Cognitive restraint and sensitivity to cues for hunger and satiety

‘When hunger makes everything better looking!’: The effect of hunger on the aesthetic appreciation of human bodies, faces and objects

Background

Research evidence suggests that physiological state of hunger might affect preference for female body weight, such that hungrier, compared to satiate, men prefer heavier body weight and rate as more attractive heavier female figures. Here, we seek to extend these findings by comparing the effects of fasting and snack on aesthetics judgements of the bodies and faces of conspecifics and of objects in a sample of female and male participants.

Methods

Forty-four participants (women: n = 21, mean age = 23.70 yrs ± 0.62) provided aesthetic liking judgments of round and slim human bodies, faces and objects, under at least 12 h of overnight fasting and immediately after having eaten a snack (i.e., bananas). An anthropometric measure of adiposity (i.e., Body Mass Index, BMI) was also collected from each observer.

Results

Overall, we found that participants’ aesthetic judgements were higher for slim stimuli compared to round ones. However, after fasting, participants rated round stimuli as more attractive compared to when they had a snack. This hunger-based shift in ratings not only was apparent when stimuli depicted a human body or face, but also when they depicted an object, thus suggesting a general modification of observers’ aesthetic preference related to hunger. Importantly, this effect was modulated by participants’ BMI so that only participants with a high BMI provided higher aesthetic judgements for round stimuli after fasting than after a snack.

Conclusions

Our results demonstrated that both the modification of the physiological state and the individual differences in adiposity level of the observers might affect the aesthetic appreciation of the external world.

Ingested but not perceived: Response to satiety cues disrupted by perceptual load

Selective attention research has shown that when perceptual demand is high, unattended sensory information is filtered out at early stages of processing. We investigated for the first time whether the sensory and nutrient cues associated with becoming full (satiety) would be filtered out in a similar manner. One-hundred and twenty participants consumed either a low-satiety (75 kcal) or high-satiety (272 kcal plus thicker texture) beverage, delivered via an intra-oral infusion device while participants simultaneously completed a task which was either low or high in perceptual demand. Among participants who performed the low perceptual load task, ingestion of the high-satiety beverage increased rated satiety and reduced consumption at a subsequent snack test. However, both effects were eliminated by the high perceptual load task. Therefore, the processing of satiety cues was dependent on the availability of attention, identifying a novel perceptual load mechanism of inattentive eating and supporting more recent cognitive models of appetite control.

Examining the association between body trust and body mass index with quantile regression

PURPOSE

Schachter's externality theory posits a connection between the inability to eat according to internal cues and higher body mass index (BMI); however, related work has not investigated associations between body trust and the wide range of BMIs found in general samples. This study examined the association between body trust and BMI across levels of BMI to determine whether this relationship differed as a function of BMI level.

METHODS

Participants were 534 adults (55.4% female), mean age 36 years, BMIs 15.13-67.90 (M = 27.89, SD = 7.25), recruited via MTurk. They completed self-report assessments of body trust, height, and weight. Quantile regression was utilized to estimate effects of body trust on BMI at five equidistant quantiles of BMI.

RESULTS

Overall linear regression analyses indicated that body trust was significantly negatively associated with BMI. Quantile regression revealed a significant negative relationship at each quantile of BMI, and Wald tests indicated the association was significantly stronger at the 0.7 and 0.9 quantiles than at the 0.1, 0.3, and 0.5 quantiles, which did not differ.

CONCLUSIONS

Quantile regression identified a stronger relationship between body trust and BMI at 0.7 and 0.9 quantiles than at 0.1, 0.3, and 0.5 quantiles of BMI. Results align with the externality hypothesis, which suggests those at higher weights experience difficulty using internal cues to guide eating. A weaker-than-expected association between body trust and low BMI may be due to restricted range (few low-BMI participants). Replication in eating disorder samples is merited.

LEVEL OF EVIDENCE

Level V, cross-sectional descriptive study.

Effect of a High-Protein, High-Fiber Beverage Preload on Subjective Appetite Ratings and Subsequent Ad Libitum Energy Intake in Overweight Men and Women: A Randomized, Double-Blind Placebo-Controlled, Crossover Study

BACKGROUND

Dietary protein and fiber have been shown to independently improve subjective measures of appetite control.

OBJECTIVE

The aim of this study was to determine the acute effects of a high-protein, high-fiber (HP/HFb) beverage taken as a preload compared with an isocaloric lower-protein, lower-fiber (LP/LFb) placebo beverage on subjective appetite ratings and subsequent energy intake at an ad libitum meal in healthy adults.

METHODS

A total of 50 overweight/obese men and women [n = 25 men, 25 women; age 30 ± 2 y; body mass index (BMI) 29.6 ± 0.3 kg/m2] received a 160 kcal HP/HFb beverage containing 17 g protein and 6 g fiber on one occasion and an isocaloric LP/LFb placebo beverage containing 1 g protein and 3 g fiber on another occasion in a randomized, double-blind, crossover design. Thirty min after consumption of the beverage preload, an ad libitum pizza meal was provided to be consumed over a 30-min period. Visual analog scales (VAS) were used to assess subjective appetite ratings throughout the testing period. The Revised Restraint Scale (RRS) was used to classify participants as restrained or unrestrained eaters.

RESULTS

HP/HFb led to greater reductions in postprandial desire to eat and hunger compared with LP/LFb (both, P < 0.05) but did not significantly affect postprandial fullness or prospective food consumption. Subsequent meal energy intake tended to be lower after HP/HFb compared with LP/LFb (P = 0.09). A subanalysis showed lower energy intake after HP/HFb in older participants (≥25 y) compared with LP/LFb, which was not observed in the younger participants (<25 y).

CONCLUSIONS

Compared with LP/LFb, a HP/HFb beverage preload reduced hunger, desire to eat, and tended to reduce subsequent food intake. Dietary restraint and age appear to influence subsequent energy intake and should be taken into account when designing nutrition interventions for weight reduction and/or maintenance. This trial was registered at clinicaltrials.gov as NCT02979717.

Knowing too much: Knowledge of energy content prevents liking change through flavour-nutrient associations

Associations between flavours and the consequences of ingestion can lead to changes in flavour liking depending on nutrient content, an example of flavour-nutrient learning (FNL). Expectations about the consequences of ingestion can be modified by information at the point of ingestion, such as nutritional labelling. What is unknown is the extent to which these label-based expectations modify FNL. Since nutrient information can alter expectations about how filling a product would be, we hypothesised that labels predicting higher energy (HE) content would enhance satiety and so promote more rapid flavour learning. To test this, participants consumed either a lower energy (LE: 164 kcal) or HE (330 kcal) yoghurt breakfast on four separate days, either with no product label or with labels displaying either the actual energy content (Congruent label) or inaccurate energy (Incongruent label). Participants rated liking on all four days: on Days 1 and 4, they could also consume as much as they liked, but consumed a fixed amount (300 g) on Days 2 and 3. Both liking and intake increased with exposure in the HE, and decreased in the LE, condition when unlabelled in line with FNL. In contrast, no significant changes were seen in either the Congruent or Incongruent label conditions. Contrary to predictions, these data suggest that FNL occurs when there is an absence of explicit expectations of actual nutrient content, with both accurate and inaccurate information on nutrient content disrupting learning.

Applied Interventions in the Prevention and Treatment of Obesity Through the Research of Professor Jane Wardle

PURPOSE OF REVIEW

Obesity presents a challenge for practitioners, policy makers, researchers and for those with obesity themselves. This review focuses on psychological approaches to its management and prevention in children and adults.

RECENT FINDINGS

Through exploring the work of the late Professor Jane Wardle, we look at the earliest behavioural treatment approaches and how psychological theory has been used to develop more contemporary approaches, for example incorporating genetic feedback and habit formation theory into interventions. We also explore how Jane has challenged thinking about the causal pathways of obesity in relation to eating behaviour. Beyond academic work, Jane was an advocate of developing interventions which had real-world applications. Therefore, we discuss how she not only developed new interventions but also made these widely available and the charity that she established.

Distraction, restrained eating and disinhibition: An experimental study of food intake and the impact of ‘eating on the go’

To assess the impact of distraction on subsequent eating, 60 females consumed a cereal bar while watching TV, walking or talking, and their subsequent desire to eat and food intake were assessed. No effects were found for desire to eat. But while those higher in restrained eating consumed less overall and fewer calories after watching TV or talking, they consumed more overall and more calories (specifically five times more chocolate) if the cereal bar was eaten while walking. ‘Eating on the go’ may disinhibit restrained eaters either as a form of distraction or by offering a justification to overeat.

Evaluating the Impact of U.S. Food and Drug Administration–Proposed Nutrition Facts Label Changes on Young Adults’ Visual Attention and Purchase Intentions

Background. The U.S. Food and Drug Administration (FDA) has proposed modifying the Nutrition Facts Label (NFL) on food packages to increase consumer attention to this resource and to promote healthier dietary choices. Aims. The present study sought to determine whether the proposed NFL changes will affect consumer attention to the NFL or purchase intentions. Method. This study compared purchase intentions (yes/no responses to “would you purchase this food?” for 64 products) and attention to NFLs (measured via high-speed eye-tracking camera) among 155 young adults randomly assigned to view products with existing versus modified NFLs. Attention to all individual components of the NFL (e.g., calories, fats, sugars) were analyzed separately to assess the impact of each proposed NFL modification on attention to that region. Data were collected in 2014; analysis was conducted in 2015. Results. Modified NFLs did not elicit significantly more visual attention or lead to more healthful purchase intentions than did existing NFLs. Relocating the percent daily value component from the right side of the NFL to the left side, as proposed by the FDA, actually reduced participants’ attention to this information. The proposed “added sugars” component was viewed on at least one label by a majority (58%) of participants. Discussion. Results suggest that the proposed NFL changes may not achieve FDA’s goals. Changes to nutrition labeling may need to take a different form to meaningfully influence dietary behavior. Conclusion. Young adults’ visual attention and purchase intentions do not appear to be meaningfully affected by the proposed NFL modifications.

Influence of Nutrition Claims on Appetite Sensations according to Sex, Weight Status, and Restrained Eating

Nutrition claims may help people to adopt healthier eating habits, but little is known about the potential cognitive effects of such claims on appetite sensations. The main purpose of this study was to evaluate the impact of nutrition claims and individual factors on perceived appetite sensations. According to a three ("healthy" versus "diet" (i.e., satiating) versus "hedonic") by two (restrained or not restrained) by two (normal-weight or overweight/obese) by two (men versus women) factorial design, 164 males and 188 females aged 18-65 were invited to taste an oatmeal-raisin snack in a blinded and ad libitum context. Visual analog scales (150 mm) were used to evaluate appetite sensations before and over 1 h after consumption period. BMI and Restraint Scale were used to categorize participants according to their weight and restraint status. No main condition effect was observed for any of the four appetite sensations. However, subgroups analysis revealed significant differences among specific subgroups. A main effect of sex was also observed for all appetite sensations with men reporting higher levels of desire to eat, hunger and prospective food consumption, and lower levels of fullness than women. These findings highlight the importance of considering individual characteristics in interaction when studying appetite sensations.

The addictive dimensionality of obesity

Our brains are hardwired to respond and seek immediate rewards. Thus, it is not surprising that many people overeat, which in some can result in obesity, whereas others take drugs, which in some can result in addiction. Though food intake and body weight are under homeostatic regulation, when highly palatable food is available, the ability to resist the urge to eat hinges on self-control. There is no homeostatic regulator to check the intake of drugs (including alcohol); thus, regulation of drug consumption is mostly driven by self-control or unwanted effects (i.e., sedation for alcohol). Disruption in both the neurobiological processes that underlie sensitivity to reward and those that underlie inhibitory control can lead to compulsive food intake in some individuals and compulsive drug intake in others. There is increasing evidence that disruption of energy homeostasis can affect the reward circuitry and that overconsumption of rewarding food can lead to changes in the reward circuitry that result in compulsive food intake akin to the phenotype seen with addiction. Addiction research has produced new evidence that hints at significant commonalities between the neural substrates underlying the disease of addiction and at least some forms of obesity. This recognition has spurred a healthy debate to try and ascertain the extent to which these complex and dimensional disorders overlap and whether or not a deeper understanding of the crosstalk between the homeostatic and reward systems will usher in unique opportunities for prevention and treatment of both obesity and drug addiction.

Obesity and addiction: neurobiological overlaps

Drug addiction and obesity appear to share several properties. Both can be defined as disorders in which the saliency of a specific type of reward (food or drug) becomes exaggerated relative to, and at the expense of others rewards. Both drugs and food have powerful reinforcing effects, which are in part mediated by abrupt dopamine increases in the brain reward centres. The abrupt dopamine increases, in vulnerable individuals, can override the brain's homeostatic control mechanisms. These parallels have generated interest in understanding the shared vulnerabilities between addiction and obesity. Predictably, they also engendered a heated debate. Specifically, brain imaging studies are beginning to uncover common features between these two conditions and delineate some of the overlapping brain circuits whose dysfunctions may underlie the observed deficits. The combined results suggest that both obese and drug-addicted individuals suffer from impairments in dopaminergic pathways that regulate neuronal systems associated not only with reward sensitivity and incentive motivation, but also with conditioning, self-control, stress reactivity and interoceptive awareness. In parallel, studies are also delineating differences between them that centre on the key role that peripheral signals involved with homeostatic control exert on food intake. Here, we focus on the shared neurobiological substrates of obesity and addiction.

Imaging of brain dopamine pathways: implications for understanding obesity

Obesity is typically associated with abnormal eating behaviors. Brain imaging studies in humans implicate the involvement of dopamine (DA)-modulated circuits in pathologic eating behavior(s). Food cues increase striatal extracellular DA, providing evidence for the involvement of DA in the nonhedonic motivational properties of food. Food cues also increase metabolism in the orbitofrontal cortex indicating the association of this region with the motivation for food consumption. Similar to drug-addicted subjects, striatal DA D2 receptor availability is reduced in obese subjects, which may predispose obese subjects to seek food as a means to temporarily compensate for understimulated reward circuits. Decreased DA D2 receptors in the obese subjects are also associated with decreased metabolism in prefrontal regions involved in inhibitory control, which may underlie their inability to control food intake. Gastric stimulation in obese subjects activates cortical and limbic regions involved with self-control, motivation, and memory. These brain regions are also activated during drug craving in drug-addicted subjects. Obese subjects have increased metabolism in the somatosensory cortex, which suggests an enhanced sensitivity to the sensory properties of food. The reduction in DA D2 receptors in obese subjects coupled with the enhanced sensitivity to food palatability could make food their most salient reinforcer putting them at risk for compulsive eating and obesity. The results from these studies suggest that multiple but similar brain circuits are disrupted in obesity and drug addiction and suggest that strategies aimed at improving DA function might be beneficial in the treatment and prevention of obesity.

Food and drug reward: overlapping circuits in human obesity and addiction

Both drug addiction and obesity can be defined as disorders in which the saliency value of one type of reward (drugs and food, respectively) becomes abnormally enhanced relative to, and at the expense of others. This model is consistent with the fact that both drugs and food have powerful reinforcing effects-partly mediated by dopamine increases in the limbic system-that, under certain circumstances or in vulnerable individuals, could overwhelm the brain's homeostatic control mechanisms. Such parallels have generated significant interest in understanding the shared vulnerabilities and trajectories between addiction and obesity. Now, brain imaging discoveries have started to uncover common features between these two conditions and to delineate some of the overlapping brain circuits whose dysfunctions may explain stereotypic and related behavioral deficits in human subjects. These results suggest that both obese and drug-addicted individuals suffer from impairments in dopaminergic pathways that regulate neuronal systems associated not only with reward sensitivity and incentive motivation, but also with conditioning (memory/learning), impulse control (behavioural inhibition), stress reactivity, and interoceptive awareness. Here, we integrate findings predominantly derived from positron emission tomography that shed light on the role of dopamine in drug addiction and in obesity, and propose an updated working model to help identify treatment strategies that may benefit both of these conditions.

'Expected satiety' changes hunger and fullness in the inter-meal interval

Previously, we have shown that foods differ markedly in the satiety that they are expected to confer (compared calorie-for-calorie). In the present study we tested the hypothesis that 'expected satiety' plays a causal role in the satiety that is experienced after a food has been consumed. Before lunch, participants (N=32) were shown the ingredients of a fruit smoothie. Half were shown a small portion of fruit and half were shown a large portion. Participants then assessed the expected satiety of the smoothie and provided appetite ratings, before, and for three hours after its consumption. As anticipated, expected satiety was significantly higher in the 'large portion' condition. Moreover, and consistent with our hypothesis, participants reported significantly less hunger and significantly greater fullness in the large-portion condition. Importantly, this effect endured throughout the test period (for three hours). Together, these findings confirm previous reports indicating that beliefs and expectations can have marked effects on satiety and they show that this effect can persist well into the inter-meal interval. Potential explanations are discussed, including the prospect that satiety is moderated by memories of expected satiety that are encoded around the time that a meal is consumed.

Low dopamine striatal D2 receptors are associated with prefrontal metabolism in obese subjects: possible contributing factors

Dopamine's role in inhibitory control is well recognized and its disruption may contribute to behavioral disorders of discontrol such as obesity. However, the mechanism by which impaired dopamine neurotransmission interferes with inhibitory control is poorly understood. We had previously documented a reduction in dopamine D2 receptors in morbidly obese subjects. To assess if the reductions in dopamine D2 receptors were associated with activity in prefrontal brain regions implicated in inhibitory control we assessed the relationship between dopamine D2 receptor availability in striatum with brain glucose metabolism (marker of brain function) in ten morbidly obese subjects (BMI>40 kg/m(2)) and compared it to that in twelve non-obese controls. PET was used with [(11)C]raclopride to assess D2 receptors and with [(18)F]FDG to assess regional brain glucose metabolism. In obese subjects striatal D2 receptor availability was lower than controls and was positively correlated with metabolism in dorsolateral prefrontal, medial orbitofrontal, anterior cingulate gyrus and somatosensory cortices. In controls correlations with prefrontal metabolism were not significant but comparisons with those in obese subjects were not significant, which does not permit to ascribe the associations as unique to obesity. The associations between striatal D2 receptors and prefrontal metabolism in obese subjects suggest that decreases in striatal D2 receptors could contribute to overeating via their modulation of striatal prefrontal pathways, which participate in inhibitory control and salience attribution. The association between striatal D2 receptors and metabolism in somatosensory cortices (regions that process palatability) could underlie one of the mechanisms through which dopamine regulates the reinforcing properties of food.

Effects of exercise and restrained eating behaviour on appetite control

Obesity is a global epidemic; increased consumption of energy-dense food and reduced physical activity levels are likely to be the main drivers. Previous cross-sectional research has shown that sedentary males, unlike their active counterparts, are unable to compensate for previous energy intake (EI). Using a longitudinal design a 6-week exercise intervention was found to improve short-term appetite control, leading to a more ‘sensitive’ eating behaviour in response to previous EI, both acutely at a test meal and for the next 24 h. Although the mechanisms whereby acute and chronic exercise improves short-term appetite remain unknown, post-ingestive satiety peptides are likely to be involved. Acute exercise was found to increase postprandial levels of polypeptide YY, glucagon-like peptide-1 and pancreatic polypeptide but to have no impact on ghrelin, suggesting that exercise can trigger physiological changes in satiety hormone secretion that could help in appetite control and weight maintenance. In the context of an increased availability of highly-palatable food, dietary restraint may be increasingly important. Although restraint has been associated with abnormal eating behaviour, in the laboratory no counter-regulation was found in restrained eaters when presented with a buffet meal 60 min after a high-energy preload or when a pasta-meal was presented 3 h after preloading. Although restraint was not found to impact on polypeptide YY or TAG, lower postprandial glucose and insulin plasma levels were observed in restrained eaters, together with increased feelings of fullness. In conclusion, short-term appetite control seems to be favourably modified by exercise, while the impact of restraint on appetite seems to be more complex.

Vulnerability to freshman weight gain as a function of dietary restraint and residence

Although many studies have found that students gain weight during their first year at college, many others have not. Participants in the present study were classified according to their scores on the Herman/Polivy Restraint Scale and their place of residence-at home or on campus. Body weight was assessed early in the academic year and five months later. At the same sessions participants completed a questionnaire pertaining to their eating habits prior to beginning college (first session) and since coming to college (second session). Overall weight gain was 1.5 kg; those most likely to gain weight were restrained eaters living on campus, who gained an average of 4.1 kg. In addition, changes in eating habits were a significant independent predictor of weight gain.

Smoking status relationships with the food and fluid intakes of free-living humans

OBJECTIVE

The relation of cigarette smoking to food and fluid intakes was studied.

METHODS

Ninety-nine smoking and 551 non-smoking free-living adult humans provided a detailed record of their eating and drinking in 7-d diaries.

RESULTS

Cigarette smoking was associated with significant changes in overall intakes and meal pattern. Smokers had higher intakes of fluids in the form of drinks due to higher levels of alcohol and coffee/tea consumption. Smokers were less hungry but more responsive to social facilitation and time of day. There were also substantial gender differences in smoking relations to intake, with male smokers tending to have higher overall and meal intakes particularly of fats than non-smokers, whereas female smokers tended to have lower overall intakes, fewer meals, and lower amounts of carbohydrates than non-smokers. Male smokers tended to be less responsive to their before-meal stomach content, their level of hunger, and the palatability of the meal than non-smokers, whereas females tend to be more responsive to all of these influences on meal size.

CONCLUSION

These results suggest that smoking has very few direct simple effects on intake but rather influences intake indirectly through its covariation with alcohol and caffeine intakes and with dietary restraint and that smoking has different, sometimes opposite, influences in males and females.

Novel calcium-gelled, alginate-pectin beverage reduced energy intake in nondieting overweight and obese women: interactions with dietary restraint status

BACKGROUND

Foods containing strong-gelling fibers may provide a safe and efficacious strategy for reducing food intake by stimulating endogenous satiety signaling.

OBJECTIVE

A novel, 2-part beverage, consisting of alginate-pectin and calcium components, that forms a stable, fibrous gel in the stomach was tested to determine its effects on subjective satiety and food intake in overweight and obese women.

DESIGN

The investigation was a within-subjects, double-blind, placebo-controlled study. Subjects (n = 29) ingested a 2-part beverage twice per day (once before breakfast and once midafternoon) for 7 d. Three alginate-pectin formulations were tested: 1.0 g, 2.8 g, and control (no fiber). Subjective satiety and ad libitum food intake were measured on days 1 and 7 of each 1-wk treatment period with a 1-wk washout between testings.

RESULTS

A significant reduction in food intake was observed at dinner for both formulations compared with the control formulation. The effects of the gel beverage differed as a function of rigid dietary restraint status. Women in the lower 50th percentile of rigid restraint consumed 12% less energy during the day and 22% less for the evening snack in the 2.8-g condition compared with the control condition. No effect was found for women in the upper 50th percentile of rigid restraint.

CONCLUSIONS

Consumption of a postingestion, calcium-gelled fiber beverage twice daily reduced energy intake in overweight and obese women with low rigid restraint scores. Use of foods designed to enhance satiety may be an effective adjunctive therapy for weight loss; however, more research is needed to determine how dietary restraint alters this response.

The influence of restrained and external eating patterns on overeating

Eating in response to an increasingly obesogenic environment has been strongly implicated as a salient aspect of eating behaviour, arguably influenced by learning and experience. Interindividual differences in susceptibility to weight gain may be due, in part, to variability in response to environmental triggers. The phenomenon of food craving may also be an important factor influencing appetite control. The present study tested a model, in which food craving was hypothesised to be an intervening causal variable, on a causal pathway between responsivity to environmental cues and the development of obesity. One hundred and twenty four participants (aged 21-71 years, 83 females and 41 males) completed the study. Participants completed the Dutch eating behaviour questionnaire (DEBQ), measuring external eating (externality), emotional eating (emotionality) and restrained eating behaviour (restraint), and an adapted form of the food craving inventory (FCI), assessing cravings for carbohydrate, fats, sweets and fast food fats, in addition to total food cravings. Initial analysis showed positive correlations between FCI-tot and body mass index (BMI), FCI-fats and BMI and FCI-fast food fats and BMI in both men and women, and between FCI-carbohydrates and BMI in men only. Multiple regression analyses showed externality as the principal predictor of food craving, which was greater in males compared to females, but differential for different food groups between genders. Restrained eating and cravings for fats and fast food fats were negatively associated in women only. As predicted, total cravings, and cravings for fats and fast food foods mediated the positive association between external eating and BMI. It is concluded that appetitive response to external cues as an important risk factor in appetite control is mediated through cravings for particular food groups and is gender-dependent.

Effect of exposure to a forbidden food on eating in restrained and unrestrained women

OBJECTIVE

The current study explored the effect of availability of a forbidden food on subsequent eating behavior in restrained and unrestrained women.

METHOD

Thirty restrained and 30 unrestrained, normal-weight women were assigned randomly to one of two conditions, an experimental group that was exposed to a forbidden food (chocolate) for 24hr or a control group that was given no special intervention. At the end of the exposure period, all subjects completed an intake test of the forbidden food.

RESULTS

Although subjects were instructed not to eat the food provided for the exposure period, women in the restrained group consumed a small quantity of the chocolate, whereas unrestrained women consumed none. Intake at test was greater in the temptation than in the control condition and restrained eaters consumed more than unrestrained eaters in both conditions.

DISCUSSION

The results are discussed in terms of current theories of restrained eating and the possible interrelationships between eating regulation and cognition.

NPY attenuates positive cortical DC-potential shift upon food intake in man

Previous studies have shown that the regulation of hunger and satiety is accompanied by coordinate changes in cortical excitability. Starved subjects show a transient negative shift in the scalp-recorded cortical direct current (DC-)potential in the beginning of eating, indicating increased cortical excitability. With increasing satiety, the DC negativity becomes soon replaced by a reward related positive potential shift. Neuropeptide Y (NPY) is known from animal studies to increase food intake and induce weight gain, which might result from increasing hunger drive or reducing satiety. Here we investigated whether NPY affects the cortical sequelae of hunger and satiety regulation as reflected by cortical DC-potentials in man. DC-potentials were recorded over frontal (Fz, F3, F4), central (Cz, C3, C4) and parietal (Pz, P3, P4) electrode positions in 14 subjects who had abstained from eating for 15 h and who were intranasally administered 50 nmol of NPY and placebo 20 min prior to recordings. After a 3-min baseline epoch, subjects consumed 400 ml of liquid food within 5 min. Recordings ended 7 min after food consumption. In the placebo condition during food intake, with some delay a positive DC-potential shift developed which was most pronounced over frontal and central areas and reached maximum values 0-3 min after food consumption. NPY reduced this satiation associated positive shift (p<0.05) over all areas except P3 and Pz. Data suggest that NPY exerts its orexigenic influence by attenuating mechanisms of satiation.

Effect of moderate intensity exercise on acute energy intake in normal and overweight females

The purpose of this study is to determine the impact of moderate intensity exercise on acute post-exercise energy intake (EI) in normal and overweight females. Twelve normal weight (BMI<25), and 12 over weight (BMI>25) inactive women (mean age 35+/-8) participated in a 2-day experimental study. On the exercise day, participants were asked to walk on a treadmill at 60% maximum heart rate for 1h. After the exercise, participants selected and ate food at a university cafeteria. Post-exercise EI was compared to a non-exercise day. A single mixed model repeated 2 x 2 ANOVA was used to determine the impact of exercise on post-exercise EI. The overweight women consumed significantly more (p<0.02) than the normal weight women on both experimental days and there was a significant (p<0.03) difference in fat intake. The higher post -exercise EI of the overweight group may have been due to the energy needs associated with a higher BMI but it is also possible that cognitive factors, food availability and environment may influence post-exercise EI.

Does nutrition information about the energy density of meals affect food intake in normal-weight women?

This study investigated whether the energy density of foods affected energy intake when subjects were informed about the energy density of their meals. Forty normal-weight women ate breakfast, lunch, and dinner in the laboratory on three separate days. The entrée at each meal was varied in energy density to be either 1.25, 1.50, or 1.75 kcal/g (5.23, 6.28, or 7.32 kJ/g), but was held similar in macronutrient composition and palatability. On each day, the entrées at all three meals had the same energy density. All entrées were consumed ad libitum. Subjects were assigned to one of two groups. Subjects in the information group received a nutrition label with each meal, which showed the energy density of the entrée. Subjects in the no-information group did not receive any nutrition information. The results revealed that subjects in both groups had the same pattern of food intake across the three levels of energy density. Energy density significantly affected energy intake; subjects in both groups combined consumed 22% less energy in the condition of low energy density than in the condition of high energy density (p < 0.0001). These findings show that energy density can have a significant influence on energy intake, even when individuals are informed about the energy density of their meals.

Dietary energy density and weight regulation

Dietary energy density (ED) has been suggested as an important determinant of energy intake and, therefore, energy regulation. This review summarizes published studies on the effects of dietary ED on hunger, satiety, energy intake, and body weight in healthy individuals, and compares the relative effects of ED manipulated by dietary fat only, fat and fiber, water, and type of sweetener. In short-term studies, consumption of low-ED foods promotes satiety, reduces hunger, and decreases energy intake with no marked differences between different dietary manipulations used to change ED. In addition, low-ED diets promote moderate weight loss in long-term studies. In studies lasting longer than 6 months, weight loss was more than three times as great in individuals consuming diets both low in fat and high in fiber compared with diets only low in fat (-3.4 kg versus -1.0 kg). Combined, these studies suggest that diets low in fat and high in fiber may be the most effective low-ED diets for promoting weight loss. Further research is needed on the effects of dietary ED by changing water or sweetener content.

Effects of food attributes on hunger and food intake

OBJECTIVE

To explore the relative importance of a food's macronutrient composition, energy value, energy density, fiber content, weight, volume, sensory properties and rheology on hunger and food intake.

DESIGN

Preloads of peanuts, peanut butter (rheology control), almonds (tree nut), chestnuts (macronutrient control), chocolate (sensory control), rice cakes (volume control), pickles (weight control) and no load (time control) were consumed by subjects in random order at weekly intervals and hunger was assessed over the subsequent 180 min. Free-feeding energy and macronutrient intake were monitored 24 h before and following preload ingestion.

SUBJECTS

Twelve male and 12 female healthy, normal weight (12-28% body fat), adults (mean (s.d.) age 22 +/- 2.5 y) with low dietary restraint.

RESULTS

Hunger ratings following consumption of the 2092 kJ (500 kcal) preloads of peanuts, peanut butter, almonds, chestnuts and chocolate were significantly lower than the low energy preloads or no preload condition, but with the exception of peanut butter, did not vary from each other. The rate of hunger recovery was consistent across all preloads so the overall impact of each food on hunger was determined by the initial drop it evoked. Total energy, but not macronutrient, compensation was observed with all preloads. Consequently, the fatty acid profile of the total diet reflected the composition of the preloads.

CONCLUSIONS

Energy content may be the primary determinant of a food's impact on hunger. Because macronutrient compensation is weak, a dietary supplement or substitute may influence the daily dietary nutrient profile.

A psychodynamic hypothesis on the night eating syndrome

The Night Eating Syndrome (NES) is usually interpreted in organicistic and physiological terms. This paper looks at it dynamically in terms of the psychic dimension of the patient through an examination of the contrasting tensions (emptiness and fullness; saving and destroying the object, etc.) that are the unconscious cause of his NES. A relationship is suggested between nocturnal reawakenings as a form of eating behaviour and the undreamt or avoided dreams used by the patient as a defence against "perception" of the unconscious.

Effect of replacement of fat by nonabsorbable fat (sucrose polyester) in meals or snacks as a function of dietary restraint

The effect of replacement of fat by nonabsorbable fat on energy intake and on feelings of hunger and satiety was assessed, in normal-weight dietary-restrained (n = 11), dietary-unrestrained (n = 13) and in postobese dietary-restrained women (n = 12), using 2 experimental designs. First, during breakfast and lunch on 2 sequential weekdays, 23 g of dietary fat was replaced by 23 g of a nonabsorbable fat. Second, dietary fat was replaced by a nonabsorbable fat in snacks consumed ad lib during a different week. Fat replacement in meals or in snacks did not result in changes in hunger and satiety ratings throughout the day. Replacement in meals yielded an energy intake reduction of 0.5 MJ/day (not significant) in dietary-unrestrained and in postobese dietary-restrained subjects; this reduction included 44% energy intake compensation. In normal-weight dietary-restrained subjects, energy intake reduction of 0.7 (p < 0.05) MJ/day was observed; this reduction included 22% energy intake compensation. Moreover, fat replacement in meals showed a shift in macronutrient composition from 35-40% energy from fat to 31-32% energy from fat. Replacement in snacks yielded an energy intake reduction of 0.4-0.5 MJ/day (not significant) in normal-weight dietary-restrained subjects and a reduction of 0.6-0.7 (p < 0.05) MJ/day in dietary-unrestrained and in postobese dietary-restrained subjects. In this situation, energy intake from snacks consisted of 48-78% energy from reduced-fat reduced-energy snacks, which implied a replacement of 10-15 g fat by 10-15 g SPE (sucrose polyester) and a shift in macronutrient composition from 35-40 percentage energy from fat to 33-36 percentage energy from fat. These results suggest short-term beneficial effects of fat replacement on energy and fat intake.

Effects of a 2-day abstinence from smoking on dietary, cognitive, subjective, and physiologic parameters among younger and older female smokers

In a field study, dietary intakes, subjective ratings of well-being, cognitive performance, blood pressure, and heart rate were assessed during 6 days of ad libitum smoking and 2 days without smoking by using an electronic diary. The subjects were 59 younger and older female smokers, aged 25-35 and 55-65 years, respectively. Smoking abstinence significantly lowered heart rate, blood pressure, and saliva cotinine levels, indicating a good compliance by the subjects. Smoking abstinence was also followed by subjectively reported decreased levels of relaxation and activity and by higher levels of sleepiness, negative strain, and craving for smoking. Mental performance as assessed with the Stroop task was not affected by smoking abstinence. Whereas the percentage distribution of the macronutrients did not change with smoking abstinence, the intake of total energy increased significantly by 182 kcal/day. Main effects of age were found on some of the dietary parameters and Stroop performance variables only. A post hoc analysis revealed a significant influence of the employment status factor on the excess caloric intake and the increased frequency of sweet consumption when under abstinence. These increases were significantly greater in nonemployed (housewives, jobless) than in working women. Further correlational analysis revealed strong relations between caloric intake and simultaneous craving for smoking and food during abstinence but not during nonabstinence days, whereas no relation between caloric intakes and saliva cotinine or respiratory carbon monoxide were obtained. These findings suggest that the availability of food products and subjective withdrawal symptoms are probably more important moderators of increased dietary intake following smoking cessation than any pharmacologic systemic effects of nicotine.

Information about the fat content of preloads influences energy intake in healthy women

OBJECTIVE

This study tested the hypothesis that the perceived fat content of a preload (a required first course) influences subsequent food and energy intake.

SUBJECTS AND DESIGN

Forty-eight healthy, nondieting women (24 restrained, 24 unrestrained) were given a fixed amount (350 g) of three different yogurts (low-fat, low-calorie; low-fat, high-calorie; high-fat, high-calorie), or no yogurt, followed by lunch (30 minutes after the yogurt preload was served) and dinner (4.5 hours later). Each subject was tested in all four conditions in a counterbalanced design. Half of the subjects received accurate information, in the form of a label, about the fat content of the yogurts, which did not necessarily correspond to energy content; the other half received no information.

ANALYSES

Energy intake, the percentage of macronutrients in the meals, and subjective sensations of hunger and satiety were analyzed.

RESULTS

No effect of restraint was noted in the intake analyses. A significant information-by-preload interaction (P < .05) was found. Subjects who had information consumed more energy at lunch after eating a preload labeled low fat than after eating a preload with similar energy content but labeled high fat. The opposite response was seen in women who did not receive information. When energy consumed at dinner was included in the analyses, overall intake was still significantly greater in the women who received information and ate a low-fat preload. No differences were found in the percentage of macronutrients selected or in subjective sensations after consumption of any of the preloads.

CONCLUSIONS

Messages about the fat content of a food can influence energy intake in healthy women.