A drink of water can improve or impair mental performance depending on small differences in thirst.
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Adult↗
Biomedical subjects
P J Rogers
Publications and source records attributed to P J Rogers.
Dietary restraint and addictive behaviors: the generalizability of Tiffany's cue reactivity model.
UNLABELLED: Two studies are presented, which examine cue reactivity in dieting. METHODS: Experiment 1 investigated whether the presence of a preferred food affected dieters' performance on measures of attention, reaction time, and motor speed. The manipulation did not affect the performance. Experiment 2 investigated the performance of dieters (N = 19), highly restrained non-dieters (N = 18) and low-to-medium restrained eaters (N = 34) on two simple reaction time tasks. Subjects were either required to imagine their favorite food or to imagine their favorite holiday while completing a reaction time task. RESULTS: In the food condition, both dieters and restrained nondieters displayed significantly slower reaction times during the first three of five blocks of the task than the low-to-medium restrained eaters. CONCLUSIONS: The results are discussed in terms of Tiffany's (Psychological Review 97:147-168, 1990) model of cue reactivity in that different abstinent states produce comparable effects upon performance.
Adolescent↗
Acquisition and extinction of flavour preferences conditioned by caffeine in humans.
Previous research has shown that moderate caffeine users develop a liking for the flavour of a novel caffeinated drink only if they experience this drink in a caffeine-deprived state. This study tested how sensitive these conditioned-flavour preferences are to subsequent changes in deprivation state and the continued presence or absence of caffeine. Thirty-six moderate caffeine consumers were given 4 training days during which they evaluated a novel flavoured caffeinated drink consumed mid-morning after 12 h caffeine deprivation. Subjects were then divided into four groups depending on whether or not they remained caffeine-deprived and whether the test drink continued to contain caffeine. They then re-evaluated the novel drink over a further 4 test days. As expected, liking for the test drink increased across the 4 training days, and this increased liking was maintained across the 4 test days in the group who continued to receive the caffeinated version of the drink in a caffeine-deprived state. Liking decreased in the test phase in the caffeine-deprived group who no longer received caffeine (extinction). It is surprising that both groups who were tested in a non-deprived state showed a marked decrease in liking on all 4 test days relative to the last training day. This implies that conditioned-flavour preferences may not be expressed in the absence of the relevant motivational state (caffeine deprivation). Together, these data suggest that flavour preferences conditioned by caffeine are very sensitive to changes in the contingent relationship between deprivation state and caffeine content of the drink.
Adult↗
Effects of low doses of caffeine on cognitive performance, mood and thirst in low and higher caffeine consumers.
RATIONALE: Caffeine is present in many widely consumed drinks and some foods. In the fairly extensive literature on the psychostimulant effects of caffeine, there are few dose-response studies and even fewer studies of the effects of doses of caffeine lower than 50 mg (the range of the amounts of caffeine contained in, for example, a typical serving of tea or cola). OBJECTIVE: This study measured the effects of 0, 12.5, 25, 50 and 100 mg caffeine on cognitive performance, mood and thirst in adults with low and moderate to high habitual caffeine intakes. METHODS: This was a double-blind, within-subjects study. Following overnight caffeine abstinence, participants (n=23) completed a test battery once before and three times after placebo or caffeine administration. The test battery consisted of two performance tests, a long duration simple reaction time task and a rapid visual information processing task, and a mood questionnaire (including also an item on thirst). RESULTS: Effects on performance and mood confirmed a psychostimulant action of caffeine. All doses of caffeine significantly affected cognitive performance, and the dose-response relationships for these effects were rather flat. The effects on performance were more marked in individuals with a higher level of habitual caffeine intake, whereas caffeine increased thirst only in low caffeine consumers. CONCLUSIONS: After overnight caffeine abstinence, caffeine can significantly affect cognitive performance, mood and thirst at doses within and even lower than the range of amounts of caffeine contained in a single serving of popular caffeine-containing drinks. Regular caffeine consumers appear to show substantial tolerance to the thirst-increasing but not to the performance and mood effects of caffeine.
Adolescent↗
Food craving and food "addiction": a critical review of the evidence from a biopsychosocial perspective.
Although certain commonalities exist between eating and drug use (mood effects, external cue-control of appetites, reinforcement, etc. ), it is argued that the vast majority of cases of (self-reported) food craving and food "addiction" should not be viewed as addictive behavior. An explanation is proposed that instead gives a prominent role to the psychological processes of ambivalence and attribution, operating together with normal mechanisms of appetite control, the hedonic effects of certain foods, and socially and culturally determined perceptions of appropriate intakes and uses of those foods. Ambivalence (e.g., "nice but naughty") about foods such as chocolate arises from the attitude that it is highly palatable but should be eaten with restraint. Attempts to restrict intake, however, cause the desire for chocolate to become more salient, an experience that is then labelled as a craving. This, together with a need to provide a reason for why resisting eating chocolate is difficult and sometimes fails, can, in turn, lead the individual to an explanation in terms of addiction (e.g., "chocoholism"). Moreishness ("causing a desire for more") occurs during, rather than preceding, an eating episode, and is experienced when the eater attempts to limit consumption before appetite for the food has been sated.
Affect↗
Effects of sweetness and energy in drinks on food intake following exercise.
Exercise is known to cause physiological changes that could affect the impact of nutrients on appetite control. This study was designed to assess the effect of drinks containing either sucrose or high-intensity sweeteners on food intake following exercise. Using a repeated-measures design, three drink conditions were employed: plain water (W), a low-energy drink sweetened with artificial sweeteners aspartame and acesulfame-K (L), and a high-energy, sucrose-sweetened drink (H). Following a period of challenging exercise (70% VO2 max for 50 min), subjects consumed freely from a particular drink before being offered a test meal at which energy and nutrient intakes were measured. The degree of pleasantness (palatability) of the drinks was also measured before and after exercise. At the test meal, energy intake following the artificially sweetened (L) drink was significantly greater than after water and the sucrose (H) drinks (p < 0.05). Compared with the artificially sweetened (L) drink, the high-energy (H) drink suppressed intake by approximately the energy contained in the drink itself. However, there was no difference between the water (W) and the sucrose (H) drink on test meal energy intake. When the net effects were compared (i.e., drink + test meal energy intake), total energy intake was significantly lower after the water (W) drink compared with the two sweet (L and H) drinks. The exercise period brought about changes in the perceived pleasantness of the water, but had no effect on either of the sweet drinks. The remarkably precise energy compensation demonstrated after the higher energy sucrose drink suggests that exercise may prime the system to respond sensitively to nutritional manipulations. The results may also have implications for the effect on short-term appetite control of different types of drinks used to quench thirst during and after exercise.
Adult↗
Eating habits and appetite control: a psychobiological perspective.
An individual's eating behaviour is shaped by factors ranging from economic conditions and cultural practices to biological influences. The physiological system controlling appetite appears to be adapted to solving the problem of an unevenness of food supply across time, and is fairly permissive in its response to undereating and overeating. Consequently, when food is abundant, the diet is energy dense and energy expenditure is low, there is a strong tendency to become obese (i.e. obesity is better viewed as due to a 'toxic' environment than to faulty physiological control of appetite). Under such conditions the most common method of avoiding obesity is through the cognitive control of eating. However, dietary restraint and dieting are demanding tasks, and are associated with psychological costs, including significant impairment of cognitive performance. Restraint is also prone to disinhibition, with the result that it can sometimes undermine eating control, even leading to the development of highly disordered eating patterns. In part, these difficulties are due to the self-perpetuating nature of dietary habits: for example, hunger tends to be diminished during strict unbroken dieting, but increased in individuals having a highly variable eating pattern (such as occurs when eating is frequently disinhibited). These features of appetite control provide both barriers and opportunities for changing behaviour. Accordingly, there is a need for future research to focus on the psycho-social factors and the dieting practices predicting successful eating and weight control, with the objective of identifying the actual cognitive and behavioural strategies used by the many dieters and restrained eaters who are able to achieve weight loss and maintain long-term weight stability.
Appetite Regulation↗
No effect of glucagon-like peptide-1 on short-term satiety and energy intake in man.
Centrally administered glucagon-like peptide-1 (GLP-1) inhibits feeding in fasted rats, but its role in human satiety has been largely unexplored. The present study investigated the effect of peripheral GLP-1 infusion on gastric emptying and satiety in man. Ten non-obese male subjects were infused in a randomized single-blind within-subject crossover study using saline infusion as control. They received either a GLP-1 infusion (1.2 pmol/kg per min) or a saline infusion for 1 h, at 18.00 hours. At 20 min after starting the infusion the gastric emptying of a 400 ml water load was measured. Subjects completed behavioural self-rating scales to assess hunger and satiety. After 40 min subjects were given a buffet meal ad libitum and their food intake was recorded. GLP-1 infusion raised circulating GLP-1 concentrations to approximately twice those seen following a meal. It did not affect circulating insulin levels but caused a small fall in glucose levels. Gastric emptying of the water load was significantly delayed by the GLP-1 infusion. Energy intake from the buffet was unaffected by GLP-1 infusion. Self-assessment of hunger and satiety was similarly unaffected by the infusion before the buffet meal, although subjects tended to be less hungry after the buffet meal following GLP-1 infusion (P < 0.09). GLP-1 infusion delayed gastric emptying but had a minimal effect on food intake and satiety. This study casts doubts on whether GLP-1 is a major satiety factor in man, although a raised circulating plasma glucose level, as would normally occur postprandially, might be necessary for GLP-1 to increase satiety.
Adult↗
Hyperphagia in pre-fed rats following oral delta9-THC.
Using a pre-feed paradigm, the effects of orally-administered delta9-tetrahydrocannabinol (THC) on low baseline levels of nocturnal feeding were assessed. Following 2-h access to a palatable wet mash diet at dark onset, adult male Lister hooded rats (Charles River) were treated with either sesame seed oil vehicle or delta9- tetrahydrocannabinol (0.063, 0.12, 0.25, 0.5, 1.0, or 2.0 mg/kg). One hour later, rats were allowed ad libitum access to standard chow, and intakes were monitored over the subsequent 24 h. Doses of 0.5, 1.0, and 2.0 mg/kg produced substantial hyperphagia during the first hour of testing. Subsequently, rats compensated for their overconsumption so that 24-h intakes were similar in all conditions. The data confirm anecdotal reports of the orexigenic actions of exogenous cannabinoids and suggest a critical role for endogenous cannabinoid systems in the regulation of appetite.
Administration, Oral↗
An investigation of satiety in ageing, dementia, and hyperphagia.
OBJECTIVE: To investigate satiety in young, middle-aged, and elderly healthy adults, and in nonhyperphagic and hyperphagic elderly people with dementia. Previous work suggested hyperphagia in dementia was due to increased hunger and absence of satiation. METHODS: The primary measure of satiety was the amount of food eaten in an ad libitum meal, given 1 hr after a fixed preload. Three types of preload were used, high- and low-energy milkshakes and water. The effect of age was investigated by comparing the three groups of healthy adults. The effect of dementia was investigated by comparing the two demented groups with healthy elderly. RESULTS: Measurements suggested that accuracy of compensation for preload energy differences decreased with age and was absent in people with dementia. DISCUSSION: Lack of compensatory response in the elderly, particularly those with dementia, indicates the need for monitoring food intake to prevent over- or undereating.
Adult↗
Appetite changes under free-living conditions during Ramadan fasting.
During the fasting month of Ramadan, Muslims abstain from food and drink from sunrise until sunset. This change of eating pattern provides an opportunity to investigate factors controlling hunger and thirst. A group of healthy Muslims (15 men and 26 women) living in Reading, U.K. made hourly ratings of their hunger, mood and thirst, and recorded their food and drink intake on specified days before, during and after Ramadan between January and March 1996. There were no significant changes in body weight over Ramadan. Rated hunger increased substantially during the daily fast, and hunger was higher for the women than the men during the earlier days of Ramadan, whereas later, on average, fasting levels of hunger were very similar for both sexes (significant gender x day interaction,p<0. 001). During Ramadan, the men tended to spend much of their time away from home, and may therefore have largely avoided eating-related cues during the daily fast. The women, however, were frequently involved in preparing food to be eaten later after sunset, which suggests an explanation for the results based on the external cue control of hunger. That is, unreinforced exposure to food cues in this context may have led to a decrease in the capacity of these cues to stimulate hunger.
Adult↗
Conditioned flavour preference negatively reinforced by caffeine in human volunteers.
This study examined whether 100 mg caffeine could reinforce preference for the flavour of a novel drink in moderate caffeine users, both after overnight caffeine abstinence and 2 h after receiving 100 mg caffeine, using a two-stage between-groups procedure with 36 volunteers. In the first stage, liking for a test drink (fruit tea) was assessed at breakfast following overnight caffeine abstinence, with half the subjects receiving caffeine. Liking for the tea increased significantly over four trials for subjects receiving caffeine, and decreased significantly in those without caffeine. These effects were greatest in subjects who rated the drink as highly novel. In stage two, subjects evaluated a second drink (fruit-juice) 2 h after receiving the tea, and again half the subjects received caffeine Those subjects who received caffeine in stage two but not stage one showed a significant increase in liking for the fruit-juice over the 4 test days, whereas subjects who did not receive caffeine at either stage showed a progressive decrease in liking for this drink. In contrast, no significant change in liking for the fruit-juice was seen at stage two for subjects who had received caffeine in stage one, regardless of the presence or absence of caffeine at stage two. Caffeine at breakfast increased ratings of energetic and lively, and energetic ratings also increased following caffeine in the fruit-juice in subjects who had not had caffeine at breakfast. Overall, these data are consistent with a negative reinforcement model of caffeine reinforcement, and demonstrate further the utility of the conditioned flavour preference method for evaluating reinforcing effects of drugs in humans.
Adult↗
Regular caffeine consumption: a balance of adverse and beneficial effects for mood and psychomotor performance.
It has often been pointed out that caffeine is the most widely "used" psychoactive substance in the world, and accordingly, there is a very large amount of research available on the effects of caffeine on body and mind. In particular, a psychostimulant action of caffeine is generally accepted as well established; for example, caffeine has been found to quicken reaction time and enhance vigilance performance, and to increase self-rated alertness and improve mood. There is, however, a real difficulty in determining the net effects of caffeine. In a typical experiment the subjects have a history of regular caffeine consumption, and they are tested on caffeine and a placebo after a period of caffeine deprivation (often overnight). The problem with relying solely on this approach is that it leaves open the question as to whether the results obtained are due to beneficial effects of caffeine or to deleterious effects of caffeine deprivation. The present article briefly reviews this evidence on the psychostimulant effects of caffeine, and presents some new data testing the hypothesis that caffeine may enhance cognitive performance to a greater extent in older adults than in young adults. No age-related differences in the effects of caffeine on psychomotor performance were found. We conclude that overall there is little unequivocal evidence to show that regular caffeine use is likely to substantially benefit mood or performance. Indeed, one of the significant factors motivating caffeine consumption appears to be "withdrawal relief."
Adult↗
Impairments in working memory associated with spontaneous dieting behaviour.
BACKGROUND: The current study investigated the fundamental nature of the cognitive processing deficit that has been demonstrated to be associated with dieting to lose weight. Previous work has characterized this deficit as being primarily one of a reduction in working-memory capacity. The present study investigated the particular components of the working-memory system affected during dieting. METHOD: A sample of female subjects was classified as either low/medium restrained eaters (N = 34), highly restrained eaters (N = 18) or current dieters (N = 19), based on their responses to a modified version of the Dutch Eating Behaviour Questionnaire (DEBQ). Each subject completed tasks that assessed the Visuo-Spatial Sketchpad (mental rotation), Phonological Loop (effect of phonological similarity on recall) and the Central Executive (Tower of London Task) components of working memory. RESULTS: Those subjects who reported themselves to be currently dieting displayed poorer recall on the Phonological Loop task and slower planning times on the Tower of London Task. Performance on both these tasks correlated significantly with a self-report measure of body shape concern. CONCLUSIONS: These results support the hypothesis that the mediating variable in this deficit is that of preoccupying cognitions concerning food and body shape.
Adolescent↗
Mood and psychomotor performance effects of the first, but not of subsequent, cup-of-coffee equivalent doses of caffeine consumed after overnight caffeine abstinence.
Moderate caffeine consumers (n = 64, mean caffeine intake 453 mg/day) were deprived of caffeine overnight and semi-randomly allocated to four treatment groups, designated PPP, CPP, CCP and CCC, where P is placebo and C is caffeine (1.2 mg/kg, giving an amount of caffeine similar to that consumed in a serving of ground coffee). Caffeine or placebo (i.e. no caffeine) were administered double-blind in novel fruit juice drinks at 10:15, 11:30 and 13:00 h on the test day. Before (baseline), and 45 min after each of these times the participants completed a mood questionnaire and begun psychomotor performance tests lasting 25 min (1-min tapping task, and a long-duration simple reaction time task (SRT). Caffeine significantly increased energetic mood and improved psychomotor performance relative to placebo. Caffeine had particularly marked effects on SRT performance, ameliorating the slowing of performance with time on task and removing the post-lunch dip in performance. However, the three caffeine treatments, CPP, CCP and CCC, were equally effective. That is, mood and performance were improved to the same extent by one, two and three spaced doses (totalling 86, 172 and 258 mg) of caffeine. This result is consistent with previous findings indicating a flat dose-response relationship for the psychoactive effects of caffeine; and because of the adverse effects (e.g. fatigue) associated with overnight caffeine deprivation, it suggests that there is little net benefit to be gained from frequent caffeine use. At the very least, it appears that the psychostimulant effects of caffeine cannot on their own account for the typical pattern of consumption of caffeine-containing drinks.
Adolescent↗
Thermodynamic significance of the lactate gradient.
The theory that some bacteria can save energy by an energy-recycling process, in which protons are excreted with metabolic end-products with variable stoichiometry, has been examined by 1H-NMR. A method has been developed that utilises observed differences in the Hahn T2 relaxation of metabolites in the intracellular and extracellular compartments to distinguish and quantify metabolite signals originating from both compartments. It was found that the lactate electrochemical-potential gradient calculated from the fraction of lactate that is sufficiently mobile to contribute to the NMR signal was in exact balance with the proton electrochemical-potential gradient over a wide range of pH values. The conclusion was reached that previous reports of variable stoichiometry were due to 'bound' lactate at high intracellular pH that could neither contribute neither to the NMR signal nor to the lactate electrochemical-potential gradient.
Enterococcus faecalis↗
Impaired color naming of food and body shape words: weight phobia or distinct affective state?
OBJECTIVE: The current study investigated whether a concern with body shape and weight represents a distinct affective state, or whether it is better conceptualized as a highly specific form of anxiety. METHOD: The color-naming performance of women with a high Drive for Thinness score was examined under three experimental conditions: when a photograph of chocolate was present, when actual chocolate was present, and a control condition. High Drive for Thinness subjects demonstrated relatively impaired color naming of body shape words in the picture condition, but not in the food or control conditions. RESULTS: Although there was a significant impairment in the color naming of food words, this was unaffected by condition or degree of Drive for Thinness. DISCUSSION: The results are interpreted as supporting an analogy between weight/body shape concerns and subclinical phobic anxiety.
Adolescent↗
The effects of food deprivation and incentive motivation on blood glucose levels and cognitive function.
The current study investigated the relationships between blood glucose levels, mild food deprivation, sympathetic arousal, and cognitive processing efficiency. Subjects (n = 82) were randomly assigned to four experimental conditions, comprising combined manipulations of food deprivation and incentive motivation. Baseline and mid-session measurements of blood glucose, blood pressure and pulse rate were taken. Subjects completed a number of measures of cognitive processing efficiency and self report measures of affective and somatic state. Although glucose levels were lowered following food deprivation, there was no significant detrimental effect of food deprivation on task performance. However, improved recognition memory processing times were associated with deprivation. Incentive motivation was associated with faster simple reaction times and higher diastolic blood pressure. There were no significant relationships between glucose levels and task performance, further supporting the hypothesis that the brain is relatively invulnerable to short food deprivation.
Adolescent↗