguised calorific preload. Both restrained and unrestrained eaters ate initially more quickly after drinking a disguised glucose preload, compared with those who drank a glucose-free preload. Restrained eaters showed a comparatively greater increase in rate of eating, which tended to persist as a greater overall food consumption. The unrestrained group compensated for their initially greater consumption by eating less later in the meal. The excess eating occurred in conjunction with the release of excess insulin compared with circulatory glucose in response to the preload. In the unrestrained subjects, this declines together with the compensatory decrease in food consumption. For restrained eaters, the elevation of insulin/glucose ratio persisted and was comparatively greater, in conjunction with a persistent and relatively greater enhancement of food intake. Subjective reports and ratings indicated that the subjects were aware of neither the presence nor the behavioral and metabolic effects of the preload. The results suggest a possible metabolic component to the phenomenon of counterregulation.

Comparisons of the effects on satiety and eating behaviour of infusion of lipid into the different regions of the small intestine.

Food intake and feelings of hunger and fullness were monitored in paired studies carried out in two groups of six healthy non-obese male volunteers during infusion of isotonic solutions of either a 50% corn oil emulsion or saline into the jejunum or into the ileum. Infusion of the lipid emulsion at a rate of 1.2 ml/min (4.9 kcal/min) into either the ileum or the jejunum significantly reduced the period of eating (p less than 0.01) and the quantity of food consumed (p less than 0.01), but neither affected the rates of drinking or the amount of fluid consumed. Infusion of the lipid emulsion into the jejunum also significantly reduced the sensations of hunger before the meal (p less than 0.05), and the rate of ingestion (p less than 0.01). Ileal infusion did not influence these indices. The results suggest that jejunal and ileal infusion of lipid reduces the size of the meal that could be consumed possibly by inhibiting gastric emptying. The alleviation of hunger before ingestion and the slower rate of eating, however, suggests that jejunal lipid activates an additional mechanism that influences the appetite centre in the hypothalamus directly.