Eating Rate Research Articles

Effects of Naltrexone on Food Intake and Changes in Subjective Appetite During Eating: Evidence for Opioid Involvement in the Appetizer Effect

Yeomans, M. R. and R. W. Gray. Effects of naltrexone on food intake and changes in subjective appetite during eating: evidence for opioid involvement in the appetizer effect. Physiol Behav 62(1) 15–21, 1997.—The effects of 50 mg naltrexone on eating and subjective appetite were assessed in a double-blind placebo-controlled study with 20 male volunteers. Appetite was monitored using a disguised digital balance connected to a micro-computer, which constantly monitored the amount of food remaining, and which automatically interrupted feeding for 30 s after every 50 g consumed to allow appetite ratings to be made. Half the subjects ate pasta with a cheese sauce, and the remainder pasta with a tomato sauce. Subjects ate significantly less of both foods after 50 mg naltrexone than in either the placebo condition or on the initial (familiarisation) day. Naltrexone also reduced the rated pleasantness of both foods, and reduced overall eating rate. When best-fit quadratic functions were used to describe changes in rated hunger in relation to intake within the meal, naltrexone abolished the positive linear component reflecting the initial stimulation of appetite without altering either intercept or the negative quadratic function. Although mood ratings suggested that naltrexone had a mild sedative effect, mood changes alone could not explain the effects of naltrexone on appetite. Overall, these data suggest a specific role for opioids in the stimulation of appetite through palatability.

Neuropeptide Y stimulates feeding but inhibits sexual behavior in rats. 1985.

The effects of neuropeptide Y (NPY), a tyrosine‐rich peptide found in the rat brain, on feeding and sexual behavior were studied in male and female rats. Intraventricular (ivt) injections of NPY during the final hours of the light period induced feeding in a dose‐related manner. While the lowest dose tested (0.02 nM) was without effect, higher doses (0.12, 0.47, 2.3 nM) uniformly elicited feeding with a latency of about 15 min in male rats. With the most effective dose, 0.47 nM, the increased food intake was due to an increased local eating rate. In contrast, the pattern of feeding behavior after a related peptide, rat pancreatic polypeptide (rPP), was quite different and less impressive. During the first hour, only one ivt dose of rPP (0.45 nM) evoked an increase in food intake, due to an increased time spent eating. Further, the effects of NPY on food intake were greater during the nocturnal period. Interestingly, increased food intake in nocturnal tests (4 h) was due solely to augmented intake during the first 60 min after ivt administration.In mating tests, initiated 2 h after the onset of darkness and 10 min after ivt administration of peptide, all but the lowest dose of NPY (0.01 nM) drastically suppressed ejaculatory behavior. Most rats treated with higher doses of NPY (0.02, 0.12, or 0.47 nM) mounted and intromitted only a few times before the cessation of sexual activity, and elongated latencies to the initial mount and intromission were observed. In contrast to the dramatic NPY‐induced suppression of ejaculatory behavior, rPP (0.11 and 0.45 nM) was without effect on copulatory behavior. To substantiate further that the impairment of sexual behavior seen in NPY‐treated rats was not due to an attenuated sexual ability, an additional experiment was performed. Penile reflexes, including erection, were monitored 10 min after ivt injection of NPY (0.12 nM), rPP (0.11 nM), or saline. No effect of NPY or rPP was observed on the proportion of rats showing erection or latency to initial erection, or in the number of erections per test. In fact, a slight facilitation of penile dorsiflexion responses was seen after NPY. These findings suggest that NPY selectively depresses sexual motivation in the male rat.In ovariectomized female rats responding to estrogen plus progesterone with a good level of sexual receptivity (lordosis quotient > 70), ivt saline and 0.01 nM NPY were without effect on sexual behavior. However, higher doses of NPY (0.12 and 0.47 nM) promptly suppressed sexual behavior in tests initiated 10 min after treatment. A significant 50% decrement in receptivity and a virtual elimination of proceptive behavior were observed. Further, although a low level of mounting (one to five mounts in 15 min) was seen in both the saline (33% mounting) and the 0.01 nM NPY (38% mounting) treated groups, none was observed in animals treated with the higher NPY doses. These observations indicate that NPY may also suppress female sexual behavior.

One-year follow-up of cognitive-behavioral therapy for obese individuals with binge eating disorder.

The results of a 1-year posttreatment follow-up of 93 obese women diagnosed as having binge eating disorder (BED) and treated with group cognitive-behavioral therapy (CBT) followed by weight loss treatment are described. The group as a whole maintained both reductions in binge eating and abstinence rates fairly well. However, they regained the weight lost during treatment. Those who stopped binge eating during CBT maintained a weight loss of 4.0 kg over the follow-up period. In contrast, those who continued to binge gained 3.6 kg. Twenty-six percent of those abstinent after CBT met criteria for BED at follow-up and had gained weight, whereas the remaining 74% had lost weight. Stopping binge eating appears critical to sustained weight loss in BED.

Differential circadian eating patterns in two psychogenetically selected strains of rats fed low-, medium-, and high-fat diets.

Spontaneous eating patterns in male, inbred Roman high- and low-avoidance rats (RHA/Verh, RLA/Verh) were continuously recorded while animals were successively offered three isocaloric (approximately 16.5-kJ/g) diets: a low-fat, high-carbohydrate diet (LF; 3.3% fat), a medium-fat diet (MF; 18% fat), and a high-fat diet (HF; 40% fat), the latter being followed once again by the LF diet. Under the conditions of this experiment, overall 24-h food intake did not differ significantly between RHA/Verh and RLA/Verh rats, but was significantly higher for both rat strains on the MF and HF diets than on the LF diet. Despite the similar 24 h-food intake, RHA/Verh rats ate transiently less than RLA/Verh rats during the third quarter of the dark phase under all dietary conditions. These differences were due to the RHA/Verh rats' longer intermeal intervals (with all diets) and smaller meals (with the MF and HF diets) and were compensated for during the last 3 h of the dark phase. On the LF diet, dark-phase meal frequency was higher and both nocturnal meal size and mean eating rate within meals were lower in RLA/Verh rats than in RHA/Verh rats. With the MF and HF diets, mean nocturnal meal size and meal duration were higher and mean eating rate was lower in RLA/Verh rats than in RHA/Verh rats. For both strains, nocturnal meal size was significantly higher with the MF and HF diets than with the LF diet, and nocturnal meal frequency was lower with the HF diet than with the other two diets. Although body weights were similar at the start of the study, RLA/Verh rats gained significantly more weight than did RHA/Verh rats by the end. As has often been the case with other aspects of behavior studied, differences in neuromodulatory systems (e.g., serotoninergic and dopaminergic) between RHA/Verh and RLA/Verh rats may directly or indirectly contribute to the subtle differences in eating patterns observed here.

Metergoline antagonizes fluoxetine-induced suppression of food intake but not changes in the behavioural satiety sequence

In this study continuous monitoring was used to yield a true behavioural record. This allows a bidimensional account of drug effects on every unit of behaviour. Behavioural dimensions of duration (dur) and frequency (frq) measures were utilized to monitor the effects of an ED 50 anorectic dose of fluoxetine (10 mg/kg IP) on the behavioural satiety sequence and the effect of a metergoline (1 mg/kg IP) challenge. Fluoxetine reduced food intake by 45% ( p < 0.005). The local eating rate was also reduced ( p < 0.001), demonstrating a marked slowing of eating behaviour. Eating behaviour was reduced (frq p < 0.005) as was grooming (frq p < 0.05) and activity. Resting was increased (dur p < 0.05) and temporally advanced. There was no gross disruption of behaviour and the profile was adjusted in a way consistent with the expression of satiety. Fluoxetine-induced changes were very similar to those produced by prefeeding. Metergoline antagonised fluoxetine's effect on intake and eating duration (dur p < 0.05). However, metergoline did not antagonise the effect of fluoxetine on the frequency of eating (frq p < 0.005), thus increasing the amount consumed per eating episode. Grooming (frq p < 0.005) and activity also remained reduced. At this dose fluoxetine-induced suppression of eating is serotonin dependent as it is reversed by metergoline. Fluoxetine-induced suppression of eating at this dose is consistent with the normal operation of satiety. Fluoxetine-induced slowing of behaviour appears to be mediated by a separate mechanism.

Eating disorders and weight concern among lesbians.

This study estimated rates of bulimia nervosa and binge eating, and assessed risk factors among 203 lesbians. Participants completed questionnaires containing measures addressing lifestyle, self-esteem, body esteem, attitudes about attractiveness, and disordered eating. The rate of bulimia nervosa among lesbians was similar to that of heterosexual women, but binge eating disorder was more frequent. Eating as negative affect regulation was a more significant predictor of binge eating than body dissatisfaction or dieting. Lesbians were not significantly different from heterosexual women in attitudes concerning weight and appearance, or dieting. Self-esteem was significantly related to body esteem, and actual-ideal weight discrepancy was associated with body dissatisfaction, suggesting that lesbians are not immune from the effects of not meeting societal ideals of thinness. Increased lesbian/gay involvement was associated with lower weight concern. Implications for models of risk for eating disorders, and understanding the experience of lesbians, are discussed.

Feeding Patterns and Swine Performance in Hot Environments

Two experiments were conducted to determine modifications in eating behavior of heat-stressed pigs using gilts and barrows. Heat-stressed pigs were maintained at environmental temperatures that caused voluntary 13% and 26% reductions in daily feed consumption compared to control temperature pigs of the same weight. For control temperature pigs, there was a 50% reduction in number of meals and a threefold increase in meal size as animals grew from 40 to 100 kg. The number of daily meals and rate of eating (g/min) for heat-stressed pigs were remarkably similar to control pigs of the same age. However, for heat-stress treatments, the duration of meals was substantially reduced which apparently was the primary method of behaviorally adjusting to heat stress. Heat stress reduced liver, heart, stomach, and large intestine weights, and tended to reduce backfat thickness indicating that pigs under heat stress had reduced maintenance requirements. Heat stress did not affect feed conversion, but substantially reduced rate of gain.

Effects of single-space feeder design on feeding behaviour and performance of growing pigs

AbstractComputerized food intake recording systems of various designs are used by research, centres and breeding companies to monitor the individual food intake of pigs kept in groups. In the present experiment, three feeder designs are compared in order to estimate the effect on performance and feeding behaviour. Ninety entire male pigs (34 (s.e. 0·6) kg) were allocated in three replicates to pens of 10 pigs; each pen containing one of three different feeder entrance designs: low (head-guard), medium (full-length standard race), and high (enclosed pneumatic race) protection against disturbance of the feeding pig. No significant differences were found between treatments in daily food intake, daily live-weight gain, food conversion ratio, number of visits per day and daily feeder occupation. Pigs with access to an enclosed race had longer visits than pigs on the two other treatments, and they also ate more per visit (4·8, 4·8 and 6·2 (s.e.d. = 0·37) min per visit; 172, 157, and 202 (s.e.d. = 11·1) g per visit; means of low, medium and high protection, respectively). The enclosed race was not only the most protective, it was also the most difficult to enter, and this decreased accessibility of the food may have given rise to the changed feeding pattern displayed by pigs using this type of race. Access to a feeder with low protection resulted in a faster rate of eating (36·9, 33·2, and 32·8 (s.e.d. = 0·82) g/min; means of low, medium and high protection, respectively) indicative of a more forced feeding behaviour.

Dopamine Receptor Subtype Agonists and Feeding Behavior

Stimulation or blockade of various dopamine receptor subtypes is associated with reduced feeding. For example, D2 receptor agonists suppress feeding in food-deprived and free-feeding rats, and in rats given access to a highly palatable diet. Similarly, reduced food intake is associated with the actions of diverse D1 receptor agonists, and these compounds can interact synergistically with D2 receptor agonists to potentiate reductions in feeding. Using microstructural analysis to compare D1 and D2 agonist effects, specific differences emerge in their modes of action. D1 agonists reduce the duration of feeding, primarily by decreasing the frequency of feeding bouts, whereas D2 agonists reduce the local rate of eating. However, since D1 agonists uniquely reduce feeding in the absence of other behavioral impairments and are less disruptive of the pattern of feeding behavior, it has been suggested that D1 agonists are more likely than D2 agonists to act on central mechanisms regulating food intake. Moreover, only D1 agonists are effective in suppressing sucrose sham-feeding, suggesting that D1 receptor stimulation may promote satiety. Nevertheless, many questions remain. For example, antagonist studies have implicated 5-HT receptor stimulation in the anorectic effects of D1 agonists, suggesting that further pharmacological and behavioral analyses of receptor-subtype agonist effects are required. Above all, recent developments in the classification of dopamine receptor subtypes reveal the need for new studies examining the involvement of D3, D4 and D5 receptors in feeding.

Long-term correlates of child sexual abuse: Theory and review of the empirical literature

Since Browne and Finkelhor's (1986) seminal review of the impact of child sexual abuse, there has been a dramatic increase in the child sexual abuse literature. Because of this tremendous growth in the literature, a more current review is warranted. The focus of this paper is a review of the long-term correlates of child sexual abuse published since 1987. Sexually abused subjects report higher levels of general psychological distress and higher rates of both major psychological disorders and personality disorders than nonabused subjects. In addition, child sexual abuse survivors report higher rates of substance abuse, binge eating, somatization, and suicidal behaviors than nonabused subjects. Adult survivors of child sexual abuse report poorer social and interpersonal relationship functioning, greater sexual dissatisfaction, dysfunction and maladjustment including high-risk sexual behavior, and a greater tendency toward revictimization through adult sexual assault and physical partner violence. The long-term correlates of child sexual abuse are conceptualized within a theoretical framework based on a theory of emotional avoidance. Although more recent empirical findings have demonstrated improved designs and methodology, these studies continue to be limited in their generalizability. Recommendations for future research are discussed.

Voluntary intake: a limiting factor to production in high-yielding dairy cows?

AbstractIn principle, food intake by lactating dairy cows might be limited by rate of eating, capacity to produce saliva, rumen or intestinal capacity, rates of digestion and passage of food residues, or by factors such as chemicals and osmolality in the rumen. It is likely that a combination of these is used by the central nervous system to control intake. In practice, the positive relationship between digestibility and intake of forages means that high-quality material must be offered to cows during lactation if a reduced level of concentrate supplementation is envisaged but undue mobilization of body reserves avoided. Better supplementation is possible, both in terms of more frequent, smaller allocations, and of more appropriate concentrate composition with regard to the composition of the basal forage. Intake of maize silage dry matter is usually greater than for grass silage and a mixture of the two, perhaps offered in free or restricted choice, is likely to become more widely practised. Changes in body reserves are difficult to monitor and this has made it difficult to resolve the question of the magnitude of diet/environment interactions, i.e. is the same breeding and selection programme appropriate for those animals which are intended to be pushed to high yields in intensive systems and those intended to be given principally forages in semi-extensive systems?

The effects of work on food intake and ingestive behaviour of draught cattle and buffalo given barley straw

AbstractIn the first experiment the animals were worked for 5h/day and/or given 17 h access to food. In the second experiment they were worked for 4 h/day and/or given 20 h access to food. When animals were prevented from feeding on barley straw for 7 h/day their dry-matter intake (DMI) was significantly less than when they were given 24 h access to food. When feeding was prevented for only 4 h/day food intake was not significantly different from that with 24-h access.A study of feeding behaviour (experiment 2) suggested that when most animals were deprived of food for 4 h they maintained similar intakes to those on ad libitum feeding by increasing their rate of eating, rather than by increasing the time they spent eating. Preventing food intake for 4 h/day was associated with little change in time spent ruminating during the day. On all treatments, the buffalo spent significantly less time eating and more time ruminating than the cattle.Work, during the periods when food was withheld, had little effect on the DMI of either the buffalo or cattle compared with restricted feeding. No rumination occurred during the time that the animals were at work. However on working days, time spent ruminating was similar to that seen on restricted feeding days, but the animals spent more time ruminating later in the day than when they were able to ruminate during the middle of the day.

The selective dopamine uptake inhibitor GBR 12909: Its effects on the microstructure of feeding in rats

Previous experiments have investigated the anorectic effects of mazindol and cocaine, both of which can inhibit dopamine (DA) uptake into presynaptic terminals but do not do so selectively. GBR 12909, however, is an example of a potent and selective inhibitor of DA uptake and therefore, the present study was concerned with investigating its possible effects on feeding behavior in nondeprived rats given access to a sweetened palatable diet. GBR 12909 (5–20 mg/kg, IP) was injected 2 h before a 60 min observation test. It produced a significant reduction in food intake, as a consequence of a reduction in the duration of feeding, without reducing the rate of eating. This anorectic profile is consistent with earlier findings for mazindol and cocaine. The other main behavioral effect of GBR 12909, observed in the present study, was to induce intense sniffing activity, but, unlike cocaine, it did not suppress grooming or induce hyperlocomotion. This selective behavioral effect of GBR 12909 indicates that sniffing can be isolated as one component of a broader array of components typically associated with DA-related stereotyped behavior.

A-68930, a novel potent dopamine D1 receptor agonist

A-68930 [1R, 3S)-1-aminomethyl-5,6-dihydroxy-3-phenylisochroman HCI] is a novel, potent and selective dopamine D1 receptor agonist. Previous reports have shown that the selective D1 partial agonist, SK & F 38393, reduced food consumption in rats and mice. The aim of this study was to undertake a microstructural analysis of the effects of A-68930 on food intake and feeding behaviour in non-deprived male rats trained to consume a highly palatable diet in a 20min period. A-68930 (0.1-1.0mg/kg, s.c.) produced a dose-dependent reduction in food intake which was due to a reduction in the frequency of bouts of feeding but not to a reduction in bout duration. A-68930 had little effect on the latency to initiate feeding or on the local rate of eating. Hence, it had a selective action on the parameters of eating, which is distinctly different from the effects of selective D2 agonists or of indirectly acting psychomotor stimulants like cocaine. A-68930 also increased grooming by lengthening the grooming bouts, and reduced locomotion and rearing responses. At the largest dose, immobility was increased. The anorectic effect of A-68930 may reflect, at least in part, the increased grooming it produces.

Eating rates in normal and hypothalamic hyperphagic rats

Two experiments were conducted to determine if hypothalamic hyperphagic rats eat at a faster than normal rate and if slowing the rate of eating would reduce their overeating. Experiment 1 used a 45 mg pellet eatometer to measure 24-h meal patterns and eating rates in control rats and rats made hyperphagic with medial hypothalamic (MH) knife cuts. The MH hyperphagic rats consumed larger and more frequent meals but ate at a slower rate than did control animals during both the dynamic and static phases of the syndrome. In Experiment 2, rats were given 30-min test meals with the same pellets presented in food cups (rather than one pellet at a time as with the eatometer). The MH rats consumed the pellets at the same rate as the controls, although their meals were twice as large. Experiment 1 also determined if slowing the rate of eating would reduce MH hyperphagia; eating rates were constrained by increasing the delay between successive pellet deliveries (normally <1 s). An interpellet delay of 20 s reduced meal size and increased meal length and frequency but did not reliably reduce 24-h food intake in normal rats and dynamic or static phase MH rats. Interpellet delays of 40 or 60 s reduced daily food intake of static phase MH rats but only to control levels. These results indicate that MH hyperphagia is not associated with elevated feeding rates and is relatively unaffected by constraints on the rat's rate of eating.

Eating patterns of lactating dairy cows of three different breeds fed grass ad lib

Eating behavior of lactating cows of three breeds (Holstein-Friesian = HF, Simmental = SI, and Jersey = JER) was compared in the present study. The cows were kept in a loose housing system and fed grass and hay ad lib along with concentrates. Within 11 days, 1396, 1504, and 1682 grass meals were recorded and analyzed for HF , SI, and JER cows, respectively. In cows of all three breeds, 89% of the grass meals (=94% of the total grass intake) occurred during the light phase (0400–2200) and peaks of grass intake with large meals were always observed shortly after refilling the troughs. A similar diurnal distribution was evident for concentrate intake, but was less pronounced (28% eaten during the dark phase), and peaks of concentrate intake occurred also in the evening and after midnight. Hay intake was negligible and was not considered for meal pattern analysis. JER cows ate generally less than HF or SI cows, but spent more time eating. Grass meal frequency was higher, but grass meal size and mean eating rate within grass meals was smaller for JER cows than for HF and SI cows. Significant correlations between the size of grass meals and the duration of either the interval preceding or following that same meal were observed only for some animals (in particular JER and SI cows) during the main eating period in the morning (0800–1300), but barely in the afternoon (1300–1700). Thus, the short-term physiological control of meal-taking in dairy cows kept under normal farming conditions seems to be markedly influenced by external factors. Nevertheless, the data reveal differences in eating patterns of lactating HF, SI, and JER cows. Whether or not the observed differences in eating patterns have physiological consequences remains an interesting question for future investigations.

Lack of experimental evidence for pheromonal inhibition of reproduction among queens in the ant Leptothorax acervorum

Abstract. This paper describes an experimental test of the hypothesis that queens in multiple-queen (polygynous) societies of ants inhibit the reproduction of nestmate queens with pheromones. Three colonies of the facultatively polygynous ant Leptothorax acervorum with marked queens were each observed for 75 h, in three phases of 25 separate, hour-long bouts per phase, over 4-8 weeks in total. In each colony, all queens were present for the first phase; for the second phase, queens were removed so that only the queen initially laying least eggs (the focal queen) was present; and all queens were again present for the last phase. The pheromonal inhibition hypothesis predicts that in each colony the fecundity (egg production) of the focal queen should have risen in the second phase and fallen in the third phase. However, although the focal queen's fecundity did rise in phase 2 in each colony, these rises were small and were maintained in phase 3 in two out of three colonies, suggesting that the initial increase was not due to the experimental treatment. In addition, the focal queens' rates of egg eating, feeding from workers and larvae, grooming, receiving grooming and handling brood either did not change with the experimental treatment or changed in different directions across the three colonies. Therefore this experiment found no firm evidence among L. acervorum queens either for strong, short-term pheromonal inhibition of reproduction or for inhibitory effects of queens on other queens' behaviour.

混合飼料の給与時間が去勢牛の採食量,採食速度および採食継続確率に与える影響

混合飼料の給与時間が去勢牛の採食量,採食速度および採食継続確率に与える影響

Influence of method of conservation of lucerne on factors associated with voluntary intake in sheep

This experiment measured the voluntary intake and rate of eating of sheep fed lucerne (Medicago sativa) that had been conserved as sun-dried material or as silage at 3 different DM contents (29.2, 33.1, and 51.2%). Changes in rumen osmolality and palatability due to diet were measured. Palatability was assessed by introducing feed directly into the rumen and measuring the subsequent oral intake. Eight sheep with rumen fistulae were used in two 4 x 4 latin squares, which allowed for adjustment for carryover effects. There was no significant (P&lt;0.05) difference between voluntary intakes of lucerne conserved as sundried material and as silages of various DM contents (mean intake 1189 g DM/day). The lack of difference in intake was attributed to the high quality of fermentation of the silages. Rate of eating was also generally similar for all diets. Evidence from measurements of palatability and rumen osmolality support these observations. Palatability appeared not to influence the voluntary intake of any of the diets, because the sheep reduced their daily oral intake by an amount similar to that introduced into the rumen. Under normal feeding conditions, rumen osmolality was also similar for all feeds and was relatively consistent for the 9 h immediately after the start of feeding. While rumen osmolality per se may affect voluntary intake, the lack of response reported here for changes in osmolality due to diet support the lack of response reported for feed consumption.

Mechanisms of Foraging in Mammalian Herbivores: New Models of Functional Response

The outcome of many high-order processes in ecology depends on the way in which the abundance and distribution of plants affect the eating rate of mammalian herbivores. However, simple, mechanistic models describing the operation of the functional response of these animals have failed to emerge. We offer new models describing the effects of spatial and morphological characteristics of plants on the intake rate of plant tissue by mammalian herbivores feeding within plant patches. We structure our models to respond to three patterns of plant availability: (1) spatially dispersed, apparent plants; (2) spatially dispersed, nonapparent plants; and (3) spatially concentrated plants. We depart from the traditional representations of predator functional response in assuming that searching for food and processing it can overlap in time. Our models illustrate that several distinct mechanisms can account for Type II functional responses frequently seen in herbivores. We show how differences among these mechanisms can explain anomalies in the empirical literature on regulation of intake rate of mammalian herbivores including divergence in functional responses between grazers and browsers, linear functional response curves, and curves showing zero slope throughout the domain of food availability.