Signal-detection analysis of recognition memory of obese subjects

Obese and normal-weight subjects were run on a series of recognition-memory tasks with low and high meaningful CVC trigrams. Subjects received feedback or no feedback regarding the appropriateness of their answers during testing for recognition memory. A signal-detection analysis was used to examine a relatively pure index of memory (d') as compared to response-bias factors [Ln (beta)]. No significant main effect on memory of obese and control subjects was noted although a significant interaction indicated that obese subjects' memory increases over trials in a differential fashion from normal-weight individuals with poorer performance among the obese after 3 trials. Feedback facilitated memory for both groups. Analysis of response criteria [Ln (beta)] showed no significant difference between groups. Highly meaningful trigrams had a significantly lower response criterion than low meaningful trigrams and there was a significant interaction of meaningfulness by trials. An interaction of feedback by meaningfulness was also present. Advantages of using a signal-detection analysis in memory studies comparing obese and normal weight subjects are discussed. Ramifications of the present data for the internality/externality hypothesis of obesity are also discussed.     

The restraint scale: a psychometric investigation

The psychometric characteristics of the Restraint Scale in obese and normal-weight subjects were compared. Scores were significantly higher and more homogeneous in the obese than in the normal-weight group. In light of previous studies indicating that obese subjects behave like normal-weight subjects whose Restraint scores are several points (approx. 3–6) lower, the present result was interpreted as suggesting that numerically-equivalent scores may represent less restraint in obese individuals than in normal-weight people.The psychometric evaluation of the Restraint Scale also revealed that the scale was less reliable in the obese than in the normal-weight population and seemed to tap somewhat different constructs in the two subpopulations. Factor analyses yielded a two-dimensional solution in the normal-weight group and a four-dimensional solution in the obese group. Correlations of the scale with a measure of Defensiveness also differed in the two samples.These results indicate that the norms, reliability and construct validity of the scale differ for obese and normal-weight populations. If restraint theory's predictions concerning the relations between restraint and obesity are to be adequately tested these differences must be taken into account.     

Intrameal eating patterns of obese and nonobese humans.

Two experiments were conducted to test whether the intrameal eating patterns of obese and normal-weight human subjects are different. The first experiment was conducted in a laboratory under the pretense of a taste test. Eating was observed and data were compiled for seven parameters related to eating. The second experiment was conducted under field-study conditions with the subjects unaware of their participation. Few statistically significant differences in eating behavior were observed between obese and normal-weight subjects. These results are in contrast to the majority of previous work.     

Application of virtual reality graphics in assessment of concussion.

Abnormal balance in individuals suffering from traumatic brain injury (TBI) has been documented in numerous recent studies. However, specific mechanisms causing balance deficits have not been systematically examined. This paper demonstrated the destabilizing effect of visual field motion, induced by virtual reality graphics in concussed individuals but not in normal controls. Fifty five student-athletes at risk for concussion participated in this study prior to injury and 10 of these subjects who suffered MTBI were tested again on day 3, day 10, and day 30 after the incident. Postural responses to visual field motion were recorded using a virtual reality (VR) environment in conjunction with balance (AMTI force plate) and motion tracking (Flock of Birds) technologies. Two experimental conditions were introduced where subjects passively viewed VR scenes or actively manipulated the visual field motion. Long-lasting destabilizing effects of visual field motion were revealed, although subjects were asymptomatic when standard balance tests were introduced. The findings demonstrate that advanced VR technology may detect residual symptoms of concussion at least 30 days post-injury.     

The effects of acute stress and pubertal development on metabolic hormones in the rat

A dramatic change in stress responsiveness occurs during pubertal development such that stress-induced corticosterone secretion in prepubertal animals takes 45-60 min longer to return to baseline compared to adults. Though corticosterone is known to influence energy mobilization, it is presently unknown whether stressors affect other hormones important in energy utilization and metabolism differentially in animals before and after pubertal development. Therefore, we exposed prepubertal (28 days of age) and adult (77 days of age) male rats to a single 30 min session of restraint stress in either the light or dark phase of the animals' light-dark (LD) cycle and measured plasma glucose, insulin and thyroid hormones (thyroxine (T4) and triiodothyronine (T3)). We found similar stress-induced increases in plasma glucose levels in prepubertal and adult animals in the LD phase of the LD cycle. We also found that prepubertal animals have lower circulating insulin and total and free T4 levels, but higher total and free T3 levels compared to adults in both the light and dark phases (LD). Interestingly, insulin and thyroid hormone levels were unaffected by acute stress at either age or time of day. These data indicate that, despite prepubertal animals showing an extended glucocorticoid stress response after a single acute exposure to stress, glucose levels are similarly affected by acute stress in prepubertal and adult animals. Furthermore, though stage of development significantly affects the levels of peripheral metabolic hormones such as insulin, T4 and T3, acute stress does not appreciably influence their secretion before or after puberty.     

Sexual Outcasts: The Perceived Impact of Body Weight and Gender on Sexuality1

A person's weight may be perceived as an important aspect of his or her sexuality and a significant determinant of his or her interpersonal sexual experiences. However, researchers interested in body weight and sexuality have focused exclusively on sexual disorders found in individuals with eating disorders; consequently, little is known about people's beliefs about weight and sexuality, despite the individual and interpersonal significance of such beliefs. Undergraduates received information about a male or female, obese or normal-weight stimulus person and then evaluated that person along several dimensions related to sexuality. Participants believed that an obese man's sexual experiences would be highly similar to those of a normal-weight man. However, participants viewed an obese woman as less sexually attractive, skilled, warm, and responsive, and perceived her as less likely to experience desire and various sexual behaviors than a normal-weight woman. In addition, participants believed that an obese woman was less sexually attractive, skilled, warm, and responsive than an obese man.     

Effects of dietary restraint, obesity, and gender on holiday eating behavior and weight gain

This investigation evaluated the impact of dietary restraint, relative weight, and gender on holiday eating behavior and weight gain. 65 Ss (31 men and 34 women) completed detailed food records for the 2 days before, the 4 days during, and the 2 days after the Thanksgiving weekend. Results indicated increased eating during the Thanksgiving holiday, with men eating more than women and the obese eating less than the nonobese. There was also a significant Total Restraint X Weight X Time interaction, with unrestrained normal-weight subjects behaving similarly to high-restrained overweight subjects over time. There was also a highly reliable Total Restraint X Sex X Time interaction. The most striking finding from this interaction was that high-restrained women displayed decreases in their dietary intake over time. Correlational analyses revealed that restraint scores were negatively associated with dietary intake over the 8-day period but were positively associated with weight gain. The implications for dieting, eating behavior, and energy balance are discussed.     

Subjective equality and just noticeable differences in body-size judgments by obese persons

Body-size estimates by obese and normal-weight subjects were compared using two different procedures with a TV-video methodology. In the continuous method subjects adjusted an image larger or smaller until they judged a correct TV-image had been achieved. In the second procedure the method of constant stimuli was used wherein values corresponding to the point of subjective equality (PSE) and difference threshold (DL) were determined. No differences between obese and normal-weight subjects were obtained with these procedures. On the continuous task subjects slightly underestimated body size and were more accurate on descending trials where they adjusted the size of the image downwards. With the second procedure, an average PSE of -.62% was obtained, with an average DL = 7.27%. Different PSE values were obtained when subjects were judging whether their image was distorted too wide or too thin. Data from the two procedures are compared and ramifications for the study of body size are discussed.     

Effect of swimming session duration and repetition on metabolic markers in rats

The aim of this study was to investigate the profile of metabolites in male rats subjected to 50-60 min of swimming on three protocols: group A, a single 50 min swimming session; group B, one session a day for three days (5 min on day 1, 15 min on day 2 and 30 min on day 3); and group C, one session a day for 5 days, with increasing duration from 5 min on day 1, 15, 30, 45 and 60 min on consecutive days. The interval between sessions was 24 h. Measurements were made after the last swimming session. Controls did not swim. The glycogen content of liver and gastrocnemius and soleus muscle was depleted in the three groups that swam, but blood glucose concentration was significantly increased only in group B. Serum lactate concentrations were greater than the controls in groups A and B. There were significant increases in serum free fatty acid concentrations in all groups that swam. The increases in plasma free fatty acids may have resulted from lipolysis stimulated by endogenous catecholamines in groups A and C, since basal lipolysis measured in vitro was unchanged by swimming. The large increase in basal lipolysis in group B may have contributed to the rise in plasma free fatty acids. Adipocytes from rats in groups A and B were supersensitive to epinephrine, whereas those from group C were not. We conclude that the metabolic alterations were less pronounced after the last of five swimming sessions over 5 days than after a single session, even though session duration and the contribution of the physical component were similar. Glucose mobilization, but probably not utilization, was similar in the three groups that swam. The mechanisms of lipid mobilization from adipose tissue differed, depending on the stress paradigm. The metabolic changes in groups A and B indicated that three daily swimming sessions were insufficient to cause adaptation. The results contrast with previous findings for foot-shock stress, which leads to sensitization rather than adaptation in response to repeated stimuli.     

Preliminary remarks on type of task and delay in children's prospective memory

This study investigated the extent to which the type of task influences children's prospective memory performance. 80 subjects, aged 7 to 11 yr. participated in an experiment in which the type of task (time-based vs event-based) and the retention interval (5 min. vs 10 min.) varied. The prospective memory task was embedded in a principal task lasting about 15 min. and required subjects perform an action at a given time or in response to a specific cue. Analysis indicated that the delay was associated with prospective memory performance only on a time-based task in which the intention has to be performed after 10 min. but not age. Analysis indicated also that time monitoring was associated with shorter latency between the target time and the execution of the intention on the time-based task. Implications were discussed.     

Implicit and explicit attitudes toward high-fat foods in obesity

This study examined implicit and explicit attitudes toward high-fat foods in obese (n = 30) and normal-weight controls (n = 31). The Implicit Association Test (A. G. Greenwald, D. E. McGee, & J. L. K. Schwartz, 1998) was used to measure the differential association of the 2 target categories--high-fat vs. low-fat food words--with an attribute dimension (positive vs. negative). Results suggest that obese people are characterized by a significantly stronger implicit negative attitude toward high-fat foods than are normal-weight controls. This implicit negative attitude is contradictory to their preferences and behavior: Several studies indicate that obese people prefer and consume high-fat foods. Apparently, obese people like the taste of high-fat foods but not the fat content itself, not only on the explicit but also on the implicit level.     

Stress, reactivity, and immune function in healthy men.

We examined the effects of acute psychological stress on lymphocyte proliferation and circulating levels of interleukin-1 and -2. Healthy men were exposed to two viewings of a gruesome surgery film and were asked to recall details of the film twice during a 30-min period. These subjects were compared to a nonstress control group. Lymphocyte proliferation to the mitogen concanavalin A (Con A; 5 micrograms/ml) was decreased during and after exposure to the stressor when compared to the control group. This decrease was more pronounced in subjects exhibiting greater blood pressure reactivity while viewing the film than in subjects showing smaller blood pressure responses. None of the other immunological measures was significantly affected by the stressor. Cortisol was not correlated with lymphocyte responsiveness. Possible explanations for these results and implications for further research are discussed.     

Level of object representation and psychic structure deficit in obese persons

The structural deficit and external regulation hypotheses of addiction state that addicts do not have adequate psychic structure with which to regulate painful affects internally. They instead use their drug of choice as an external regulator to self-medicate painful affects. This study tests whether the hypotheses can be applied to obese persons, for whom food may be the drug of choice. The level of object representation of 22 moderately obese and 24 normal weight subjects was compared using the Blatt Family Interaction Questionnaire. The mean level of object representation of both parents was lower for the obese subjects than for the normal-weight subjects. This finding supports the structural deficit and external regulation hypotheses of food addiction.     

Mental Health and Obesity: A Meta-Analysis

The relationship between obesity and psychological distress is not clear because research conducted so far is not conclusive, with some studies finding that obese people report less mental health than normal-weight individuals, whilst others find that obesity may work as a protective factor that prevents people with weight problems from developing mental health issues. In this meta-analysis we review research that compares the mental health (measured with SF-36) of class I obese people (Body Mass Index between 30 and 34.99) with normal weight people (Body Mass Index between 18 and 24.99) in non-clinical adult populations. The meta-analysis conducted assumed a random-effects model and a weighted mean effect size was calculated (d), together with its statistical significance and confidence interval. Results reveal that obese women report less mental health than normal weight females (d?=??.26) but that obese men show more mental health than normal weight individuals (d?=?.62). The results give support to the so-called “Jolly Fat” hypothesis.     

The role of automatic obesity stereotypes in real hiring discrimination

This study examined whether automatic stereotypes captured by the implicit association test (IAT) can predict real hiring discrimination against the obese. In an unobtrusive field experiment, job applications were sent to a large number of real job vacancies. The applications were matched on credentials but differed with respect to the applicant's weight. Discriminatory behavior was quantified by the extent to which the hiring managers invited normal-weight versus obese applicants to a job interview. Several months after the behavioral data were obtained, the hiring managers completed an obesity IAT and explicit hiring preference measures. Only the IAT scores reliably predicted interview decisions. More specifically, hiring managers holding more negative automatic stereotypes about the obese were less likely to invite an obese applicant for an interview. The present research is the first to show that automatic bias predicts labor market discrimination against obese individuals. Practical implications are discussed.     

Palatability of food as a factor influencing obese and normal-weight children''s eating habits

The type and amount of food leftover from school lunches by normal-weight and obese elementary school children was examined for its similarity to the pattern reported by Krassner et al. (1979) in a study of normal-weight and obese college students. In this study 102 observations of children between the ages of 9–11, were taken over eight lunch periods in their school cafeteria. Overall, the normal-weight children left only slightly more food uneaten than did the obese children. However, when food palatability was examined, it was found that normal-weight children left over twice as much palatable food as did obese children. Children did not differ on the amount of unpalatable food left uneaten.

These results suggest that Krassner et al.'s observation that obese adults leave less food on their plates may be extended to children and, further, that like obese adults, obese children may be more influenced by the palatability of food than their normal-weight peers.     

Moderate psychosocial stress appears not to impair recall of words learned 4 weeks prior to stress exposure

Recent studies in humans have reported that recall of previously learned material is especially sensitive to the disruptive effects of pharmacologically induced cortisol elevations. Whether similar effects occur after exposure to psychosocial stress remains to be shown. Moreover it is unknown whether stress before or after the initial learning interacts with the later effects of repeated stress on delayed recall (e.g. state-dependent learning). Forty subjects participated in the present experiment. They learned a word list either one hour before or 10 min after exposure to a psychosocial laboratory stressor. Delayed recall was tested 4 weeks later, again either before or after stress. Salivary cortisol levels increased significantly in response to both stress exposures. Stress had no effects on the initial learning and also did not impair delayed recall. Moreover there was no evidence for state-dependent learning. The current data seem to be in conflict with previous studies demonstrating that delayed recall is especially sensitive to elevated cortisol levels. Several reasons for these discrepancies are discussed. Among them is the small sample size, the moderate cortisol increase in response to the second stress exposure but also the long recall delay, which might lead to memory traces less susceptible to stress.     

Stress and blood glucose in type II diabetes mellitus

Six adults with non-insulin dependent diabetes mellitus participated in a laboratory procedure to determine the effects of an acute Stressor, mental arithmetic, on blood glucose, cardiovascular, and subjective indices of stress. They then completed 12 days home monitoring of stressful events, subjective stress, and blood glucose. Diet and activity were controlled to evaluate the direct effects of stress on blood glucose in the natural environment. Laboratory results showed significant increases in blood glucose, cardiovascular (HR and SBP), and subjective stress ratings during the mental arithmetic task when compared to a resting condition. Home monitoring data were consistent with the laboratory findings; blood glucose range tended to be greater on high vs low stress days, especially when the difference between high and low stress was greatest. These findings suggest that the laboratory stress induction procedure was externally valid and that in the natural environment, stress has a hyperglycemic effect on blood glucose.     

A comparison of obese and normal-weight families' sychological characteristics

Abstract

The present study assessed obese and normal-weight family members' perceptions of their nuclear family's social and environmental characteristics. Preliminary results support previous correlational and case studies that suggest obese families are dysfunctional. Results from the Family Environment Scale indicate that obese families perceive their family characteristics differently compared to normal-weight families or to a representative sample of families. Specifically, obese families perceive their homes as less cohesive, more conflictual, less interested in social and cultural activities, and less organized compared to normal-weight families. Obese parents also perceive themselves as more controlling and their families as less independent compared to nonobese parents.     

Fat, full, and happy: effects of food deprivation, external cues, and obesity on preference ratings, comsumption, and buying intentions.

This study reassesses the relative influence of internal and external cues on the behavior of obese and normal individuals. Specifically, the effects of external cues and food deprivation on preference ratings, consumption, and buying intentions were tested for overweight and normal subjects. Obese subjects were more reactive than normals to external cues as indicated by their eating more and intending to buy more food after viewing food slides as opposed to scenery slides. However, their behavior also changed in response to food deprivation, becoming more negative. The obese showed lower food consumption, lower buying intentions, and lower ratings of both food and nonfood slides in the empty condition compared to the full condition.