Effects of nutritional and mechanical properties of food on ruminative behavior.

Previous studies have identified a reliable relation between the quantity of food ingested and ruminating in profoundly retarded individuals and have established some parametric characteristics of this relation. The present study investigated three different properties of food that may influence this relation. Experiment 1 examined the role of stomach distention produced by including in the subject's diet wheat bran in amounts equivalent to and exceeding the calculated amount of crude fiber in the starch-satiation diet reported by Rast, Johnston, Drum, and Conrin (1981) and Rast, Johnston, and Drum (1984). There was a decrease in ruminating, although this decrease was smaller and more gradual than in the starch-satiation condition. Experiment 2 showed that increasing calories without increasing food volume resulted in a gradual and moderate decrease in ruminating. Experiment 3 replicated and extended the first two experiments by varying both caloric intake and stomach distention as well as oropharyngeal and esophageal stimulation in a different sequence of conditions. All variables exerted some control over responding. However, the large and immediate effects of the starch-satiation procedure occurred only when subjects were permitted to consume unlimited quantities.     

Recognition of food by individual, food-naive, weaning rats (Rattus norvegicus)

To control and observe first feeding experiences, pups were reared without access to food. At weaning age, individual pups received simultaneous access to a palatable, noncaloric diet and a similar diet containing starch. Each diet contained a flavor cue. Within 20 min of sampling both diets pups preferentially ingested the caloric alternative. Further tests indicated that pups learned a preference for flavor cues paired specifically with ingestion of starch. In caloric discrimination tests in which the diets were not distinguished by artificial flavors, pups did not show the rapid preference for the caloric diet seen in earlier experiments. We suggest that recognition and preference for the caloric diet is based on its rapid postingestive effects rather than readily preferred sensory features of the starch. Our findings demonstrate the abilities of individual, food-naive pups to rapidly recognize food and indicate a role for associative learning in the onset of independent feeding.     

Hyperphagia in rats with experimental diabetes mellitus: a response to a decreased supply of utilizable fuels

Alloxan-diabetic rats were hyperphagic when fed diets containing little fat, but they ate normal amounts of food when given diets rich in fat. Normal rats increased food intake to the same degree when the caloric density of their diet was decreased by reducing the content of fats or carbohydrates in isocaloric amounts. Diabetic rats did not respond substantially to changes in caloric density of their diet which were produced by altering the content of dietary carbohydrates, but they systematically increased food intake as the amount of fat in their diet was reduced. Diabetic rats ate normal amounts of a high-fat diet despite continued loss of nutrients in urine and persisting impairments in glucose utilization, fat storage, and liver glycogen deposition. These findings suggest that hyperphagia in experimental diabetes mellitus is a compensatory response to a lack of utiliziable fat fuels rather than the result of a metabolic disturbance per se.     

THE RELATION OF FOOD QUANTITY TO RUMINATION BEHAVIOR

Preliminary work suggested that the quantity of food ingested by retarded individuals who usually ruminated following meals was related to the frequency and duration of ruminating responses. This possible relation was experimentally examined by systematically varying food quantity from regular portions to satiation levels for three retarded individuals who exhibited high levels of ruminating. A clear functional relation of food quantity to ruminating emerged, with satiation procedures producing rapid and large decreases in the relatively high frequencies and durations of ruminating characteristic of baseline food quantity conditions.     

A seven year follow-up of treating rumination with dietary satiation

”Fred“, a man with profound mental retardation who was 24 years old at the beginning of this study, was referred for treatment of rumination. A number of minimally restrictive interventions, including administration of Zantac, extra fluids, and delivery of peanut butter after meals, had been used without success. In April of 1989 Fred began a satiation diet with ad libitum access to starchy foods or to fruits and vegetables, in addition to his regular meals. His baseline weight was 82 pounds and he ruminated during 58% of 10 s intervals measured during 20 min post-meal observations. During the first month of the satiation diet, Fred's ruminating declined to 6% of measured intervals, he consumed a mean of 163 fluid ounces of extra food per day, and his weight increased to 90 pounds. After 4 months' treatment, Fred's ruminating had declined to zero, his food consumption had stabilized at approximately 65 extra ounces of food per day, and his weight had stabilized at about 120 pounds. Starting in August 1990, in an effort to minimize weight gain, extra food was limited to 50% of Fred's ad libitum food consumption (averaged over the previous 6 weeks). Fred's weight gradually declined to about 100 pounds with zero rumination over the next two years. In August 1992 Fred's ruminating accelerated to 17% of intervals and he was again offered ad libitum food access. Over the next 7 months, rumination declined to zero and his weight increased slightly to about 105 pounds. This study shows that rumination that had not responded to less restrictive procedures was suppressed for 7 years via dietary satiation. Although dietary satiation is not without some risk, Fred has suffered no adverse effects from the procedure, other than gaining approximately one-third of his baseline weight. © 1997 John Wiley & Sons, Ltd.     

The nature of the association between diet and serum lipids in the community: a twin study.

Diet is commonly thought to be an environmental influence on serum lipid concentrations. This study evaluated whether total caloric and fat intake predict total cholesterol (TC), low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), and triglyceride (TRIG) concentrations for environmental, as compared with genetic, reasons among 137 monozygotic and 67 dizygotic young adult twins. When genetic influences were controlled by correlating differences between monozygotic co-twins, a significant association remained between diet and TC, LDL, and HDL, suggesting that these dietary and serum lipid measures correlate for environmental reasons. Twin structural equation modeling confirmed these results. Overall, these results provide additional support for the hypothesis that diet is an environmental influence on TC, LDL, and HDL.     

The effects of gender and response style on depressed mood

Research has shown that gender differences in the rate of depression may be accounted for by different response styles. To examine whether response style affects mood, depressed mood was induced in 31 females and 33 males (all Caucasian) who were then randomly assigned to either a ruminating or a distracting response task. The findings supported the response style theory as the ruminating group remained depressed after the response task, while the distracting group became less depressed. Gender was not a factor in this experiment as both men and women reacted similarly to the mood induction and the experimental tasks. Although clinical implication cannot be determined from a study involving nondepressed subjects, it can be concluded that ruminating about one's depressed mood is not an effective method for overcoming depression.     

A parametric analysis of the relationship between food quantity and rumination

Rumination is the chronic regurgitation, chewing, and reswallowing of previously ingested food. The study reported here, using a parametric design, examined the control of rumination by the quantity of food eaten at meals. The subjects were three profoundly retarded individuals who chronically emitted this behavior. The quantity of food by weight ingested daily was varied in 10-oz steps in both ascending and descending series (data were collected only after breakfasts and lunches). Ruminating decreased when food quantity increased and increased when food quantity decreased. In addition, there was a similar inverse interaction between breakfast food quantity and post-lunch ruminating. The data showed relatively rapid transitions in both frequency and duration at each meal size for all subjects. The data establish a clear functional relation between the quantity of food ingested and ruminating.     

Self-forgiveness and forgiveness-seeking in response to rumination: Cardiac and emotional responses of transgressors

Self-forgiveness and forgiveness-seeking are important and understudied aspects of forgiveness. We examined the cardiac and emotional patterns of healthy young adults (40 women, 40 men) who recalled an unresolved offense they had caused another person. Participants engaged in four imagery conditions: ruminating about the offense, being humbly repentant and engaging in self-forgiveness, seeking forgiveness from the victim and receiving forgiveness, and seeking forgiveness from the victim and being begrudged. Being repentant and begrudged forgiveness by one’s victim was associated with the same level of guilt as when ruminating, but significantly more negative emotion, less control, and less empathy than when ruminating, self-forgiving, and receiving forgiveness from the victim. Compared to ruminating about one’s wrongdoing, self-forgiving alleviated guilt and negative emotion, increased perceived control, decreased heart rate, and increased parasympathetic activation. Imagery of receiving forgiveness from the victim resulted in these same patterns and was equivalent to self-forgiveness across variables.     

Perceptions of women related to food choice

Male and female subjects (predominately white) provided impression ratings of body shape, personality traits, and total caloric consumption for a female target based on her preference for a low fat or high fat diet. Results showed that meal type significantly affected impression ratings: the target who preferred low fat foods was viewed more favorably than the one who preferred high fat fare. Compared with male subjects, female subjects perceived the target who preferred a high fat diet to be significantly less conscientious. Males were significantly more accurate than females in their caloric estimations of targets' total daily consumption. The results will be discussed in terms of the social pressure on women to restrict not only their weight to acceptable levels, but their food consumption as well.Portions of this paper were presented at the meeting of the Eastern Psychological Association, Providence, Rhode Island, April 14–17, 1994.The authors wish to thank Justina Bradley, Loraina Ghiraldi, and two anonymous reviewers for their thoughtful comments on an earlier version of this paper. Melissa Van Brocklin's help during the data collection was also greatly appreciated.     

An experimental test of the effect of weight-loss dieting on bulimic pathology: tipping the scales in a different direction

Although it is widely accepted that dieting increases the risk for bulimic pathology, this hypothesis has not been tested in a randomized experiment. Accordingly, the authors conducted an experimental test of the dietary restraint model by randomly assigning nonobese women (N = 82) to either a 6-week, low-calorie diet or a waitlist control condition. The diet intervention resulted in significant weight loss, confirming that dieting was successfully manipulated. Contrary to the restraint model, dieting resulted in significant decreases in bulimic symptoms relative to the control condition. Results converge with past findings from randomized obesity prevention and treatment trials and provide evidence that dieting does not promote bulimic pathology; rather, effective decreases in caloric intake appear to reduce bulimic symptoms.     

The Effects of Food and Gender on Interpersonal Perceptions

Male and female subjects provided ratings of personal traits, femininity and masculinity, and total caloric consumption for a female or a male target based on the type of diet she or he had allegedly consumed. The gender associated with the foods presented for each dietary profile was manipulated. Results showed that Target Gender and Dietary Profile significantly affected impression ratings and calorie estimates. Both male and female subjects perceived male eaters and those who ate a feminine diet more favorably. Results are discussed in terms of the different underlying expectations held for males and females when food consumption is involved during the impression formation process.     

Some effects of thiamine deficiency and reduced caloric intake on “behaviour under stress” and on learning

The main purpose of the investigation was to determine the effects of thiamine deficiency in rats on behaviour under stress and on learning. Since thiamine deficiency reduces food intake, it was necessary to have two control groups. The first received adequate thiamine, but a food intake reduced to that of the vitamin-deficient animals; the second received adequate thiamine and an unrestricted food intake. It was thus possible to study the effects both of thiamine deficiency and of reduced caloric intake on the behaviour variables measured.

The experimental group was maintained on a thiamine-deficient diet throughout the entire experimental period. Because of the effects of thiamine deficiency on caloric intake, food-hunger was never used as a form of motivation. Behaviour in four different situations was studied: in Hall's open-field test, in two discrimination situations both involving exposure to insoluble and soluble problems, and in a water maze.

Contrary to the findings of several previous studies, there were no significant effects of thiamine deficiency on behaviour prior to the onset of polyneuritis with its debilitating effects on motor co-ordination. There was also no evidence of impairment in any of the behaviour studied which could be attributed to restrictions in caloric intake. This was the case even though the restrictions continued for a period of somewhat more than twelve months. Although these restrictions did not lead to impairment they were associated with certain changes in performance. Animals whose feeding was restricted were more active and, during the soluble phase of one discrimination situation, showed more vicarious trial and error and learned more readily than animals fed ad libitum on the same diet. It is suggested that these differences may be interpreted in terms of the effects of what previous investigators have referred to as “irrelevant drives”.     

Cooling core body temperature may slow down neurodegeneration

Reduction of core body temperature has been proposed to contribute to the increased lifespan and the anti-aging effects conferred by caloric restriction in mice and higher primates. Cooler biologically compatible core body temperatures have also been hypothesized to combat neurodegenerative disorders. Yet, validation of these hypotheses has been difficult until recently, when it demonstrated that transgenic mice engineered to have chronic low core body temperature have longer lifespan independent of alteration in diet or caloric restriction. This article reviews the literature and highlights the potential influence of core body temperature's governing role on aging and in the pathophysiology of neurodegenerative disorders in humans. What makes recent findings more significant for humans is the existence of several methods to lower and maintain low core body temperatures in human subjects. The therapeutic potential of "cooler people" may also raise the possibility that this could reverse the adverse-health consequences of elevations in core body temperature.     

Effects of a short-term exercise program on caloric consumption

The present study investigated the effects of a short-term exercise program on caloric intake. Thirty-three women were randomly assigned to either a high-intensity exercise group (80% maximum heart rate), low-intensity exercise group (55% maximum heart rate), or waiting list control group. Exercisers were required to ride ergometer bicycles three times per week for 7 weeks, expending 200 kilocalories of energy per exercise session. All participants recorded food intake during specified weeks before, during, and following the exercise program. Results showed no significant caloric intake differences among the three groups, but a trend toward reduction in food intake with increased exercise intensity was found. Interestingly, comparisons between caloric intake on exercise and nonexercise days revealed that both exercise groups consumed significantly less on exercise days. Additionally, the control group evidenced a larger caloric intake level than did the two exercise groups on exercise days. These results suggest that exercisers do not compensate for energy expenditure by increasing caloric intake and that choosing between low- and high-intensity exercise does not differentially alter caloric intake. Nevertheless, maximization of negative energy balance or weight loss may be best achieved by exercise programs of high frequency and intensity.     

Caloric balancing and sucrose intake of hamsters and gerbils

In Experiment 1, hamsters and gerbils were randomly assigned to groups that were given a choice between pairs of sucrose solutions differing in concentration. The groups consisted of a control along with the following pairs: 2% and 6%; 2% and 8%; 2% and 12%; 2% and 18%; 6% and 8%; 6% and 12%; 6% and 18%; 12% and 18%. They were tested for 15 days, and the results indicated that the animals drank more from the cylinder containing the higher concentration. The principle of "least consummatory effort" appeared to be substantiated by these results. In Experiment 2, other hamsters and gerbils were randomly assigned to one of six groups receiving either 0.5%, 2%, 6%, 10%, 14%, or 18% sucrose solution. Analysis of their intake of sucrose and Purina Lab Chow indicated that their total caloric intake was relatively constant, reflecting the fact that an increase of consumption of the solutes in the sucrose solution reduced their intake of the stock diet. The results from both experiments indicated that although the caloric intake of hamsters relative to body weight was greater than that of gerbils, the proportion of total calories taken from sucrose was greater for the latter than for the former.     

Beyond one work day? A daily diary study on causal and reverse effects between experienced workplace incivility and behaving rude towards others

In this diary study with N = 348 employees, we examine whether the contagion effect of workplace incivility transfers beyond one work day that is whether the experience of workplace incivility is related to showing rude behaviours towards others the next day. Additionally, we examine whether ruminating in the evening of a work day and building an intention for revenge behaviour mediate this relationship, and explore whether a serial mediation process exists where experienced incivility triggers ruminative thoughts, which, in turn, increase the likelihood of intending to act, which transfers into actual rude behaviour the next day. Using a multilevel path analysis, our results confirmed a lagged relationship between workplace incivility one day and rude behaviours towards others the next day. Between-persons’ workplace incivility was also related to showing rude behaviour towards others. Neither rumination nor revenge behaviour intent proved to be mediators of this relationship. Additionally, the serial mediation process was not confirmed; however, parts of the process—namely the relationship between experienced workplace incivility and ruminating about work in the evening—received support. Importantly, the reverse relationship (i.e., showing rude behaviour one day leads to experiencing workplace incivility the next) was not supported in our analysis. By adding a new, daily time perspective, our study suggests that participants do not intentionally provoke episodes of incivility, but rather react to others’ incivility.     

Rats defend different body weights depending on palatability and accessibility of their food.

Normal adult rats lived on powdered diets adulterated to contain as much as 1.6% quinine sulfate, on a palatable high-fat diet, or in Skinner boxes with 45-mg Noyes pellets available on fixed-ratio (FR) schedules as high as FR 156. They maintained lower body weights over periods of months in proportion to the percentage of quinine adulteration or the fixed ratio. Rats exposed to the high-fat diet overate as much and gained weight as rapidly as rats recovering from food deprivation, and became moderately obese. Rats having become lean or obese contingent on the palatability or accessibility of their diet defended body weight by eating more in the cold, less when force-fed by gavage, and more to restore weight after food deprivation. Yet on chow they restored and defended body weights typical of rats whose diet had been confined to commercially prepared chow. These results are interpreted to be inconsistent with motivational models that rigidly distinguish drive from incentive, that treat body weight changes as evidence for failure to regulate energy balance or body weight, or that rely exclusively on deprivation of food or reduction of body weight for definitions of need for calories. Instead, caloric homeostasis in rats may incorporate ecological constraints.     

Biased perception of overeating in bulimia nervosa and compulsive binge eaters

This study investigated the relationship between caloric intake and perceived overeating in subjects with and without a history of problematic binge eating. Eighty subjects (20 in four groups: bulimia nervosa, compulsive binge eaters, obese, and normal controls) self-monitored eating for 2 weeks. The regression slopes for self-reported overeating as a function of caloric intake were contrasted across the four groups. At higher caloric levels, bulimics and binge eaters reported overeating at a significantly higher rate compared to obese and normal control groups. These data were interpreted as a type of cognitive bias whereby subjects with a history of binge eating distorted their perception of overeating at progressively higher caloric levels. It was proposed that excessive concern about eating and dieting may cause such cognitive biases. A parallel was drawn with body image distortion, which appears to be associated with overconcem with body size and shape.