Diet and Sensory-Perception

The consumption of palatable, energy-dense foods, driven by their enhanced taste, is known to impact overall health negatively. A thorough understanding of the links between taste and food choices can help shed light on the mechanisms behind food preferences. In this review by Liem and Russell (2019), the authors sought to investigate three main queries, firstly: whether the taste profiles of nutrient-rich food differ from those of nutrient-poor foods, secondly, whether a predisposition exists to increase the propensity of nutrient-rich food preference, and finally, whether these preferences and predispositions are influenced by negative health outcomes or chronic intake of nutrient-rich foods. Analysis of the results revealed that individuals varied in their taste preferences, despite an overall predilection for sweet tastes and antipathy to bitter tastes, which may partially explain the short-term preferences for food. Current observations noted that nutrient-rich foods had several taste profiles, while nutrient-poor foods were more likely to have fatty, sweet, and salty taste profiles. Finally, the authors conclude that available evidence has failed to investigate the links between negative health outcomes related to food consumption (such as obesity) and the long-term choices of food, raising the need to conduct further studies on smell, taste, texture and the full spectrum of sensations evoked by food and how they impact the individual experience in consuming nutrient-rich or nutrient-poor foods, influencing factors such as food choices, dietary preferences, and health motivations. [NPID: Taste, consumer choices, sensory profile, food, nutrition]

Visual input impacts our perception of taste so much that it plays a key role in our overall appreciation of daily life, as evidenced by appetite scientific research. In this study by Kokaji & Nakatani (2021), the authors investigated the impact of visual data resulting from food presented on a plate on stimulating a multifaceted mental image, in addition to how garnishing on a plate (being a source of peripheral visual data) influences the viewer’s impression of the quality of the main dish, in a population of 15 individuals (four men, mean age = 22 ± 1.37 years). The participants were subjected to a series of food photographs and had their food impressions noted, revealing that the use of garnishing in proximity to the main dish enhances the appetite-stimulating effect of visual data. Furthermore, the participants reported increased acceptability of food depending on the appearance of warmth, moisture, color, and taste (spice, sour) of food. The authors comment that their results shed light on how appetite stimulation and the experience of eating may be enhanced to elevate the dining experience through using garnishing or through visual augmented reality technology. [NPID: Food pairing, food plating, image analysis, sensory science, visual perception]

Beautiful environments provide a coveted dining ambiance. Research has demonstrated the influence of the surrounding environment on personal food perceptions, however, the evidence on the impact of environmental aesthetics remains insufficient. Wu et al. (2022) conducted two experiments to evaluate this concept. In their first experiment, study participants were asked to evaluate the olfactory, visual, and taste of food presented in images, coupled with photographs representing a restaurant (1a) and a non-restaurant (1b) environment (high or low aesthetics). Analysis of participant ratings showed substantial elevation in all sensory modality ratings coupled with the high aesthetic environment, coupled with increased appetite and positive affect. In their second experiment, the authors applied a similar approach to physical environments (high and low aesthetics) and provided the participants with food. Similarly, the participants reported increased gustatory and olfactory scores, in addition to reports on participants’ desire to dine in the high aesthetic environment again, compared to the low aesthetic environment. The authors comment that their results demonstrate the impact of environmental aesthetics on food perceptions, and the role emotions play in the links between them. The authors conclude that their research helps shed light on methods to improve the positive perception of food. [NPID: Desire to eat, emotion, environmental aesthetic value, food perception]

In this study by Zhang et al. (2022), the authors investigate how the aesthetics in food plating influence our perception of food, motivated by the increasing level of interest in food aesthetics. Using a set of three experiments, the authors evaluated if variable levels of plate aesthetics (expressive, i.e. food that was creative and had an original design, versus classical, i.e. food that was neat, organized, and clean) and beauty play a role in the healthy and tasteful perception of food. In their first experiment, a sample of 30 participants was presented with food plates of different levels of beauty and aesthetic attention, resulting in an overall increased perception of healthier, tastier food on more beautiful plates. The second experiment revealed that, in a sample of 128 participants, plates focusing on expressive aesthetics invoked positive emotions if the plates were beautiful and negative emotions in plates that were less beautiful, an observation that was not seen in plates that focused on classical aesthetics. In their third experiment, which investigated food placement, the authors analyzed data from 149 participants, revealing an enhanced perception of taste to food placed at the center of the dish compared to food placed at the edge of the dish if the food was presented with a classical aesthetic. On the other hand, the placement of food in expressive aesthetic-focused plates did not impact how the participants perceived the food. The authors conclude that their results demonstrate how the beautiful patterns in plates play a role in how individuals perceive food, however, they also note that such perceptions are influenced by the aesthetics adopted in creating the plate pattern. [NPID: Aesthetic, food and health, plate pattern, plating]

This 2022 article exposes how the placement of food items on menus can have an influential role on people’s food choices. There were two studies conducted to determine which conditions affect the participants’ food decisions. Healthy items were placed on the top, middle, and bottom sections of the snack menu. The first study used a physical paper menu and consisted of 8 unhealthy and 4 healthy items, while the second study published online menus arranged in three rows of four. In each study, the subjects selected one food item from the three experimental menus, before completing the Revised Restraint Scale (a measure of dietary restraint). The food item conditions in study 1 did not appear to predict healthiness of food choice. On the other hand, study 2 demonstrated that people chose from the first section of the menu more often than from the middle or last sections. Dietary restraint did not moderate the effect of item placement conditions on food choice. It can be said that item placement techniques could represent a potentially powerful tool in promoting healthy food choices from online snack menus. [NPID: snacks, food choices, food decisions, item placement, perception, dietary restraint, menu, online menu, health promotion]

In this 2021 study, subjects were given placebo breakfasts with very low energy content to test its effect on appetite over time and on their food intake at lunch. A total of fourteen healthy males took part in this experiment. They were randomly assigned to one of three types of breakfasts: water only; a whole-food breakfast; or a very low-energy placebo version composed of flavored squash, and xanthan gum. The placebo breakfast contained around 16 kilocalories (kcal), while the whole-food breakfast had ~ 573 kcal. The study found that people who had the whole-food breakfast consumed less for lunch than individuals who were only given water for breakfast. In terms of total energy intake over both breakfast and lunch, those given the whole-food breakfast reported higher cumulated energy consumption than both the water-only and placebo groups. Higher total energy intake was seen in participants in the low-energy placebo group, compared with the water-only group (1554 kcal vs. 1093 kcal). This study concludes that eating a very low energy placebo breakfast did not affect how much the participants ate for lunch but could reduce the total energy accumulated over breakfast and lunch. Having a low-energy breakfast may also help lessen the appetite jump they would hypothetically experience if they skipped breakfast. [NPID: skipping breakfast, water, placebo, low energy breakfast, perception, energy intake, eating, guidelines, calories, kilocalories]

While the color of food items is said to affect dietary behaviors, this 2014 study examines the possible effects of meal variety and the color arrangement of the food. These variables may influence how pleasant the food is for the consumer over time, and potentially consumption behavior. While repeated intake of the same foods can lead to a decrease in perceived pleasantness, variation within a meal has been shown to slow down this process. This present review looks at research papers written on how general meal variety determines these variables, and on the major theories that have been put forward by researchers to explain them. This review analyzes the evidence on the impact that color may have on eating behavior and sensory-specific satiety (the reduction in pleasantness of the food as it is consumed). Lastly, this paper explains the results of these research studies, including those supportive and non-supportive of the major theories. [NPID: color, food color, eating behavior, review, literature review, perception, pleasantness, taste, sensory-specific satiety]

This 2021 study explores the effect of food variety on eating via sensory-specific satiety, which is the relative reduction in pleasantness of a food as it is eaten. There was a total of 118 participants, divided into one of four conditions. In each condition, subjects were allowed to eat a specific food item until full. In the next stage, they were given either the same or a different food in either the same context or in a different context. The study authors hypothesized that introducing a new food item or changing the context for the second course would increase food consumption of the second course, compared with eating the same food in the same context. Moreover, Hendriks et al. predicted that making modifications to both food and context would enhance food intake to a greater degree than only changing one of the variables (food or context). The results demonstrated that presenting a different food item significantly increased eating in the second course. However, the adjustment in context did not positively influence consumption. This study suggests that sensory-specific satiety may not be context-specific. [NPID: food context, perception, sensory-specific satiety, food variety, variation, change]

The goal for this 2012 study was to uncover the connection between genetic predisposition, dietary habits, and feeding disorders. Scientists analyzed saliva samples of the participants to examine the genetic variations in a specific bitter receptor. The study then assessed whether there was a correlation between genetic variations in this receptor with food choices. The plan was to measure taste sensitivity in healthy adults and their children, and to evaluate the taste sensitivity of children with obesity and those affected by functional gastrointestinal diseases. Adults, parents, and children were recruited from the general population in southern Italy. A difference in taste sensitivity was discovered between the children and the adults. Moreover, the prevalence rate of supertasters was much higher in the children than the adults. This trend was also observed when comparing mothers and their child even though they shared the same diplotypes (subsets of all genotypes on homologous chromosome pairs). Supertaster status was associated with having identical taste alleles among adults, whereas most of the children showed two different alleles in the same haplotype. Furthermore, a higher proportion of taster children avoided bitter vegetables altogether compared with taster adults. There was another relationship found among just the boys between taster status and body mass index. In conclusion, greater sensitivity to 6-propyl-2-thiouracil (the assessment of bitterness sensitivity) predicted lower preferences for vegetables in children. This signifies the extent to which genetic predisposition influences food choices. [NPID: food choice, genetics, dietary habits, diet, genes, children, perception, taste perception, taste sensitivity, bitterness, bitter taste, bitter sensitivity, Italy, Italians, obesity]

The aim of this 2020 systematic review was to evaluate the extent to which food texture influences how “full” one feels after eating. Satiety is the name given to the state of being “full”. Scientists are looking into the potential use of satiety-enhancing foods in reducing food consumption and promoting weight loss. This study may have great health implications since obesity is one of the leading causes of preventable deaths. The results showed that solid and more viscous foods reduced hunger to a greater extent compared with liquid and less viscous foods. Food viscosity increased fullness, whereas food intake was slightly reduced by the form of food. Due to the large variation among the analyzed studies, these results should be interpreted with caution. [NPID: food texture, food viscosity, satiety, review, hunger, obesity, fullness, weight loss]

Since the majority of the evidence on the association between the quality of the American diet and advertising has been reported in children, Zimmerman & Shimoga (2014) planned to determine the impact that televised advertising has on adults’ food choices. The 351 participants were firstly randomized into one of four groups: exposed to food advertising and a cognitively challenging task; food advertising encounter and non-cognitively demanding task; seeing advertising that are non-food related and performing a cognitively tough task; or viewing non-food advertising before performing a non-cognitively straining task. The outcomes measured were the number and calorie contents of the unhealthy snacks selected by the subjects. The data revealed that those exposed to food advertising chose 28% more unhealthy snacks than those who encountered non-food advertising. Moreover, the caloric values of these snacks chosen by the food advertising-exposed half of the sample were 65 kcal higher. The different adverts did not significantly affect the individuals assigned to the less cognitively demanding task, but there was a large and significant discrepancy in influence among the participants that completed cognitively challenging tasks. Those who came across food-related adverts ate 43% more unhealthy snacks, taking in 94 more total calories, compared to the subjects who saw non-food adverts. This research concludes that televised food advertising strongly influences people’s food choices, particularly when these individuals are cognitively occupied. [NPID: perception, advertising, children, food choices, decision-making, cognition, television]

With the aim of better understanding the role of odors in overeating, Zoon (2017) found that smelling food odors increases appetite for foods similar in taste and energy density to that odor, and decreases the liking and desire for these congruent foods. This article also reveals that following high energy/sweet food consumption, early neural processing of pictures of the same foods changed significantly. Conversely, smelling odors signalling high-energy food, low-energy food, and non-foods did not lead to alterations in food preferences or intakes. But the researchers learnt that patients who undergo Roux-en-Y Gastric Bypass (RYGB) weight-loss surgery start to prefer low-fat/low-sugar foods rather than their previously preferred diet of high-fat/high-sugar foods. In addition, differences in prefrontal neural responses were seen in post-surgery patients, indicating inhibition of response to pictures of high-energy foods. These findings suggest that RYGB weight-loss surgery results in cognitive modifications (control of attention, neural inhibition over behavioral responses). It is therefore concluded that odors have an appetizing function in the anticipatory phase of eating, which implicates orthonasal odors in guiding people’s food decisions towards a healthier eating pattern. [NPID: perception, food odor, overeating, prefrontal neural responses, cognition, control of attention, attention, neural inhibition, behavioral response, anticipation, food decisions]

The aim of this 2008 experiment was to evaluate the impact of altering food viscosity on food intake (when given unrestricted access) in a real-life setting, and to assess whether a difference in consumption is related to either eating rate or effort. While 108 participants were placed in a real-life setting and given a chocolate flavored liquid, semi-liquid and semi-solid milk-based product (all similar in palatability, macronutrient composition and energy density), 49 subjects consumed the liquid or semi-solid product in the laboratory. The outcome measures were eating rate and effort, which could be determined by feeding the product through a peristaltic pump. The liquid form was reported to have been consumed the most in the real-life scenario at 809+/-396 g, which was 14% more than the semi-liquid, and 30% more compared to semi-solids. Disregarding eating effort in the laboratory setting resulted in a 29% higher intake of the liquid product relative to that of the semi-solid form. Standardizing the eating rate reduced this difference in consumption of the liquid and semi-solid test samples to 12%. If controls were not considered, the variation in quantity eaten between liquids and semi-solids was comparable to the real-life setting. In summary, the level of food consumption is greatly affected by viscosity, even if similar in palatability, macronutrient composition and energy density. The higher eating rates of liquids may play a factor in the difference in consumption observed. [NPID: perception, altered food viscosity, viscosity, food viscosity, liquid calories, chewing, oral processing, highly palatable foods, macronutrient composition, energy density]

Ziaduddeen et al. (2012) claim that although hunger may be reduced by the sensory-specific satiety (SSS) phenomenon (which describes the decline in satisfaction gained of the food being eaten relative to another type of food that has not been consumed), certain foods such as desserts remain attractive and encourage energy intake. Since it is important to understand how the dynamics between internal and external driving factors related to eating, this present study was designed to determine whether food stimuli would still induce the same effect even when they are subliminally communicated (unconsciously perceived), and whether this involuntary influence would vary in response to food reward value while sated (full). The results of this study indicate that the SSS phenomenon impact is unaffected by the lack of conscious awareness of external stimuli. Thus, our desire for food appears to be influenced by even the most subtle and subliminal events that take place around us. [NPID: perception, food reward value, satiety, reward, external eating, subliminal events, unconscious]

In this 2016 article, Wilkinson & Brunstrom firstly explain the popular belief that sensory specific satiety (the decline in pleasantness associated with a food as it is eaten relative to a food that has not been eaten) is controlled by habituation. Three experiments were conducted to evaluate whether 'top-down' cognitive activity has an effect on expression of sensory specific satiety (SSS). Participants were manipulated on their expectations on whether or not they would have access to alternative test foods (uneaten foods) after consuming a test meal (eaten food). Their desire to eat and pleasantness of the eaten food were thought to drop significantly more when uneaten foods were not available, but none of the findings backed up this hypothesis. Sensory specific satiety was not found to depend on top-down processes associated with the availability of other uneaten test foods. [NPID: perception, sensory specific satiety, satiety, habituation, top-down cognitive process, top-down, SSS, food pleasure]

While the global food companies are blamed for their role in the growing obesity crisis due to their provision of addictive foods and delivering of easily accessible calorie-rich foods, Spence et al. (2016) investigate whether there are other implicit cues in our environments that are increasing our hunger for foods. Compared to the environments our brains evolved, our current surroundings and especially in the Western world, dietary resources are much more readily available. While the food industry aims to design the perfect concoction of pleasurable ingredients (sugar, salt, fat, etc.), the authors want to analyze the digital impact of constantly viewing images of desirable foods (often labelled “gastroporn” or “food porn”). Our exposure to these pictures may be inadvertently heightening our desire for food. This article reviews the current evidence on the influence of these food images on neural activity, physiological and psychological responses, and visual attention, especially in the 'hungry' brain. [NPID: perception, obesity, obesity crisis, addictive foods, highly palatable foods, Western-style diet, WS diet, food industry, food desire, craving, visual attention]

Given the inconsistent findings on people’s detection speeds for food versus non-food items, Sawada et al. (2017) conducted a study assessing normal-weight individuals on their reaction times in detecting high-fat foods (fast food), low-fat foods (Japanese diet), and non-foods (kitchen utensils) among a crowd of cars (distractors). The researchers were interested in investigating the impact of fat content on food detection since fat content has been shown to affect visual attention for food in the past. The present study results backed up the evidence showing shorter reaction times for food targets than for non-food targets. Also, the participants reacted quicker to spot high-fat food items than low-fat foods. These findings suggest that food is more rapidly seen than non-foods and that higher fat content further speeds up the detection process. [NPID: perception, detection speed, reaction times, fat, visual attention, food targets]

Serrenho et al. (2019) describe ghrelin as an appetite-stimulating hormone produced by peripheral organs that play a part in signaling pathways when the energy status of the body changes, and regulate food intake, body weight, and glucose homeostasis. It has also been claimed by research studies that ghrelin is involved in cognition, and hedonic (pleasure-related) and homeostatic feeding. Since ghrelin-induced synaptic plasticity has been mentioned in neuronal circuits associated with aforementioned behaviors, this review inspected the neuromodulatory mechanisms induced by ghrelin in regulating synaptic plasticity in the circuits previously linked with feeding behaviors. As well as its connection with feeding behaviors, modified ghrelin concentrations is believed to correlate with metabolic disorders such as obesity and anorexia, emphasizing the importance of better understanding ghrelin and its impact on the synaptic plasticity of influential neuronal circuits. [NPID: perception, ghrelin, regulation, glucose homeostasis, cognition, hedonic, homeostatic feeding, plasticity, metabolic disorders, obesity, anorexia, neuronal circuits]

Although the processes behind the control of homeostatic feeding (required for basic metabolic processes and survival) and hedonic feeding (related to sensory perception or pleasure) are often considered separately, Rossi & Stuber (2018) believe there is a link between the two. Data indicate that many neural circuits that govern feeding behavior also are involved in the brain’s reward system (anatomically and functionally). Moreover, food consumption and reward can be influenced by altering several neural pathways. The authors ask their fellow researchers to look beyond food intake when investigating the neural control of feeding, and take into account other behaviors. This research is regarded to be crucial since the central regulation of food consumption is a key mechanism contributing to energy homeostasis. [NPID: perception, homeostatic feeding, hedonic feeding, food pleasure, feeding behavior, reward]

This 2011 study assessed the impacts of sensory specific satiety (SSS) and sensory specific desire to eat (general wanting for certain taste categories) on the subsequent food choices of children and adults. The 87 children and 49 adults who participated in this study were fed sweet pear banana yoghurt until satiation (fullness) and were tested on foods representing sweet, salty, sour, bitter, "fatty", and "spicy" flavors too. The hunger, satiation (state of fullness), liking, and wanting for the test foods and the yoghurt were reported at baseline and after meal consumption. Sensory specific satiety and sensory specific desire were expressed differently in children and adults. The children’s sensory specific satiety was bound to the yoghurt, whereas a transfer in SSS was observed in adults to the uneaten foods sharing sensory characteristics with the yoghurt (namely sweet, sour and "fatty"), reducing their liking after intake. The same trend was seen for sensory specific desire to eat. These variations in expression of SSS and SSD between adults and children may have major implications for the planning of meal compositions. [NPID: perception, sensory specific satiety, desire to eat, meal planning, portion control]