The Presence of Real Food Usurps Hypothetical Health Value Judgment in Overweight People

Perceived food value depends on display format, preference strength, and physical accessibility

In everyday life, dietary decisions are made in response to real foods, such as at the grocery store or cafe. In stark contrast, decision-making studies in the laboratory typically measure responses to food stimuli presented as two-dimensional pictures or computer images, with the assumption that artificial displays are adequate substitutes for their real-world counterparts. Yet accumulating evidence challenges this view, including studies showing that willingness-to-pay (WTP) is higher for foods displayed as real objects versus images -a phenomenon known as the "real object advantage" in valuation. Here, we examined whether the "real object advantage" is modulated by accessibility to the stimuli, subjective food preference, or interactions between these factors. Participants placed monetary bids on snack foods displayed as real objects or computer images. Critically, on half of the trials, a transparent barrier was positioned between the participant and the stimulus. Linear mixed-effects modeling analysis revealed that, overall, WTP was ∼7 % higher for foods displayed as real objects versus images; however, this effect emerged only for foods of moderate (but not strong) preference strength. WTP was also higher when the stimuli appeared unoccluded versus behind the barrier, but this was equally so for real objects and images, suggesting that the barrier's effect on valuation was not related to stimulus actability. Our findings suggest that while eliminating perceived barriers to a good can bolster valuation regardless of display format, presenting real foods may nevertheless increase valuation and encourage healthy dietary choices.

The impact of a low-carbohydrate nutrition education program on food preferences: The correspondence between self-report consumption and supermarket purchases

There is reasonable concern that self-reported nutrition assessments do not reflect actual food choices. Yet, a correspondence between both is imperative to evaluate any intervention on food preferences. This paper makes such a comparison. It provides evidence from a low-carbohydrate nutrition education program, which is assessed with both surveys and an incentivized behavioral measure of food choice. The main result is that there is a large correspondence between survey and behavioral measures for our sample of 95 women from two historically underprivileged communities in the Western Cape, South Africa. Compared to the control, the treatment group reported a 35% lower intake from the high-carbohydrate/ ultra-processed food Red List and 60% higher intake from the low-carbohydrate whole foods Green List. The treatment group was also 40% less likely to buy anything from the Red List with a supermarket voucher. In terms of the Green List, the treatment group was significantly more likely to buy eggs, organ meat, traditional fats, avocado and fish but there was no difference in red meat and chicken, non-starchy vegetables and full cream dairy. Low-cost incentivized measures of revealed preferences can be designed to validate subjective habits, increasing confidence in the quality of evidence from nutrition intervention studies.

Hypothalamic volume is associated with body mass index

The hypothalamus is an important neuroendocrine hub for the control of appetite and satiety. In animal studies it has been established that hypothalamic lesioning or stimulation causes alteration to feeding behaviour and consequently body mass, and exposure to high calorie diets induces hypothalamic inflammation. These findings suggest that alterations in hypothalamic structure and function are both a cause and a consequence of changes to food intake. However, there is limited in vivo human data relating the hypothalamus to obesity or eating disorders, in part due to technical problems relating to its small size. Here, we used a novel automated segmentation algorithm to exploratorily investigate the relationship between hypothalamic volume, normalised to intracranial volume, and body mass index (BMI). The analysis was applied across four independent datasets comprising of young adults (total n = 1,351 participants) spanning a range of BMIs (13.3 - 47.8 kg/m2). We compared underweight (including individuals with anorexia nervosa), healthy weight, overweight and obese individuals in a series of complementary analyses. We report that overall hypothalamic volume is significantly larger in overweight and obese groups of young adults. This was also observed for a number of hypothalamic sub-regions. In the largest dataset (the HCP-Young Adult dataset (n = 1111)) there was a significant relationship between hypothalamic volume and BMI. We suggest that our findings of a positive relationship between hypothalamic volume and BMI is potentially consistent with hypothalamic inflammation as seen in animal models in response to high fat diet, although more research is needed to establish a causal relationship. Overall, we present novel, in vivo findings that link elevated BMI to altered hypothalamic structure. This has important implications for study of the neural mechanisms of obesity in humans.

Can we have a second helping? A preregistered direct replication study on the neurobiological mechanisms underlying self-control

Self‐control is of vital importance for human wellbeing. Hare et al. (2009) were among the first to provide empirical evidence on the neural correlates of self‐control. This seminal study profoundly impacted theory and empirical work across multiple fields. To solidify the empirical evidence supporting self‐control theory, we conducted a preregistered replication of this work. Further, we tested the robustness of the findings across analytic strategies. Participants underwent functional magnetic resonance imaging while rating 50 food items on healthiness and tastiness and making choices about food consumption. We closely replicated the original analysis pipeline and supplemented it with additional exploratory analyses to follow‐up on unexpected findings and to test the sensitivity of results to key analytical choices. Our replication data provide support for the notion that decisions are associated with a value signal in ventromedial prefrontal cortex (vmPFC), which integrates relevant choice attributes to inform a final decision. We found that vmPFC activity was correlated with goal values regardless of the amount of self‐control and it correlated with both taste and health in self‐controllers but only taste in non‐self‐controllers. We did not find strong support for the hypothesized role of left dorsolateral prefrontal cortex (dlPFC) in self‐control. The absence of statistically significant group differences in dlPFC activity during successful self‐control in our sample contrasts with the notion that dlPFC involvement is required in order to effectively integrate longer‐term goals into subjective value judgments. Exploratory analyses highlight the sensitivity of results (in terms of effect size) to the analytical strategy, for instance, concerning the approach to region‐of‐interest analysis.

In vivo neuroimaging evidence of hypothalamic alteration in Prader–Willi syndrome

Prader–Willi syndrome is a genetic neurodevelopmental disorder with an early phenotype characterized by neonatal hypotonia, failure to thrive, and immature genitalia. The onset of hyperphagia in childhood and developmental, physical and neuropsychiatric characteristics indicate atypical brain development and specifically hypothalamic dysfunction. Whether the latter is a consequence of disruption of hypothalamic pathways for genetic reasons or due to a failure of hypothalamic development remains uncertain. Twenty participants with Prader–Willi syndrome, 40 age-matched controls and 42 obese participants underwent structural MRI scanning. The whole hypothalamus and its subnuclei were segmented from structural acquisitions. The Food-Related Problem Questionnaire was used to provide information relating to eating behaviour. All hypothalamic nuclei were significantly smaller in the Prader–Willi group, compared with age and gender matched controls (P < 0.01) with the exception of the right anterior–inferior nucleus (P = 0.07). Lower whole hypothalamus volume was significantly associated with higher body mass index in Prader–Willi syndrome (P < 0.05). Increased preoccupation with food was associated with lower volumes of the bilateral posterior nuclei and left tubular superior nucleus. The whole hypothalamus and all constituent nuclei were also smaller in Prader–Willi syndrome compared with obese participants (P < 0.001). Connectivity profiles of the hypothalamus revealed that fractional anisotropy was associated with impaired satiety in Prader–Willi syndrome (P < 0.05). We establish that hypothalamic structure is significantly altered in Prader–Willi syndrome, demonstrating that hypothalamic dysfunction linked to eating behaviour is likely neurodevelopmental in nature and furthermore, distinctive compared with obesity in the general population.

Body Positivity, but not for everyone: The role of model size in exposure effects on women's mood, body satisfaction, and food choice

Body Positivity (or 'BoPo') social media content may be beneficial for women's mood and body image, but concerns have been raised that it may reduce motivation for healthy behaviours. This study examines differences in women's mood, body satisfaction, and hypothetical food choices after viewing BoPo posts (featuring average or larger women) or a neutral travel control. Women (N = 167, 81.8 % aged 18-29) were randomly assigned in an online experiment to one of three conditions (BoPo-average, BoPo-larger, or Travel/Control) and viewed three Instagram posts for two minutes, before reporting their mood and body satisfaction, and selecting a meal from a hypothetical menu. Women who viewed the BoPo posts featuring average-size women reported more positive mood than the control group; women who viewed posts featuring larger women did not. There were no effects of condition on negative mood or body satisfaction. Women did not make less healthy food choices than the control in either BoPo condition; women who viewed the BoPo images of larger women showed a stronger association between hunger and calories selected. These findings suggest that concerns over BoPo promoting unhealthy behaviours may be misplaced, but further research is needed regarding women's responses to different body sizes.

Problematic eating as an issue of habitual control

Obesity has reached alarming rates worldwide. Although many people attempt to control weight by modifying their food-related behaviours, this typically only has short-term effects and most dieters regain the weight that was lost. Why do so many people struggle to regulate their food-related behaviours? One possible explanation is that these behaviours have become habits that are not immediately sensitive to their consequences. Here we review experimental evidence for a shift to habitual control over food-related behaviours and the neural systems that control them and how this relates to difficulty changing ones' eating behavior.

The Treachery of Images: How Realism Influences Brain and Behavior

Although the cognitive sciences aim to ultimately understand behavior and brain function in the real world, for historical and practical reasons, the field has relied heavily on artificial stimuli, typically pictures. We review a growing body of evidence that both behavior and brain function differ between image proxies and real, tangible objects. We also propose a new framework for immersive neuroscience to combine two approaches: (i) the traditional build-up approach of gradually combining simplified stimuli, tasks, and processes; and (ii) a newer tear-down approach that begins with reality and compelling simulations such as virtual reality to determine which elements critically affect behavior and brain processing.

A review on food recognition technology for health applications

Food understanding from digital media has become a challenge with important applications in many different domains. On the other hand, food is a crucial part of human life since the health is strictly affected by diet. The impact of food in people life led Computer Vision specialists to develop new methods for automatic food intake monitoring and food logging. In this review paper we provide an overview about automatic food intake monitoring, by focusing on technical aspects and Computer Vision works which solve the main involved tasks (i.e., classification, recognitions, segmentation, etc.). Specifically, we conducted a systematic review on main scientific databases, including interdisciplinary databases (i.e., Scopus) as well as academic databases in the field of computer science that focus on topics related to image understanding (i.e., recognition, analysis, retrieval). The search queries were based on the following key words: "food recognition", "food classification", "food portion estimation", "food logging" and "food image dataset". A total of 434 papers have been retrieved. We excluded 329 works in the first screening and performed a new check for the remaining 105 papers. Then, we manually added 5 recent relevant studies. Our final selection includes 23 papers that present systems for automatic food intake monitoring, as well as 46 papers which addressed Computer Vision tasks related food images analysis which we consider essential for a comprehensive overview about this research topic. A discussion that highlights the limitations of this research field is reported in conclusions.

Food Folio by Columbia Center for Eating Disorders: A Freely Available Food Image Database

Food images are useful stimuli for the study of cognitive processes as well as eating behavior. To enhance rigor and reproducibility in task-based research, it is advantageous to have stimulus sets that are publicly available and well characterized. Food Folio by Columbia Center for Eating Disorders is a publicly available set of 138 images of Western food items. The set was developed for the study of eating disorders, particularly for use in tasks that capture eating behavior characteristic of these illnesses. It contains foods that are typically eaten, as well as those typically avoided, by individuals with eating disorders. Each image has now been rated across 17 different attributes by a large general United States population sample via Amazon's Mechanical Turk (n = 1054). Ratings included subjective attributes (e.g., tastiness, healthiness, and favorable texture) as well as estimates of nutrient content (e.g., fat and carbohydrate). Each participant rated a subset of stimulus set food items (46 foods) on all 17 dimensions. Additional description of the image set is provided in terms of physical image information and accurate nutritional information. Correlations between subjective ratings were calculated and an exploratory factor analysis and exploratory cluster analysis completed. Outcomes of the factor analysis suggested foods may be described along three latent factors of healthiness, tastiness, and umami taste; the cluster analysis highlighted five distinct clusters of foods varying on these same dimensions. Descriptive outcomes indicated that the stimulus set includes a range of foods that vary along multiple dimensions and thus is likely to be useful in addressing various research questions surrounding eating behavior and cognition in healthy populations, as well as in those with eating disorders. The provision of comprehensive descriptive information allows for stimulus selection that is optimized for a given research question and promotes strong inference.

Relating goal-directed behaviour to grazing in persons with obesity with and without eating disorder features

BACKGROUND

Both obesity and eating disorders (ED) have been associated with reductions in purposeful, flexible goal-directed behaviour, and with an overreliance on more rigid habitual behaviour. It is currently unknown whether grazing, an eating style which is common in both conditions, is related to goal-directed behaviour. The current study therefore aimed to relate grazing to goal-directed behaviour in a group of participants with obesity with and without ED features, compared to a healthy-weight control group.

METHODS

Participants (N = 87; 67.8% women, mean age 28.57 years), of whom 19 had obesity and significant eating disorder features, 25 had obesity but without marked eating disorder features, and 43 were age- and sex-matched healthy-weight controls, completed two instrumental learning tasks assessing action-outcome contingency sensitivity and devaluation sensitivity, as well as demographic and eating disorder-related questionnaires. Gamma and Ordinary Least Squares regressions were performed to examine the effect of group and grazing on goal-directed behaviour.

RESULTS

Lower action-outcome contingency sensitivity was found in the group with obesity and with eating disorder features than in the group with obesity but without eating disorder features or in healthy controls. No group differences in devaluation sensitivity were found. A small but significant relationship was found between grazing severity and contingency sensitivity in the group with obesity and eating disorder features, such that increasing grazing severity was associated with less diminished contingency sensitivity.

CONCLUSIONS

There is some indication that in persons with obesity and eating disorder features instrumental behaviour is less flexible and adaptive; furthermore, within this group grazing may represent a goal-directed behaviour, despite unhelpful long-term implications of grazing.

Touch for Health: Use of Pavlovian Processes with Physical Touch as a Means to Improve Menstrual Hygiene Management Initiatives, Measured by Willingness to Pay

BACKGROUND

To combat the lack of proper facilities and menstrual health knowledge in developing countries, many WASH (Water, Hygiene, and Sanitation) initiatives are including menstrual hygiene management (MHM) components. However, evidence shows that prior efforts have not been ultimately successful in inducing relevant behavior changes, due in part to cultural constraints and unidimensional interventions. As such, MHM research may need to include consideration of new theories/approaches. Evidence is growing of the role that physical presence/proximity and ability to touch objects has on incentives for consumers to purchase goods, captured through willingness to pay (WTP) figures. Such findings can be partially explained by Pavlovian processes.

OBJECTIVE

This study sought to provide field-work validation of such findings of the role of Pavlovian processes and endowment effect on WTP figures for a female hygiene kit, reflecting motivation to adopt better hygiene behaviors.

METHODS

This study used primary survey data collected from females in two upper-level schools in southwestern Nepal (n = 169). When presented in conjunction with a hygiene education session, one group of females was allowed physical interaction with a female hygiene kit, while another was not, before being surveyed on their WTP for the kit. Both non-parametric and parametric statistical analyses were performed to assess the impact of this ability to touch the kits on WTP figures.

RESULTS

Results show a statistically significant difference between the WTP figures of those females allowed interaction with the kits prior to being surveyed and those who did not. This confirms the positive impact of physical presence/touch on motivations to use/acquire hygiene-related tools.

CONCLUSIONS

Such findings reveal how, through application of the theory of Pavlovian processes, future (menstrual) health education efforts could harness the human instinct to consume, remember, and use those objects presented in physical form, and include personal contact and demonstrations of better health practices in future MHM and WASH education initiatives. Such an approach may allow protocols and interventions to have more success, and dissemination of healthier behaviors and knowledge to be more prominent.

Effect of Impulsivity Traits on Food Choice within a Nudging Intervention

Food choices are often driven by impulsive tendencies rather than rational consideration. Some individuals may find it more difficult resisting impulses related to unhealthy food choices, and low self-control and high impulsivity have been suggested to be linked to these behaviors. Recent shifts have been made towards developing strategies that target automatic processes of decision-making and focus on adjusting the environment, referred to as nudging interventions. Therefore, the purpose of this study was to investigate the effect of impulsivity traits on food choices within a nudging intervention (increased perceived variety). A total of 83 adults participated in an experimental study consisting of a self-service intelligent buffet. Impulsivity traits were measured using the UPPS-P impulsivity scale. General linear models were fitted to evaluate the effect of the five impulsivity traits on the difference of salad consumption (g) between the control and intervention situations. Results showed that impulsivity does not affect food choices in this nudging situation, suggesting that nudging works independently of the participant's impulsivity score. Results also showed a significantly higher consumption of salad in the nudging versus the control setting (17.6 g, p < 0.05), suggesting that nudging interventions can be effective in significantly increasing total vegetable consumption across the whole impulsivity scale.

Rethinking Food Reward

The conscious perception of the hedonic sensory properties of caloric foods is commonly believed to guide our dietary choices. Current and traditional models implicate the consciously perceived hedonic qualities of food as driving overeating, whereas subliminal signals arising from the gut would curb our uncontrolled desire for calories. Here we review recent animal and human studies that support a markedly different model for food reward. These findings reveal in particular the existence of subcortical body-to-brain neural pathways linking gastrointestinal nutrient sensors to the brain's reward regions. Unexpectedly, consciously perceptible hedonic qualities appear to play a less relevant, and mostly transient, role in food reinforcement. In this model, gut-brain reward pathways bypass cranial taste and aroma sensory receptors and the cortical networks that give rise to flavor perception. They instead reinforce behaviors independently of the cognitive processes that support overt insights into the nature of our dietary decisions.

A review of evidence supporting current strategies, challenges, and opportunities to reduce portion sizes

Although there is considerable evidence for the portion-size effect and its potential impact on health, much of this has not been successfully applied to help consumers reduce portion sizes. The objective of this review is to provide an update on the strength of evidence supporting strategies with potential to reduce portion sizes across individuals and eating contexts. Three levels of action are considered: food-level strategies (targeting commercial snack and meal portion sizes, packaging, food labels, tableware, and food sensory properties), individual-level strategies (targeting eating rate and bite size, portion norms, plate-cleaning tendencies, and cognitive processes), and population approaches (targeting the physical, social, and economic environment and health policy). Food- and individual-level strategies are associated with small to moderate effects; however, in isolation, none seem to have sufficient impact on food intake to reverse the portion-size effect and its consequences. Wider changes to the portion-size environment will be necessary to support individual- and food-level strategies leading to portion control.

Health, pleasure, and fullness: changing mindset affects brain responses and portion size selection in adults with overweight and obesity

BACKGROUND

Increased portion size is an essential contributor to the current obesity epidemic. The decision of how much to eat before a meal begins (i.e. pre-meal planning), and the attention assigned to this task, plays a vital role in our portion control.

OBJECTIVE

We investigated whether pre-meal planning can be influenced by a shift in mindset in individuals with overweight and obesity in order to influence portion size selection and brain activity.

DESIGN

We investigated the neural underpinnings of pre-meal planning in 36 adults of different weight groups (BMI < 25 kg/m² and BMI ≥ 25 kg/m²) by means of functional magnetic resonance imaging. To examine the important role of attentional focus, participants were instructed to focus their mindset on the health effects of food, expected pleasure, or their intention to stay full until dinnertime, while choosing their portion size for lunch.

RESULTS

We observed that participants of all weight groups reduced their portion size when adopting a health mindset, which was accompanied by enhanced activation of the self-control network (i.e. left prefrontal cortex). Fullness and pleasure mindsets resulted in contrasting reward responses in individuals with overweight and obesity compared to normal-weight individuals. Under the pleasure mindset, persons with overweight and obesity showed heightened activity in parts of the taste cortex (i.e. right frontal operculum), while the fullness mindset caused reduced activation in the ventral striatum, an important component of the reward system. Moreover, participants with overweight and obesity did not modify their behaviour under the pleasure mindset and selected larger portions than the normal-weight group.

CONCLUSIONS

We were able to identify specific brain response patterns as participants made a final choice of a portion size. The results demonstrate that different brain responses and behaviours during pre-meal planning can inform the development of effective strategies for healthy weight management.

The association between self-rated health and underlying biomarker levels is modified by age, gender, and household income: Evidence from Understanding Society - The UK Household Longitudinal Study

The goal of this study was to evaluate how self-rated health (SRH) and objective measures of health (biomarkers) are associated, and if this association varies by gender, age, and socioeconomic position (measured by household income). Data come from the UK Household Longitudinal Study nurse visit (2010–2012), including a representative sample of adults in Great Britain (N = 15 687 maximum sample). SRH was assessed by the question “In general, would you say your health is excellent, very good, good, fair, or poor?” and dichotomized into good or poor. Indices were created for four biomarker categories based on the aspects of health they are likely to reflect, including visible weigh-related, fitness, fatigue, and disease risk biomarkers. Logistic regression models were run with SRH as the outcome and each biomarker index as a predictor, adjusting by gender, age, and income. Further, interaction terms between each biomarker index and gender, age, and income (independently) were added to test for effect modification. All biomarker indices were associated with SRH in expected directions, with the fitness index most strongly predicting SRH. Gender, age, or income modified the associations between SRH and all biomarker indices to different extents. The association between the visible weight-related biomarker index (including body mass/fat variables) and SRH was stronger for women than men and for those in higher income groups than lower income groups. Income also modified the association between SRH and the fitness biomarker index, whereas age modified the association between SRH and the fatigue biomarker index. When using SRH to investigate health inequalities, researchers and policy makers should be clear that different social groups may systematically consider different dimensions of health when reporting their SRH.

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The association between self-rated global health and underlying objective health as measured by biomarkers varies by type of biomarker, age, sex and socioeconomic status.

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Biomarkers that measure different aspects of fitness most strongly predicting self-rated health.

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The association between the visible biomarkers (including body mass/fat variables) and self-rated health was stronger for women than men and for those in higher income groups than lower income groups.

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Income also modified the association between self-rated health and biomarkers of disease, with a stronger association for higher income groups.

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When rating own health individuals from different social groups may systematically consider different dimensions of health.

A neural basis for food foraging in obesity

Poverty-related food insecurity can be viewed as a form of economic and nutritional uncertainty that can lead, in some situations, to a desire for more filling and satisfying food. Given the current obesogenic food environment and the nature of the food supply, those food choices could engage a combination of sensory, neurophysiological, and genetic factors as potential determinants of obesity.

Modulation of midbrain neurocircuitry by intranasal insulin

Insulin modulates dopamine neuron activity in midbrain and affects processes underlying food intake behaviour, including impulsivity and reward processing. Here, we used intranasal administration and task-free functional MRI in humans to assess time- and dose-dependent effects of insulin on functional connectivity of the dopaminergic midbrain - and how these effects varied depending on systemic insulin sensitivity as measured by HOMA-IR. Specifically, we used a repeated-measures design with factors dose (placebo, 40 IU, 100 IU, 160 IU), time (7 time points during a 90 min post-intervention interval), and group (low vs. high HOMA-IR). A factorial analysis identified a three-way interaction (with whole-brain significance) with regard to functional connectivity between midbrain and the ventromedial prefrontal cortex. This interaction demonstrates that systemic insulin sensitivity modulates the temporal course and dose-dependent effects of intranasal insulin on midbrain functional connectivity. It suggests that altered insulin sensitivity may impact on dopaminergic projections of the midbrain and might underlie the dysregulation of reward-related and motivational behaviour in obesity and diabetes. Perhaps most importantly, the time courses of midbrain functional connectivity we present may provide useful guidance for the design of future human studies that utilize intranasal insulin administration.

Good practice in food-related neuroimaging

The use of neuroimaging tools, especially functional magnetic resonance imaging, in nutritional research has increased substantially over the past 2 decades. Neuroimaging is a research tool with great potential impact on the field of nutrition, but to achieve that potential, appropriate use of techniques and interpretation of neuroimaging results is necessary. In this article, we present guidelines for good methodological practice in functional magnetic resonance imaging studies and flag specific limitations in the hope of helping researchers to make the most of neuroimaging tools and avoid potential pitfalls. We highlight specific considerations for food-related studies, such as how to adjust statistically for common confounders, like, for example, hunger state, menstrual phase, and BMI, as well as how to optimally match different types of food stimuli. Finally, we summarize current research needs and future directions, such as the use of prospective designs and more realistic paradigms for studying eating behavior.

Satiety-induced enhanced neuronal activity in the frontal operculum relates to the desire for food in the obese female brain

In the present pilot study, we questioned how eating to satiety affects cognitive influences on the desire for food and corresponding neuronal activity in the obese female brain. During EEG recording, lean (n = 10) and obese women (n = 10) self-rated the ability to reappraise visually presented food. All women were measured twice, when hungry and after eating to satiety. After eating to satiety, reappraisal of food was easier than when being hungry. Comparing the EEG data of the sated to the hungry state, we found that only in obese women the frontal operculum was involved not only in the reappraisal of food but also in admitting the desire for the same food. The right frontal operculum in the obese female brain, assumed to primarily host gustatory processes, may be involved in opposing cognitive influences on the desire for food. These findings may help to find potential brain targets for non-invasive brain stimulation or neurofeedback studies that aim at modulating the desire for food.

The real deal: Willingness-to-pay and satiety expectations are greater for real foods versus their images

Laboratory studies of human dietary choice have relied on computerized two-dimensional (2D) images as stimuli, whereas in everyday life, consumers make decisions in the context of real foods that have actual caloric content and afford grasping and consumption. Surprisingly, few studies have compared whether real foods are valued more than 2D images of foods, and in the studies that have, differences in the stimuli and testing conditions could have resulted in inflated bids for the real foods. Moreover, although the caloric content of food images has been shown to influence valuation, no studies to date have investigated whether 'real food exposure effects' on valuation reflect greater sensitivity to the caloric content of real foods versus images. Here, we compared willingness-to-pay (WTP) for, and expectations about satiety after consuming, everyday snack foods that were displayed as real foods versus 2D images. Critically, our 2D images were matched closely to the real foods for size, background, illumination, and apparent distance, and trial presentation and stimulus timing were identical across conditions. We used linear mixed effects modeling to determine whether effects of display format were modulated by food preference and the caloric content of the foods. Compared to food images, observers were willing to pay 6.62% more for (Experiment 1) and believed that they would feel more satiated after consuming (Experiment 2), foods displayed as real objects. Moreover, these effects appeared to be consistent across food preference, caloric content, as well as observers' estimates of the caloric content of the foods. Together, our results confirm that consumers' perception and valuation of everyday foods is influenced by the format in which they are displayed. Our findings raise important new insights into the factors that shape dietary choice in real-world contexts and highlight potential avenues for improving public health approaches to diet and obesity.

Brain substrates of unhealthy versus healthy food choices: influence of homeostatic status and body mass index

BACKGROUND/OBJECTIVES

Unhealthy dietary choices are a major contributor to harmful weight gain and obesity. This study interrogated the brain substrates of unhealthy versus healthy food choices in vivo, and evaluated the influence of hunger state and body mass index (BMI) on brain activation and connectivity.

SUBJECTS/METHODS

Thirty adults (BMI: 18-38 kg m^-2) performed a food-choice task involving preference-based selection between beverage pairs consisting of high-calorie (unhealthy) or low-calorie (healthy) options, concurrent with functional magnetic resonance imaging (fMRI). Selected food stimuli were delivered to participants using an MRI-compatible gustometer. fMRI scans were performed both after 10-h fasting and when sated. Brain activation and hypothalamic functional connectivity were assessed when selecting between unhealthy-healthy beverage pairings, relative to unhealthy-unhealthy and healthy-healthy options. Results were considered significant at cluster-based family-wise error corrected P<0.05.

RESULTS

Selecting between unhealthy and healthy foods elicited significant activation in the hypothalamus, the medial and dorsolateral prefrontal cortices, the anterior insula and the posterior cingulate. Hunger was associated with higher activation within the ventromedial and dorsolateral prefrontal cortices, as well as lower connectivity between the hypothalamus and both the ventromedial prefrontal cortex and dorsal striatum. Critically, people with higher BMI showed lower activation of the hypothalamus-regardless of hunger state-and higher activation of the ventromedial prefrontal cortex when hungry.

CONCLUSIONS

People who are overweight and obese have weaker activation of brain regions involved in energy regulation and greater activation of reward valuation regions while making choices between unhealthy and healthy foods. These results provide evidence for a shift towards hedonic-based, and away from energy-based, food selection in obesity.