Human obesity, dieting, and anticipatory salivation to food

Orthonasal olfactory influences on consumer food behaviour

It is often suggested in the popular press that food chains deliberately introduce enticing product aromas into (and in the immediate vicinity of) their premises in order to attract customers. However, despite the widespread use of odours in the field of sensory marketing, laboratory research suggests that their effectiveness in modulating people's food behaviours depends on a range of contextual factors. Given the evidence that has been published to date, only under a subset of conditions is there likely to be a measurable effect of the presence of ambient odours on people's food attitudes and choices. This narrative historical review summarizes the various ways in which food odours appear to bias people's food preferences (appetite) and food choices (food consumption and purchase). Emphasis is placed on those experimental studies that have been designed to investigate how the characteristics of the olfactory stimuli (e.g., the congruency between the olfactory cues and the foods, intensity and duration of exposure to odours, and taste properties of odours) modulate the effects of olfactory cues on food behaviour. The review also explores the moderating roles of individual differences, such as dietary restraint, Body Mass Index (BMI), genetic and cultural differences in odour sensitivity and perception. Ultimately, following a review of empirical studies on food-related olfaction, current approaches in scent marketing are discussed and a research agenda is proposed to help encourage further studies on the effective application of scents in promoting healthy foods.

The pharmacological stressor yohimbine, but not U50,488, increases responding for conditioned reinforcers paired with ethanol or sucrose

RATIONALE

Environmental stimuli paired with alcohol can function as conditioned reinforcers (CRfs) and trigger relapse to alcohol-seeking. In animal models, pharmacological stressors can enhance alcohol consumption and reinstate alcohol-seeking, but it is unknown whether stress can potentiate the conditioned reinforcing properties of alcohol-paired stimuli.

OBJECTIVES

We examined whether the pharmacological stressors, the α-2 adrenoreceptor antagonist yohimbine (vehicle, 1.25, 2.5 mg/kg; IP) and the K-opioid receptor agonist U50,488 (vehicle, 1.25, 2.5 mg/kg; SC), increase responding for conditioned reinforcement, and if their effects interact with the nature of the reward (alcohol vs. sucrose). We subsequently examined the effects of yohimbine (vehicle, 1.25, 2.5 mg/kg; IP) on responding for sensory reinforcement.

METHODS

Male Long-Evans underwent Pavlovian conditioning, wherein a tone-light conditioned stimulus (CS) was repeatedly paired with 12% EtOH or 21.7% sucrose. Next, tests of responding for a CRf were conducted. Responding on the CRf lever delivered the CS, whereas responding on the other lever had no consequences. In a separate cohort of rats, the effects of yohimbine on responding just for the sensory reinforcer were examined.

RESULTS

Both doses of yohimbine, but not U50,488, increased responding for conditioned reinforcement. This enhancement occurred independently of the nature of the reward used during Pavlovian conditioning. Yohimbine-enhanced responding for a CRf was reproducible and stable over five tests; it even persisted when the CS was omitted. Both doses of yohimbine also increased responding for sensory reinforcement.

CONCLUSIONS

Yohimbine increases operant responding for a variety of sensory and conditioned reinforcers. This enhancement may be independent of its stress-like effects.

Endocrine Cephalic Phase Responses to Food Cues: A Systematic Review

Cephalic phase responses (CPRs) are conditioned anticipatory physiological responses to food cues. They occur before nutrient absorption and are hypothesized to be important for satiation and glucose homeostasis. Cephalic phase insulin responses (CPIRs) and pancreatic polypeptide responses (CPPPRs) are found consistently in animals, but human literature is inconclusive. We performed a systematic review of human studies to determine the magnitude and onset time of these CPRs. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used to develop a search strategy. The terms included in the search strategy were cephalic or hormone response or endocrine response combined with insulin and pancreatic polypeptide (PP). The following databases were searched: Scopus (Elsevier), Science Direct, PubMed, Google Scholar, and The Cochrane Library. Initially, 582 original research articles were found, 50 were included for analysis. An insulin increase (≥1μIU/mL) was observed in 41% of the treatments (total n = 119). In 22% of all treatments the increase was significant from baseline. The median (IQR) insulin increase was 2.5 (1.6-4.5) μIU/mL, 30% above baseline at 5± 3 min  after food cue onset (based on study treatments that induced ≥1 μIU/mL insulin increase). A PP increase (>10 pg/mL) was found in 48% of the treatments (total n = 42). In 21% of the treatments, the increase was significant from baseline. The median (IQR) PP increase was 99 (26-156) pg/mL, 68% above baseline at 9± 4 min  after food cue onset (based on study treatments that induced ≥1 μIU/mL insulin increase). In conclusion, CPIRs are small compared with spontaneous fluctuations. Although CPPPRs are of a larger magnitude, both show substantial variation in magnitude and onset time. We found little evidence for CPIR or CPPPR affecting functional outcomes, that is, satiation and glucose homeostasis. Therefore, CPRs do not seem to be biologically meaningful in daily life.

A stepwise approach investigating salivary responses upon multisensory food cues

Exposure to sensory food cues such as smell, vision, taste and/or texture may trigger anticipatory physiological responses such as salivation, participating on adequate metabolism of the signaled food. However, the individual contribution of each sensory modality as well as the impact of particular food products on salivation and salivary composition remains unclear. Therefore, by systematically varying sensory modalities and nutrient content of food stimuli, we investigated their effect on saliva secretion, α-amylase activity and other salivary characteristics (pH level, buffering capacity, MUC5B concentration, and total protein content). Over 3 sessions, 46 normal-weight healthy participants were exposed to 12 conditions, consisting of 4 levels of sensory stimulation (odor, odor + vision, odor + vision + taste, and odor + vision + taste + mastication) and 3 types of stimuli (bread, high-in-starch; cucumber, low-in-starch; and parafilm as non-food control) during which saliva was collected. Linear mixed models showed a significant increase in salivation with increasing levels of sensory stimulation. α-amylase secretion rate increased upon the highest level of stimulation, which involved mastication, compared to odor and odor + visual level of stimulation. Other salivary characteristics varied with the level of sensory stimulation, which might be related to the total volume of salivation. The type of stimuli did not influence the saliva composition (α-amylase concentration nor other salivary components). Our findings indicate that cumulative sensory information, rather than specific (food) product, play a vital role in anticipatory salivary responses.

Hunger and appetite during visual perception of food in eating disorders

Nineteen different slides of food items and their effects on appetite and hunger as rated on visual analogue scales were investigated in 20 bulimics and 9 anorexics (DSM-III-R) at the onset and after 8 weeks of behavioral hospital treatment; 9 controls were examined at the maximum of weight loss during a diet and at normal weight. At the onset of treatment appetite ratings were significantly lower in patients than in dieting controls. In anorexics and bulimics appetite ratings increased significantly during treatment. The sight of food did not increase reported hunger in bulimics but did so in controls. Appetite ratings, however, were significantly increased by the sight of food in bulimics as well as in controls. Despite the small sample size, it may be concluded that dieting and weight loss have different psychological implications in healthy controls and in patients with eating disorders, that dieting rather than weight per se influences appetite and that differences in hunger responsiveness to the sight of food in anorexics and bulimics seem likely.

Wearable Sensors to Characterize the Autonomic Nervous System Correlates of Food-Like Odors Perception: A Pilot Study

Background: The sense of smell has been recently recognized as one of the most important sensory features in the human being, representing a reliable biomarker for a number of clinical conditions. The relationship between olfactory function and the person’s attitude towards food has frequently been investigated, often using questionnaires. The administration of minimally invasive methods for characterizing autonomic nervous system (ANS) functionality could help in objectivizing such measurements. Methods: The present study assessed ANS activation through the analysis of the electrocardiogram (ECG) and galvanic skin response (GSR) signals, in response to olfactory stimuli using non-invasive wearable devices. The ANS activation was also studied with respect to the odor familiarity, as well as with other olfactory and food dimensions (e.g., odor identification, odor pleasantness, food neophobia). Results: We demonstrated a significant activation of the ANS, in particular of its sympathetic branch, during the olfactory stimulation, with the ECG signal seen as more sensitive to detect ANS response to moderate olfactory stimuli rather than the GSR. Conclusions: When applied to a greater number of subjects, or to specific groups of patients, this methodology could represent a promising, reliable addition to diagnostic methods currently used in clinical settings.

Do restrained eaters show increased BMI, food craving and disinhibited eating? A comparison of the Restraint Scale and the Restrained Eating scale of the Dutch Eating Behaviour Questionnaire

Despite being used interchangeably, different measures of restrained eating have been associated with different dietary behaviours. These differences have impeded replicability across the restraint literature and have made it difficult for researchers to interpret results and use the most appropriate measure for their research. Across a total sample of 1731 participants, this study compared the Restraint Scale (RS), and its subscales, to the Dutch Eating Behaviour Questionnaire (DEBQ) across several traits related to overeating. The aim was to explore potential differences between these two questionnaires so that we could help to identify the most suitable measure as a prescreening tool for eating-related interventions. Results revealed that although the two measures are highly correlated with one another (rs = 0.73-0.79), the RS was more strongly associated with external (rs = -0.07 to 0.11 versus -0.18 to -0.01) and disinhibited eating (rs = 0.46 versus 0.31), food craving (rs = 0.12-0.27 versus 0.02-0.13 and 0.22 versus -0.06) and body mass index (rs = 0.25-0.34 versus -0.13 to 0.15). The results suggest that, compared to the DEBQ, the RS is a more appropriate measure for identifying individuals who struggle the most to control their food intake.

Exacting Responses: Lack of Endocrine Cephalic Phase Responses Upon Oro-Sensory Exposure

Oro-sensory exposure (OSE) to food plays an important role in the regulation of food intake. One proposed underlying mechanism is the occurrence of cephalic phase responses (CPRs). CPRs include the pre-digestive endocrine responses induced by food-related sensory input. Yet, whether OSE duration or sweetness intensity affects CPRs is unknown. The objective of this study was to determine the independent and interactive effects of oro-sensory duration (chewing) and stimulation intensity (sweetness) on endocrine CPRs and satiation. Eighteen males (22 ± 2 years, BMI 22 ± 2 kg/m2) participated in a 2 × 2 randomized study with a control condition. Each session participants performed modified sham feeding (MSF) with one of the four gel-based model foods. During the control session no MSF was performed. Model foods differed in chewing duration (hard or soft texture) and sweetness (low or high intensity). During each session, eight blood samples were collected up till 25 min after MSF onset. Subsequently, food intake from an ad libitum lunch was measured. No typical CPR was found for insulin, pancreatic polypeptide (PP), and ghrelin. However, the overall PP response was 1.1 times greater for the hard sweet MSF condition compared to control (p = 0.02). Overall ghrelin responses were 1.1 times greater for the hard model food compared to the soft model food conditions (p = 0.003). These differences in endocrine response were not associated with differences in food intake at the subsequent meal. Exploratory sub-analysis of the responsive insulin curves showed that after 2.5 min of MSF the hard texture model foods insulin concentrations were 1.2 greater compared to the soft texture. These findings indicate that texture hardness and sweetness increase the overall PP response and that MSF on hard texture increases the overall ghrelin response compared to soft texture model foods. However, MSF on model foods does not lead to a typical CPR. This study, among others, shows that there are major dissimilarities in the endocrine responses to food stimulation between individuals. This emphasizes the importance of considering cephalic responders and non-responders. More research is needed to understand CPRs in relation to food texture and taste properties.

Consumption Simulations Induce Salivation to Food Cues

Salivation to food cues is typically explained in terms of mere stimulus-response links. However, food cues seem to especially increase salivation when food is attractive, suggesting a more complex psychological process. Adopting a grounded cognition perspective, we suggest that perceiving a food triggers simulations of consuming it, especially when attractive. These simulations then induce salivation, which effectively prepares the body for eating the food. In two experiments, we systematically examined the role of simulations on salivation to food cues. As stimuli, both experiments used an attractive, a neutral, and a sour food, as well as a non-food control object. In Experiment 1, participants were instructed to simulate eating every object they would be exposed to. We then exposed them to each object separately. Salivation was assessed by having participants spit their saliva into a cup after one minute of exposure. In Experiment 2, we instructed half of participants to simulate eating each object, and half to merely look at them, while measuring salivation as in Experiment 1. Afterwards, participants rated their simulations and desire to eat for each object separately. As predicted, foods increased salivation compared to the non-food control object, especially when they were attractive or sour (Exp. 1 and 2). Importantly, attractive and sour foods especially increased salivation when instructed to simulate (Exp. 2). These findings suggest that consumption simulations play an important role in inducing salivary responses to food cues. We discuss directions for future research as well as the role of simulations for other appetitive processes.

The role of expectations in the effect of food cue exposure on intake

Pre-exposure to food cues has often been shown to increase food intake, especially in restrained eaters. This study investigated the role of expectations in the effect of such pre-exposure on food intake. A sample of 88 undergraduate women was exposed to visual food cues (photos of grapes and chocolate-chip cookies). In a 2 × 2 × 2 design, participants were explicitly told to expect that they would be tasting and rating either grapes or chocolate-chip cookies. Participants subsequently completed an ostensible taste test, in which they tasted and rated either grapes or cookies, such that half were given the food that they had been led to expect and the other half were given the other food. Participants' restraint status (restrained versus unrestrained) was based on their scores on the Revised Restraint Scale (Herman & Polivy, 1980). A significant interaction between expected food and restraint status was found. When participants were led to expect that they would be tasting grapes, restrained and unrestrained eaters did not differ in their subsequent consumption (of either grapes or cookies). However, when participants were led to expect that they would be tasting cookies, restrained eaters ate significantly less (of both grapes and cookies) than did unrestrained eaters, even though craving ratings were similarly elevated for both restrained and unrestrained eaters. The findings are consistent with counteractive control theory in that restrained eaters who expected to eat a high caloric food may have been able to activate their dieting goal, thereby limiting their food intake. The findings further point to an important role for expectations in the understanding and regulation of food intake in restrained eaters.

Making sense of the sensory regulation of hunger neurons

AgRP and POMC neurons are two key cell types that regulate feeding in response to hormones and nutrients. Recently, it was discovered that these neurons are also rapidly modulated by the mere sight and smell of food. This rapid sensory regulation "resets" the activity of AgRP and POMC neurons before a single bite of food has been consumed. This surprising and counterintuitive discovery challenges longstanding assumptions about the function and regulation of these cells. Here we review these recent findings and discuss their implications for our understanding of feeding behavior. We propose several alternative hypotheses for how these new observations might be integrated into a revised model of the feeding circuit, and also highlight some of the key questions that remain to be answered.

A daily diary study of perceived social isolation, dietary restraint, and negative affect in binge eating

Negative affect and dietary restraint are key predictors of binge eating, yet less is known about the impact of social factors on binge eating. The study sought to replicate and extend research on the relationships between negative affect, dietary restraint, perceived social isolation and binge eating using a daily diary methodology. College women (N = 54) completed measures of dietary restraint, negative affect, perceived social isolation, and binge eating daily for 14 days. Participants completed the measures nightly each day. A series of generalized estimating equations showed that dietary restraint was associated with less binge eating while controlling for negative affect and for perceived social isolation separately. Negative affect and perceived social isolation were associated with greater binge eating while controlling for restraint in separate analyses, but only perceived social isolation was significant when modeled simultaneously. All two-way interactions between negative affect, dietary restraint, and perceived social isolation predicting binge eating were nonsignificant. This study furthers our understanding of predictors of binge eating in a nonclinical sample. Specifically, these data suggest perceived social isolation, negative affect, and dietary restraint are important variables associated with binge eating in daily life and warrant further research.

Understanding same-sex male and female partners' restrained eating in the context of their relationships

This study examined weight status and dietary restraint among same-sex couples using Actor-Partner Interdependence Models. Body mass indices and restrained eating behaviors (i.e., cognitive dietary restraint, uncontrolled eating, and emotional eating) were assessed for members of 144 same-sex couples (72 lesbian and 72 gay couples; mean age = 33.74 years, standard deviation = 11.27 years). Results indicated that both men and women who were relatively heavy and who had relatively thin partners were at particular risk of engaging in restrained eating. These findings extend our understanding of partner comparison processes within the context of same-sex relationships in determining men and women's eating behaviors.

Half full or empty: cues that lead wine drinkers to unintentionally overpour

Wine drinkers often pour their own wine, but is the amount they pour influenced by the shape of the glass, the color of the wine, or how they pour? Building on research involving visual illusions and haptic cues, an exploratory field study shows that while wine drinkers typically poured 3.95 fl. oz. of wine into a standard baseline (10 fl. oz.) glass, they poured 11.9% more into a wider glass, 9.2% more when the wine was white (the low contrast with the glass makes it difficult to see), and 12.2% more when the wine glass was held in their hand rather than sitting on the table. Using narrower wine glasses and not pouring while holding one's glass may be steps toward modestly reducing the amount of wine a social drinker pours and drinks.

A review of visual cues associated with food on food acceptance and consumption

Several sensory cues affect food intake including appearance, taste, odor, texture, temperature, and flavor. Although taste is an important factor regulating food intake, in most cases, the first sensory contact with food is through the eyes. Few studies have examined the effects of the appearance of a food portion on food acceptance and consumption. The purpose of this review is to identify the various visual factors associated with food such as proximity, visibility, color, variety, portion size, height, shape, number, volume, and the surface area and their effects on food acceptance and consumption. We suggest some ways that visual cues can be used to increase fruit and vegetable intake in children and decrease excessive food intake in adults. In addition, we discuss the need for future studies that can further establish the relationship between several unexplored visual dimensions of food (specifically shape, number, size, and surface area) and food intake.

Accepting or suppressing the desire to eat: investigating the short-term effects of acceptance-based craving regulation

Previous studies addressing the long-term impact of acceptance of food cravings have revealed positive effects in terms of reduced craving experience. The present study investigated the short-term (direct) consequences of acceptance-based craving regulation. Hungry participants were exposed to desirable food and were either instructed to accept or suppress food cravings during exposure. Control participants did not regulate cravings and were allowed to eat from the food. Participants who accepted food cravings reported a significant increase in food craving during the course of the experiment. Participants who suppressed their cravings during exposure kept their craving levels constant. In contrast, control participants who were allowed to eat from the food, reported a significant drop in cravings. These findings suggest that although acceptance may entail an effective strategy for reducing food cravings in the long run, it may require repeated practice to overcome the immediate counterproductive effects.

Acute versus repeated chocolate exposure: Effects on intake and cravings in restrained and unrestrained eaters

The cue-reactivity model, which is based on conditioning processes, posits that repeated food exposure (in the absence of consumption) should decrease cue reactivity. To examine whether repeated chocolate exposure attenuates cravings and intake, relative to those exposed to an acute cue, a 2 (repeated vs acute cue) × 2 (restrained vs unrestrained eaters) design was employed. Fifty female participants were recruited. Repeated exposure reduced cravings in unrestrained eaters (relative to acute exposure), but increased cravings in restrained eaters. An interaction between restraint and exposure emerged on intake, such that restrained eaters ate less after acute exposure than did unrestrained eaters.

Relation of dietary restraint scores to activation of reward-related brain regions in response to food intake, anticipated intake, and food pictures

Prospective studies indicate that individuals with elevated dietary restraint scores are at increased risk for future bulimic symptom onset, suggesting that these individuals may show hyper-responsivity of reward regions to food and food cues. Thus, we used functional magnetic resonance imaging (fMRI) to examine the relation of dietary restraint scores to activation of reward-related brain regions in response to receipt and anticipated receipt of chocolate milkshake and exposure to pictures of appetizing foods in 39 female adolescents (mean age=15.5 ± 0.94). Dietary restraint scores were positively correlated with activation in the right orbitofrontal cortex (OFC) and bilateral dorsolateral prefrontal cortex (DLPFC) in response to milkshake receipt. However, dietary restraint scores did not correlate with activation in response to anticipated milkshake receipt or exposure to food pictures. Results indicate that individuals who report high dietary restraint have a hyper-responsivity in reward-related brain regions when food intake is occurring, which may increase risk for overeating and binge eating.

The role of sensitivity to reward and impulsivity in food-cue reactivity

Exposure to the visual and olfactory characteristics of food can elicit a desire to eat and can stimulate food intake. This study sought to determine the extent to which sensitivity to reward and impulsivity are associated with this 'food-cue reactivity' in two motivational states (food deprived and non-food deprived). Female participants (N=120) were exposed to a pizza cue for three minutes whilst food deprived and non-food deprived. Before and after this period, three measures of food-cue reactivity were taken (ratings of desire to eat, craving, and desired portion size of the cued food). Two important findings emerged from the study. Firstly, individuals with higher levels of trait impulsivity experienced greater changes in appetite ratings in both motivational states (food deprived and non-food deprived). They also reported greater changes in desired portion size of a cued food when food deprived. Secondly, individuals with a high sensitivity to reward experienced a greater change in their desired portion of the cued food, but only when non-food deprived. These results indicate that individual differences in food-cue reactivity could be related to variation in sensitivity to stimuli that predict the occurrence of a reward, and to an inability to exercise sufficient self control in the presence of tempting environmental stimuli.

Relation of dietary restraint scores to cognitive biases and reward sensitivity

This study tested the hypotheses that dietary restraint scores are associated with greater reward sensitivity and cognitive bias for food-related cues, which might result in chronic overeating and efforts to curb this tendency through dietary restriction. Participants (N=63) with high versus low scores on the DEBQ-R did not differ on attentional bias for pictorial food-related cues on a visual probe task, or approach tendencies elicited by food cues, as assessed with a stimulus-response compatibility (SRC) task. Restraint was also unrelated to performance on an operant task that assessed how hard participants would work for snacks, or responding during a taste habituation paradigm. Dietary restraint scores were correlated with self-reported appetitive response to food, sensitivity to reward, and sensitivity to punishment. Results provide limited support for the hypothesis that individuals with elevated dietary restraint scores show greater reward sensitivity and cognitive bias for food stimuli, though it is possible that the null findings on the behavioral task resulted because of an approach-avoidance conflict to food cues in which heightened appetitive responses to food are inhibited by food-related anxiety.

Individual differences in food-cue reactivity. The role of BMI and everyday portion-size selections

This study sought to explore the association between sensitivity to food cues (sight and smell of food) and (i) body weight (overweight or non-overweight), (ii) typical everyday portion sizes, and (iii) the DEBQ-restraint scale. One hundred and twenty female participants (aged between 18 and 30) were exposed to the sight and smell of pizza for three minutes. Both before and after this period, three measures of food-cue reactivity were taken (ratings of desire to eat, craving, and a measure of desired portion size of the cued food). Separate regression analyses were used to explore the associations between the change in measures of cue reactivity from pre- to post-cue exposure, and (i) an overweight/non-overweight classification, (ii) a measure of participants everyday portion-size selection, and (iii) scores on the DEBQ-restraint scale. This analysis revealed that scores on the DEBQ-restraint scale were not significantly associated with changes in food-cue reactivity. However, individuals identified as overweight, and participants who reported consuming the largest everyday portion sizes, experienced a significantly greater change in their desired portion size of the cued food. The findings suggest that heightened food-cue reactivity might present an under-explored risk factor for overeating, and becoming overweight, and/or maintaining an overweight body shape.

How emotions affect eating: a five-way model

Despite the importance of affective processes in eating behaviour, it remains difficult to predict how emotions affect eating. Emphasizing individual differences, previous research did not pay full attention to the twofold variability of emotion-induced changes of eating (variability across both individuals and emotions). By contrast, the present paper takes into account both individual characteristics and emotion features, and specifies five classes of emotion-induced changes of eating: (1) emotional control of food choice, (2) emotional suppression of food intake, (3) impairment of cognitive eating controls, (4) eating to regulate emotions, and (5) emotion-congruent modulation of eating. These classes are distinguished by antecedent conditions, eating responses and mediating mechanisms. They point to basic functional principles underlying the relations between emotions and biologically based motives: interference, concomitance and regulation. Thus, emotion-induced changes of eating can be a result of interference of eating by emotions, a by-product of emotions, and a consequence of regulatory processes (i.e., emotions may regulate eating, and eating may regulate emotions).

How visual images of chocolate affect the craving and guilt of female dieters

This study asks whether exposure to images of chocolate induces cravings and guilty feelings in females. A further aim was to examine whether these effects are heightened in the case of dieters. The participants, 85 females, saw a series of enticing media images, either of chocolate or of non-food products. Two thirds of the sample were dieting or had dieted in the past; 15% had been on seven or more diets. After viewing the images all participants completed the Attitudes to Chocolate Questionnaire (ACQ) [Benton, Greenfield, & Morgan (1998). The development of the attitudes to chocolate questionnaire. Personality and Individual Differences, 24(4), 513-520]. The different conditions affected only those who dieted. Dieters had significantly higher ACQ scores after viewing the chocolate images than the non-dieters. It is suggested that dietary restriction increases desire for forbidden foods, in the form of craving, and may induce negative affect such as guilt, anxiety and depression.

The environment influences whether high-fat foods are associated with palatable or with unhealthy

This study investigated whether relatively automatic evaluations of food differ between situations and between obese people and lean controls. These evaluations were assessed in the affective priming paradigm (APP) -- a response latency based measure for associations. In Experiment 1, we either focused participants (33 obese and 26 lean controls) on the palatability (restaurant condition) or on the healthiness (health condition) of food, prior to the APP. Independent of weight-status, relatively automatic evaluations of food were based on palatability in the restaurant condition, and on health in the health condition. So, the current focus of attention can shape the way foods are evaluated relatively automatically. In Experiment 2, craving was induced in participants (27 obese and 29 lean controls). Unexpectedly, the craving induction did not achieve its goal of focusing on the palatability of food in general, but just for low-fat foods, possibly because of the health-emphasizing environment -- a hospital. Interestingly, obese people showed a stronger palatability priming effect with increasing levels of initial craving. For normal weight controls the effect was in the same direction, but missed significance. In our environment, palatability of food may be too salient, and health may not be salient enough, influencing automatic food-evaluations.

Stress-induced eating in restrained eaters may not be caused by stress or restraint

Restrained eaters tend to increase and unrestrained eaters to decrease their food intake when stressed. This relationship, though robust, does not appear to be caused by restrained eating or by stress per se. For restraint, evidence indicates that none of the common operationalizations of restraint can account for restraint-related effects that have been examined to date. It is therefore unlikely that restraint is responsible for stress-induced eating in restrained eaters. Rather, behavioral and physiological data suggest that restrained eating may be a proxy risk factor for vulnerability to weight gain. For stress, a variety of minimally stressful perturbations (e.g. non-threatening cognitive loads) have been shown to elicit increased intake in restrained eaters. Thus, the negative affect created by manipulations used to create stress (e.g. scary movies, failure at a task) does not appear to be necessary to provoke overeating. An adequate explanation for stress-induced eating in restrained eaters remains elusive.

Potential early-life predictors of dietary behaviour in adulthood: a retrospective study

OBJECTIVE

Unnecessary dietary restraint (ie in the absence of a need to lose weight) and chronic overeating are both very unhealthy activities. As a precursor to a more involved longitudinal study, we sought to identify potential early-life predictors that merit scrutiny in this context.

DESIGN

Four retrospective questionnaire studies were conducted (Study 1, N=242; Study 2, N=297; Study 3, N=175; Study 4, N=261). Female participants (18-30 y) completed measures of current dietary restraint and overeating. They also recalled experiences between 5 and 10 years of age. All were staff or students at Loughborough University (UK).

RESULTS

After considering obvious sources of systematic bias, we report evidence that (i) dietary restraint is related to memories of maternal weight and dietary behaviour, and (ii) overeating and meal-size selection are both associated with memories of receiving a high-energy diet.

CONCLUSION

The role of maternal factors in dietary restraint is consistent with previous research exploring the early onset of this behaviour. However, the relationship between childhood diet and overeating has not been suggested elsewhere. This is particularly important because it suggests a previously unreported correspondence between childhood experience and behaviours associated with obesity in adulthood.

At first sight: how do restrained eaters evaluate high-fat palatable foods?

Two experiments tested the hypothesis that restrained eaters display a greater liking for high-fat palatable foods, than do unrestrained eaters. This hypothesis was tested in the affective priming paradigm and in the extrinsic affective Simon task . Both paradigms were successful in uncovering food likes and dislikes, and both showed that participants were able to evaluate the palatability of foods relatively automatically. However, contrary to the hypothesis, food likes were not substantially affected by fat content, nor were they affected by restraint-status. Restrained and unrestrained eaters may like high-fat palatable foods to the same extent, but may differ in their craving for these foods.

Effect of ambience on food intake and food choice

Eating takes place in a context of environmental stimuli known as ambience. Various external factors such as social and physical surroundings, including the presence of other people and sound, temperature, smell, color, time, and distraction affect food intake and food choice. Food variables such as the temperature, smell, and color of the food also influence food intake and choice differently. However, the influence of ambience on nutritional health is not fully understood. This review summarizes the research on ambient influences on food intake and food choice. The literature suggests that there are major influences of ambience on eating behavior and that the magnitude of the effect of ambience may be underestimated. Changes in intake can be detected with different levels of the number of people present, food accessibility, eating locations, food color, ambient temperatures and lighting, and temperature of foods, smell of food, time of consumption, and ambient sounds. It is suggested that the manipulation of these ambient factors as a whole or individually may be used therapeutically to alter food intake and that more attention needs to be paid to ambience in nutrition-related research.

ENVIRONMENTAL FACTORS THAT INCREASE THE FOOD INTAKE AND CONSUMPTION VOLUME OF UNKNOWING CONSUMERS

Package size, plate shape, lighting, socializing, and variety are only a few of the environmental factors that can influence the consumption volume of food far more than most people realize. Although such environmental factors appear unrelated, they generally influence consumption volume by inhibiting consumption monitoring and by suggesting alternative consumption norms. For researchers, this review suggests that redirecting the focus of investigations to the psychological mechanisms behind consumption will raise the profile and impact of research. For health professionals, this review underscores how small structural changes in personal environments can reduce the unknowing overconsumption of food.

Dietary restraint and heightened reactivity to food

Previously, studies have explored the relationship between dietary behavior and salivary reactivity to food. Despite this, it remains unclear which behaviors are associated with enhanced reactivity. One problem is that measures of behavior have not been compared directly. In particular, it is unclear whether elevated reactivity is associated with measures of dietary restraint or with measures of failed dietary control and a tendency to overeat. To address this problem, we compared the association between salivary reactivity and scores on the subscales of the Three-Factor Eating Questionnaire (restraint, disinhibition, and hunger). Estimates of reactivity were derived from the difference between a baseline saliva measure and a similar measure taken in close proximity to hot pizza. Our second aim was to explore how salivary reactivity changes after a meal. Female participants (N=40) were tested before and after a lunch (cheese sandwiches). All tended to show reactivity to pizza before but not after lunch. No significant differences were associated with the disinhibition or hunger subscales. However, prelunch reactivity was significantly greater in those participants with high scores on the restraint scale. This does not appear to be related to reported levels of hunger before lunch. Rather, it may reveal an intrinsic difference between the reaction of restrained and unrestrained eaters to food.

Anticipatory effects of food exposure in women diagnosed with bulimia nervosa

OBJECTIVE

To investigate cephalic phase responses (CPRs) in women diagnosed with bulimia nervosa and to test the assumption that eating disordered individuals respond with more marked CPRs and higher increases in psychophysiological arousal to the presentation of food cues.

METHOD

Thirteen female inpatients diagnosed with bulimia nervosa were compared to 15 non-eating disordered female volunteers. Participants were exposed to their preferred binge food in a single laboratory session with the possibility to eat immediately after the exposure trial.

RESULTS

The results show greater salivation responses to food exposure and lower sympathetic arousal in patients diagnosed with bulimia nervosa than in non-eating-disordered participants. Distress and feelings of tension and insecurity during food exposure were higher in patients compared to controls.

DISCUSSION

These results support the hypothesis that anticipatory cephalic phase responses are more marked in eating disordered individuals and may therefore play a role in the maintenance of binge eating behavior.

The specificity of restrained versus unrestrained eaters' responses to food cues: general desire to eat, or craving for the cued food?

Previous research has shown that exposure to food cues increases eating, especially in restrained eaters. The present study attempted to determine whether this elevated consumption reflects a general desire to eat in response to food cues, or specific desire/craving for the cued food. Restrained and unrestrained eaters were exposed to the smell of either pizza, cookies, or no smell for 10 minutes, were asked to write their thoughts (corresponding to the smell cue) about pizza, cookies or in general, and were then presented with either pizza or cookies to 'taste and rate'. Results indicated that restrained eaters are more responsive than are unrestrained eaters to pre-eating exposure to smell and thought cues, eating significantly more after such cues. An interaction with food type, however, indicated that restrained eaters ate more only when the food presented to eat was the same as the prior food cues. Self-reported desire to eat, liking, and craving for a particular food increased somewhat for restrained eaters after exposure to the smell and thought of that food. Restrained eaters' intake of a food that differed from the pre-eating food cues did not differ from their intake following no prior exposure to food cues. Restrained eaters thus showed a highly specific response to exposure to food cues.

Cephalic phase responses, craving and food intake in normal subjects

Cephalic phase responses (CPRs) are elicited during exposure to food cues. They gear up the body to optimize digestion or they compensate for unwanted changes during a meal. The cue reactivity model of binge eating predicts that CPRs are experienced as craving for food, thereby increasing food intake and playing a role in abnormal eating behaviour. The present experiment was designed to measure CPRs in normal women and to examine its relationship with craving, food intake and restraint. Results show that normal subjects do react to food exposure with changes in heart rate, heart rate variability (HRV), salivation, blood pressure, skin conductance and gastric activity. These CPRs presumably gear up the body and presumably do not reflect compensatory responses. Significant correlations between restraint and blood pressure, between blood pressure and craving, and between craving and food intake were also found. These results are in line with the cue reactivity model and suggest that research into physiological CPRs and craving in the field of eating disorders is valuable.

Nutritional implications of the cephalic-phase salivary response

The rapid release of saliva following cognitive or sensory stimulation is termed the cephalic phase salivary response. Optimal methods and conditions for measuring the cephalic phase salivary response have not been established. Consequently, determination of the extent to which the large inter and intra-individual variability reflect biological or procedural influences is not possible. The nutritional significance of the response may be great due to the multiple roles played by saliva in food selection and digestion. The cephalic phase salivary response has been proposed as an objective index of various individual states (e.g. hunger) and characteristics (e.g. dietary restraint, extroversion), but its value for such purposes requires further verification.

Recording of swallowing events using electromyography as a non-invasive measurement of salivation

The present study examined whether the measurement of swallowing activity by electromyography (EMG) provides a sensitive and valid method for the assessment of the amount of saliva secreted. Thirteen subjects tasted lemon juice and water, and smelled lasagna and hay, while the amount of saliva, measured with the aid of cotton dental rolls, was compared with the number of peaks in the EMG activity of the musculus digastricus. Swallowing indeed differentiated between the stimuli and the correlation between the number of swallows and the amount of saliva was significant. The present data suggest that monitoring the swallowing movement using EMG might be a sensitive, valid and reliable method for the measurement of salivary flow. The use is recommended for the measurement of salivation when a simple and non-invasive method is needed.