Vegetarianism and food perception. Selective visual attention to meat pictures

Altered Brain Reactivity to Food Cues in Undergraduate Students with Disordered Eating Behaviors

PURPOSE

A growing body of evidence has shown that electroencephalography (EEG) is an interesting method of assessing the underlying brain physiology associated with disordered eating. Using EEG, we sought to evaluate brain reactivity to hyper-palatable food cues in undergraduate students with disordered eating behavior (DEB).

METHODS

After assessing the eating behaviors of twenty-six undergraduate students using the Eating Attitudes Test (EAT-26), electroencephalographic signals were recorded while the participants were presented with pictures of hyper-palatable food. The current study used a temporospatial principal component analysis (PCA) approach to identify event-related potential (ERP) responses that differed between DEB and non-DEB individuals.

RESULTS

A temporospatial PCA applied to the ERPs identified a positivity with a maximum amplitude at 347 ms at the occipital-temporal electrodes in response to pictures of hyper-palatable food. This positivity was correlated with the EAT-26 scores. Participants with DEB showed reduced positivities in this component compared with those without DEB.

CONCLUSION

Our findings may reflect greater motivated attention toward hyper-palatable food cues in undergraduate students with DEB. These results are an important step toward obtaining a more refined understanding of specific abnormalities related to reactivity to food cues in this population.

Diet and odor hedonic ratings: comparative study between vegetarians, flexitarians, and omnivores

OBJECTIVES

Odor hedonic perception is well known to exhibit great variability and to depend on several parameters, i.e. stimulus, context, and subject characteristics. As hedonic perception (pleasant/unpleasant character) of food odors is considered one of the most prominent dimensions in eating behavior, the question of hedonic variability in this context arises. Thus, the aim of the present study was to compare odor hedonic ratings in three populations with regard to diet (i.e. omnivore, vegetarian, and flexitarian diets).

METHODS

Four categories of odors were compared: meat, vegetable, other food, and non-food odors.

RESULTS

The results showed that vegetarian and flexitarian individuals rated meat odors as more unpleasant than omnivores, while no significant difference was found for other categories of odors.

DISCUSSION

The question of whether the diet influences the hedonic perception or/and inversely is discussed, regarding several aspects of food consumption such as eating disorders, food education, … and could further serve to manage eating behaviors.

PRACTICAL APPLICATIONS

This study evidenced that vegetarians and flexitarians specifically rated meat odors as being more unpleasant than those of omnivores. Because of the growing number of vegetarians and flexitarians in the general population, it could be suggested to take into account the odor hedonic perception (especially regarding food odors) in studies related to diets. Besides, the present results could further serve research in several aspects of food consumption such as eating disorders (anorexia, bulimia … etc.) or food education as well as the management of eating behaviors, especially in an elderly population.

The Application of Biometric Approaches in Agri-Food Marketing: A Systematic Literature Review

A challenge in social marketing studies is the cognitive biases in consumers' conscious and self-reported responses. To help address this concern, biometric techniques have been developed to obtain data from consumers' implicit and non-verbal responses. A systematic literature review was conducted to explore biometric applications' role in agri-food marketing to provide an integrated overview of this topic. A total of 55 original research articles and four review articles were identified, classified, and reviewed. It was found that there is a steady growth in the number of studies applying biometric approaches, with eye-tracking being the dominant method used to investigate consumers' perceptions in the last decade. Most of the studies reviewed were conducted in Europe or the USA. Other biometric techniques used included facial expressions, heart rate, body temperature, and skin conductance. A wide range of scenarios concerning consumers' purchase and consumption behaviour for agri-food products have been investigated using biometric-based techniques, indicating their broad applicability. Our findings suggest that biometric techniques are expanding for researchers in agri-food marketing, benefiting both academia and industry.

Reversing food preference through multisensory exposure

Experiencing food craving is nearly ubiquitous and has several negative pathological impacts prompting an increase in recent craving-related research. Food cue-reactivity tasks are often used to study craving, but most paradigms ignore the individual food preferences of participants, which could confound the findings. We explored the neuropsychological correlates of food craving preference using psychophysical tasks on human participants considering their individual food preferences in a multisensory food exposure set-up. Participants were grouped into Liked Food Exposure (LFE), Disliked Food Exposure (DFE), and Neutral Control (NEC) based on their preference for sweet and savory items. Participants reported their momentary craving for the displayed food stimuli through the desire scale and bidding scale (willingness to pay) pre and post multisensory exposure. Participants were exposed to food items they either liked or disliked. Our results asserted the effect of the multisensory food exposure showing a statistically significant increase in food craving for DFE participants postexposure to disliked food items. Using computational models and statistical methods, we also show that the desire for food does not necessarily translate to a willingness to pay every time, and instantaneous subjective valuation of food craving is an important parameter for subsequent action. Our results further demonstrate the role of parietal N200 and centro-parietal P300 in reversing food preference and possibly point to the decrease of inhibitory control in up-regulating craving for disliked food.

Forty-five years of research on vegetarianism and veganism: A systematic and comprehensive literature review of quantitative studies

Meat production and consumption are sources of animal cruelty, responsible for several environmental problems and human health diseases, and contribute to social inequality. Vegetarianism and veganism (VEG) are two alternatives that align with calls for a transition to more ethical, sustainable, and healthier lifestyles. Following the PRISMA guidelines, we conducted a systematic literature review of 307 quantitative studies on VEG (from 1978 to 2023), collected from the Web of Science in the categories of psychology, behavioral science, social science, and consumer behavior. For a holistic view of the literature and to capture its multiple angles, we articulated our objectives by responding to the variables of "WHEN," "WHERE," "WHO," "WHAT," "WHY," "WHICH," and "HOW" (6W1H) regarding the VEG research. Our review highlighted that quantitative research on VEG has experienced exponential growth with an unbalanced geographical focus, accompanied by an increasing richness but also great complexity in the understating of the VEG phenomenon. The systematic literature review found different approaches from which the authors studied VEG while identifying methodological limitations. Additionally, our research provided a systematic view of factors studied on VEG and the variables associated with VEG-related behavior change. Accordingly, this study contributes to the literature in the field of VEG by mapping the most recent trends and gaps in research, clarifying existing findings, and suggesting directions for future research.

Impact of textual warnings on emotional brain responses to ultra-processed food products

Background and objectives

Ultra-processed food products (UPF) have been associated with numerous non-communicable diseases. Despite this, the addictive nature of UPF, and the aggressive marketing strategies used to promote them, has created a strong emotional connection between UPF and consumers, and supports their increasing UPF global consumption. In view of the emotional link that consumers often have with UPF, modulating emotional reactions to UPF (by using strategies such as textual warnings) is important in changing consumers' behavior. Since emotions are better understood by assessing individuals' implicit reactions, we conducted an electroencephalographic study applying the event-related potential technique to investigate whether textual warnings were able to modulate the brain responses to UPF stimuli.

Materials and methods

Twenty-six participants (19 women) viewed pictures of UPF preceded by a warning sentence about the health risks of consuming UPF or a control sentence while the electroencephalogram was recorded. In addition, the participants rated the picture in respect of pleasantness, arousal, and intention to consume. As emotions are associated with motivational circuits in the brain, we focused on a well-known event-related potential brain marker of the motivational relevance associated with emotional stimuli, namely late positive potential (LPP).

Results

The late positive potential amplitude was larger for pictures depicting UPF under the warning condition compared to the control condition, a result that was accompanied by lower pleasantness ratings during the warning condition (compared to the control).

Conclusion

Textual warnings about the negative health consequences of consuming UPF changed the emotional responses toward UPF, possibly increasing the motivation to avoid UPF. These results shed new light on the impact of textual warnings on UPF-evoked emotions.

Public concern for animal welfare and its correlation with ethical ideologies after coronavirus disease (COVID-19) in China

The outbreak of coronavirus disease (COVID-19) represents a major public health challenge and a serious threat to sustainable social development. A consideration of animal welfare is clearly justified, given the potential contribution of animals to the spread of the disease. The present study, therefore, sought to investigate the concern the Chinese people have for animal welfare (PCAW) and how their 'ethical ideology' (idealism and relativism) determines PCAW after COVID-19, through comparison with the same study, carried out in China in 2015. Our results demonstrated a significant improvement in Chinese PCAW after COVID-19. The adverse impact of COVID-19 may have resulted in a lowered idealism score and this decreased score served to neutralise significant correlations between idealism and PCAW, compared to the 2015 results. The global pandemic did not increase people's relativism score and a significant correlation was found between relativism and PCAW. Gender, age, educational level, public perception of animals after COVID-19, zoo and aquarium visiting were all shown to be predictor variables for PCAW. This study is one of the first to investigate Chinese PCAW after COVID-19 and can therefore provide knowledge that will potentially increase Chinese PCAW.

Using event-related potentials to study food-related cognition: An overview of methods and perspectives for future research

Electroencephalography (EEG), and the measure of event-related potentials (ERPs) in particular, are useful methods to study the cognitive and cerebral mechanisms underlying the perception and processing of food cues. Further research on these aspects is necessary to better understand how cognitive functioning may influence food choices in different populations (e.g. obese individuals, individuals with eating disorders). To help researchers in designing future studies, this article provides an overview of the methods used in the current literature on ERPs and food-related cognition. Several methodological aspects are explored to outline interesting perspectives for future research, including discussions on the main experimental tasks used, the cognitive functions assessed (e.g. inhibitory control, attentional processing), the characteristics of the participants recruited (e.g. weight status, eating behaviors), and the stimuli selected (e.g. food pictures, odors). The issues generated by some of these methodological choices are discussed, and a few guidelines are provided.

Visual food cue processing in children with Prader-Willi Syndrome

Hyperphagia and the associated interest in food is a characteristic feature of Prader-Willi syndrome (PWS) that emerges during childhood and remains a life-long concern. This study examined neural responses reflecting food cue salience in children with PWS and typical controls, age 3-12 years. Visual event-related potentials were recorded while participants in satiated state passively viewed photographs of high- and low-calorie foods, animals, and neutral objects. Contrary to the prediction, children with PWS did not demonstrate greater than typical neural responses to food, suggesting that it is not an exceptionally motivationally salient stimulus in PWS. Caregiver reports of greater hyperphagia were associated with neural responses to low-calorie foods suggesting accelerated and more fine-grained visual stimulus categorization in terms of edibility and caloric content. Overall, the findings align more closely with the altered satiety rather than increased food reward models of hyperphagia in PWS.

Food-Cal: development of a controlled database of high and low calorie food matched with non-food pictures

BACKGROUND

Industrialization has led to more varied and attractive high-calorie foods. Health problems such as obesity and diabetes are partially attributed to eating-related self-regulation difficulties that may be caused by increasingly frequent cues for highly palatable foods. Research studies aim at understanding the factors underlying responses to food cues. This has led to the development of food stimuli databases. However, they present some limitations.

OBJECTIVES

This study aimed at providing a controlled set of pictures, including 40 food pictures with high- and low-calorie stimuli, matched with 40 non-food pictures. The second objective was to provide a ready-to-use database with normative data regarding responses and associations between demographic, anthropometric and eating-related characteristics, and picture ratings.

PARTICIPANTS

A sample of 264 participants rated the total set of pictures.

MEASURES

Attractiveness, arousal and palatability were assessed for each picture, as well as participant's current type of diet, BMI, hunger levels and eating behaviors (uncontrolled and emotional eating).

RESULTS

Image characteristics (shape, colors, luminance) were comparable between food and matched non-food pictures. Positive correlations were found between hunger levels and attractiveness, arousal and palatability of food. Uncontrolled and emotional eating was positively correlated with high-calorie food palatability, and uncontrolled eating was positively correlated with high-calorie food attractiveness. Participants who did not report any specific diet rated high-calorie foods as more attractive and arousing, whereas vegan and vegetarian participants assessed low-calorie foods as more attractive and palatable.

CONCLUSION

The Food-Cal controlled set of picture database can be considered as a useful tool for experimental research.

LEVEL OF EVIDENCE

Level V, cross-sectional descriptive study.

CROCUFID: A Cross-Cultural Food Image Database for Research on Food Elicited Affective Responses

We present CROCUFID: a CROss-CUltural Food Image Database that currently contains 840 images, including 479 food images with detailed metadata and 165 images of non-food items. The database includes images of sweet, savory, natural, and processed food from Western and Asian cuisines. To create sufficient variability in valence and arousal we included images of food with different degrees of appetitiveness (fresh, unfamiliar, molded or rotten, spoiled, and partly consumed). We used a standardized photographing protocol, resulting in high resolution images depicting all food items on a standard background (a white plate), seen from a fixed viewing (45°) angle. CROCUFID is freely available under the CC-By Attribution 4.0 International license and hosted on the OSF repository. The advantages of the CROCUFID database over other databases are its (1) free availability, (2) full coverage of the valence - arousal space, (3) use of standardized recording methods, (4) inclusion of multiple cuisines and unfamiliar foods, (5) availability of normative and demographic data, (6) high image quality and (7) capability to support future (e.g., virtual and augmented reality) applications. Individuals from the United Kingdom (N = 266), North-America (N = 275), and Japan (N = 264) provided normative ratings of valence, arousal, perceived healthiness, and desire-to-eat using visual analog scales (VAS). In addition, for each image we computed 17 characteristics that are known to influence affective observer responses (e.g., texture, regularity, complexity, and colorfulness). Significant differences between groups and significant correlations between image characteristics and normative ratings were in accordance with previous research, indicating the validity of CROCUFID. We expect that CROCUFID will facilitate comparability across studies and advance experimental research on the determinants of food-elicited emotions. We plan to extend CROCUFID in the future with images of food from a wide range of different cuisines and with non-food images (for applications in for instance neuro-physiological studies). We invite researchers from all parts of the world to contribute to this effort by creating similar image sets that can be linked to this collection, so that CROCUFID will grow into a truly multicultural food database.

Vegetarians' and omnivores' affective and physiological responses to images of food

Many vegetarians report that meat is unpleasant, but little else is known about their affective responses to meat and non-meat foods. Here we explored affective responses to food images in vegetarians and omnivores and tested the hypothesis that vegetarians have global differences in affective processing (e.g., increased disgust sensitivity). We presented pictures of different food items and recorded participants' affective experience while we recorded peripheral physiology. We found that vegetarians' self-reported experience of meat meal images was less pleasant than omnivores', but that other food images were equally pleasant across the two groups. Moreover, vegetarians and omnivores had strikingly similar physiological responses to all food images - including meat meals. We interpret these results from a psychological constructionist perspective, which posits that individuals conceptualize changes in their bodily states in ways that match their beliefs, such that increased sympathetic nervous system activity may be conceptualized as an experience of excitement about a delicious meat meal for omnivores but as an experience of displeasure for a vegetarian who believes meat is cruel, wasteful, impure, or unhealthy. This interpretation is consistent with emerging neuroscience evidence that the brain constructs experience by predicting and making meaning of internal sensations based on past experience and knowledge.

Of Meat and Men: Sex Differences in Implicit and Explicit Attitudes Toward Meat

Modern attitudes to meat in both men and women reflect a strong meat-masculinity association. Sex differences in the relationship between meat and masculinity have not been previously explored. In the current study we used two IATs (implicit association tasks), a visual search task, and a questionnaire to measure implicit and explicit attitudes toward meat in men and women. Men exhibited stronger implicit associations between meat and healthiness than did women, but both sexes associated meat more strongly with 'healthy' than 'unhealthy' concepts. As 'healthy' was operationalized in the current study using terms such as "virile" and "powerful," this suggests that a meat-strength/power association may mediate the meat-masculinity link readily observed across western cultures. The sex difference was not related to explicit attitudes to meat, nor was it attributable to a variety of other factors, such as a generally more positive disposition toward meat in men than women. Men also exhibited an attention bias toward meats, compared to non-meat foods, while females exhibited more caution when searching for non-meat foods, compared to meat. These biases were not related to implicit attitudes, but did tend to increase with increasing hunger levels. Potential ultimate explanations for these differences, including sex differences in bio-physiological needs and receptivity to social signals are discussed.

Emotional eating and instructed food-cue processing in adolescents: An ERP study

We examined the P3 (250-500ms) and Late Positive Potential (LPP; 500-2000ms) event-related potentials (ERPs) to food vs. nonfood cues among adolescents reporting on emotional eating (EE) behavior. Eighty-six adolescents 10-17 years old were tested using an instructed food versus nonfood cue viewing task (imagine food taste) during high-density EEG recording. Self-report data showed that EE increased with age in girls, but not in boys. Both P3 and LPP amplitudes were greater for food vs. nonfood cues (food-cue bias). Exploratory analyses revealed that, during the LPP time period, greater EE was associated with a more positive food-cue bias in the fronto-central region. This heightened fronto-central food-cue bias LPP is in line with a more activated prefrontal attention system. The results suggest that adolescents with higher EE may engage more top-down cognitive resources to regulate their automatic emotional response to food cues, and/or they may exhibit greater reward network activation to food cues than do adolescents with lower EE, even in the absence of an emotional mood induction.

Processing of visual food cues during bitter taste perception in female patients with binge-eating symptoms: A cross-modal ERP study

OBJECTIVE

In healthy individuals, the perception of an intense bitter taste decreased the reward value of visual food cues, as reflected by the reduction of a specific event-related brain potential (ERP), frontal late positivity. The current cross-modal ERP study investigated responses of female patients with binge-eating symptoms (BES) to this type of visual-gustatory stimulation.

METHODS

Women with BES (n=36) and female control participants (n=38) viewed food images after they rinsed their mouth with either bitter wormwood tea or water.

RESULTS

Relative to controls, the patients showed elevated late positivity (LPP: 400-700ms) to the food images in the bitter condition. The LPP source was located in the medial prefrontal cortex. Both groups did not differ in the ratings for the fluids (intensity, bitterness, disgust).

CONCLUSIONS

This ERP study showed that a bitter taste did not decrease late positivity to visual food cues (reflecting food reward) in women with BES.

SIGNIFICANCE

The atypical bitter responding might be a biological marker of this condition and possibly contributes to overeating. Future studies should additionally record food intake behavior to further investigate this mechanism.

Neural Correlates of the Perception of Spoiled Food Stimuli

The elicitation of disgust by the view of spoiled and rotten foods is considered as an adaptation preventing the ingestion of harmful microorganisms and pathogens. To provide an effective behavioral defense, inedible food items need to be detected automatically, i.e., in the absence of explicit processing goals, early in the processing stream, and triggering an alarm response, i.e., increased attentional capture. To examine these hypotheses, a set of stimulus material consisting of images of perishable foods (i.e., dairies, meats, fruits, and vegetables) at various stages of natural decay ranging from appetitive to disgusting was developed. In separate sessions, functional imaging and dense sensor event related potential (ERP) data were collected while participants (N = 24) viewed the stimulus materials. Functional imaging data indicated larger activations in the extrastriate visual cortex during the processing of inedible as compared to edible food items. Furthermore, ERP recordings indicated that the processing of inedible food stimuli was associated with a relative positivity over inferior occipital sensor sites already at early stages of processing (<200 ms), and subsequently, an increased late positive potential (LPP) over parieto-occipital sensor regions. Taken together, these findings demonstrate the brain's sensitivity to visual cues of foods that are spoiled or rotten.

Food-pics: an image database for experimental research on eating and appetite

Our current environment is characterized by the omnipresence of food cues. The sight and smell of real foods, but also graphically depictions of appetizing foods, can guide our eating behavior, for example, by eliciting food craving and influencing food choice. The relevance of visual food cues on human information processing has been demonstrated by a growing body of studies employing food images across the disciplines of psychology, medicine, and neuroscience. However, currently used food image sets vary considerably across laboratories and image characteristics (contrast, brightness, etc.) and food composition (calories, macronutrients, etc.) are often unspecified. These factors might have contributed to some of the inconsistencies of this research. To remedy this, we developed food-pics, a picture database comprising 568 food images and 315 non-food images along with detailed meta-data. A total of N = 1988 individuals with large variance in age and weight from German speaking countries and North America provided normative ratings of valence, arousal, palatability, desire to eat, recognizability and visual complexity. Furthermore, data on macronutrients (g), energy density (kcal), and physical image characteristics (color composition, contrast, brightness, size, complexity) are provided. The food-pics image database is freely available under the creative commons license with the hope that the set will facilitate standardization and comparability across studies and advance experimental research on the determinants of eating behavior.

Time course of electrocortical food-cue responses during cognitive regulation of craving

In our current obesogenic environment, exposure to visual food-cues can easily lead to craving and overeating because short-term, pleasurable effects of food intake dominate over the anticipated long-term adverse effects such as weight gain and associated health problems. Here we contrasted these two conditions during food-cue presentation while acquiring event-related potentials (ERPs) and subjective craving ratings. Female participants (n = 25) were presented with either high-calorie (HC) or low-calorie (LC) food images under instructions to imagine either immediate (NOW) or long-term effects (LATER) of consumption. On subjective ratings for HC foods, the LATER perspective reduced cravings as compared to the NOW perspective. For LC foods, by contrast, craving increased under the LATER perspective. Early ERPs (occipital N1, 150-200 ms) were sensitive to food type but not to perspective. Late ERPs (late positive potential, LPP, 350-550 ms) were larger in the HC-LATER condition than in all other conditions, possibly indicating that a cognitive focus on negative long-term consequences induced negative arousal. This enhancement for HC-LATER attenuated to the level of the LC conditions during the later slow wave (550-3000 ms), but amplitude in the HC-NOW condition was larger than in all other conditions, possibly due to a delayed appetitive response. Across all conditions, LPP amplitudes were positively correlated with self-reported emotional eating. In sum, results reveal that regulation effects are secondary to an early attentional analysis of food type and dynamically evolve over time. Adopting a long-term perspective on eating might promote a healthier food choice across a range of food types.

The implicit nature of the anti-fat bias

The stigmatization and discrimination of obese persons is pervasive in almost any domain of living. At the explicit level, obese people are associated with a wide range of negative characteristics. Furthermore, research with the implicit association test revealed the implicit nature of the anti-fat bias. Building upon these findings, the present study used event-related brain potential recordings in order to assess key features of implicit processes. Participants viewed a series of schematic portrayals of anorexic, medium, and obese body shapes and tools. In a passive viewing condition, participants were asked to simply look at the stimuli and, in a distraction condition, participants were asked to detect a specific tool. Viewing obese body images, as compared to medium or anorexic body images, elicited a positive potential shift over fronto-central sites and a relative negative potential over occipito-temporal regions in a time window from ∼190 to 250 ms. This evaluative brain response to obese body images was similarly pronounced while participants performed a distraction task. Thus, the findings suggest that the anti-fat bias may occur spontaneously, unintentionally, and independent of explicit processing goals. A troublesome picture is emerging in Western cultures suggesting that obese-ism may appear to be as inevitable as a reflex.