Diet and Sensory-Perception

This 2016 article explores the impact of the increasing exposure in society to images of desirable foods (what is often labelled 'food porn', or 'gastroporn') via digital interfaces might have, and whether it may inadvertently be exacerbating our desire for food (what we call 'visual hunger'). Here Spence et. al (2016) review the evidence for the potential profound effect viewing these images may have on neural activity, physiological and psychological responses and visual attention (especially in the ‘hungry’ brain). It is explained that the blame is often put on the global food companies for offering addictive foods, designed to use just the right amount of pleasurable ingredients such as sugar, salt, fat to hit the “bliss point” and for making these calorie-rich foods so accessible. The review aimed to find out if there are other implicit cues in our environments that might be triggering hunger more often than it is good for human well-being. [NPID: food porn, visual hunger, desire, craving, neural activity, bliss point, well-being, perception]

Sütterlin and Siegrist (2015) set up 4 experiments to find out whether people use simple heuristics to assess the healthiness of food products since for example the inclusion of the word “fruit” in “fruit sugar”, the colloquial name for fructose in Germany could mislead one to perceive the product as relatively healthy due to the association between fruit and health. Experiment 1 involved providing 164 individuals with one of two cereal bars, with one group given the nutrition table with the label “fruit sugar” and the other group provided with that labeled solely “sugar”. The results pointed to the participants holding a more positive perception of the “fruit sugar” cereal than the bars excluding the word “fruit”. Experiment 2 was a within-subjects designed version of Experiment 1, with all 202 subjects evaluating both cereal bars simultaneously, which resulted in the same trend occurring. Experiment 3 (N = 251) ruled out the alternative explanation that the effect could be due to differing inferences about the product's ingredients based on the label used, that is, that the product labeled with "fruit sugar" contains fruit. Results from the 4th experiment involving 162 participants indicated the labeling of the word “sugar” and its healthiness association mediated the previously observed effect. This study clarifies that symbolic information on food products can influence people’s perception of its healthiness, which can prove valuable from a marketing and public health standpoint. [NPID: perception, wording, positive perception, labels, sugar, marketing, public health]

This review seeks to find the impact of cognitive features on the perceived healthiness of foods and the resulting influence on overall food choices and consumption. It is suggested the inclusion of nutritional information on products in the form of labels and claims, which was integrated as a strategy to promote healthy diet consumption, could be misinterpreted by the consumers. The findings of this review imply cognitive factors (including type of food and branding) may not consistently or systematically affect food choice and intake but significantly contributes to judgmental bias and can influence the person’s perception of healthiness. [NPID: perception, food choice, decision-making, cognition, branding, judgmental bias]

Harray et. al (2017) compared the perceived and actual intakes of energy-rich nutrient-poor ‘junk food’ (JF) and sugar-sweetened beverages (SSB) in young adults in Perth of Australia, by assessing before-and-after eating images of the standardised portions (143kcal) of JF and SSB. Amongst the adult participants (aged 18-30), mean consumption of JF+SSB was 3.7 (2.0) servings per day. The women who thought about drinking less SSB were found to consume more servings per day (1.5 (1.2)) than men who thought about drinking less (0.7 (0.5)). On the other hand, men who planned to cut down on JF ate more servings/day (4.6 (2.4)) than women who wanted to reduce JF intake (2.5 (0.7) servings). Those who consumed the least JF and SSB were individuals who paid a lot of attention to include healthy choices into their diet, who consumed significantly less than those who took only a bit of notice, were not thinking much about it and those who didn’t consider health at all in their food intake. These results suggest perceptions and attitudes regarding JF and SSB can be associated with level of consumption. Since those individuals who did not consider cutting down on these foods consumed larger amounts, they appear to be an important target group for promoting healthy eating. [NPID: perception, junk food, sugar-sweetened beverages, Australia, portion control, attitude]

Since there is evidence indicating the potential approach oriented towards eating pleasure to promote the consumption of healthy foods, Vaillancourt et. al (2019) compared perceptions and the potential effect of pleasure-oriented as well as health-oriented messages on promoting healthy eating among French-Canadians. Perceived message orientation and effectiveness, perceptions towards healthy eating as well as emotions, attitude towards healthy eating, and intention to eat healthily were evaluated. The study population - consisting of 100 adults with an average age of 45.1, 50:50 male to female ratio - were randomly assigned to read one of the two leaflets with the messages, before completing questionnaires online and also reporting their experiences in a visit to the Institute of Nutrition and Functional Foods. Both pleasure and health messages significantly improved global attitude towards healthy eating while perceived message effectiveness and induced emotions in response to reading were similar between the two leaflets. The pleasure-oriented message was successful in inducing the perception that eating healthy can be pleasurable, with additional analyses also revealing the pleasure leaflet increased affective attitude towards healthy eating to a greater extent than the health leaflet. The health message appeared to improve cognitive attitude more than the pleasure leaflet however. The researchers conclude that the leaflets may be appropriate to promote healthy eating through health- and pleasure-related approaches. [NPID: perception, eating pleasure, French-Canadians, marketing, promotion, affective attitude, affect]

In this qualitative study published in 2018 16 key informant interviews were conducted and eight focus group discussions took place in northern Ethiopia in order to find out people’s perception of a ‘healthy’ diet in this African country and the barriers to practice this idea of a ‘healthy’ diet. The Ethiopians’ practice was mostly consistent with their perception, while they sometimes acted contrary to the perception because of personal preference and physical or financial obstacles. People were often unconcerned by the health implications of their habitual dietary practice, such as drinking a lot of sweet coffee. This study investigated and has shown the dynamics between perception and practice of ‘healthy’ diets among people in northern Ethiopia with the aim of removing any obstacles to a beneficial diet and raising awareness in the country of non-communicable diseases (NCDs) such as cardiovascular disease and diabetes, which are increasing with regards to burden in these low-income countries. [NPID: perception, Ethiopia, physical obstacles, financial obstacles, mone, awareness, obstacles, cardiovascular disease, diabetes, low-income countries]

This 2015 study conducted focus groups with Brazilian university students to find out their perceptions of the concept of calories, how it relates to food healthiness, and the role of calorie information on menus in influencing food choices in different restaurant settings. Among the 21 undergraduate students who took part in this cohort, calories were understood to be energy units and their excessive intake was associated with weight/fat gain. However, food healthiness was not associated with calorie content, but rather with food composition as a whole. Calorie information on restaurant menus was not considered enough to influence food choice, with only some participants also using calorie information on menus to control food intake or body weight. The discussions between the students suggested their comprehension of healthy eating is a more complex issue than calorie counting, and they would need more information on nutrition, not only about calorie content, in order to influence food choices in restaurants. [NPID: perception, calories, food choice, decision making, weight gain, calorie content, nutrition]

With the aim of improving the effectiveness of nutrition education programs and behavior change campaigns, Pettigrew, Talati and Pratt (2017) studied 409 Australian survey respondents aged 25-64 years on their perceptions of the meaning of four terms used to describe unhealthy foods: junk food, snack food, party food and discretionary food. The research found ‘junk food’ to be the term most aligned with unhealthiness, and likely to represent wording that is relevant to many target audience members. Other findings included the term “discretionary food” was not a familiar term for many respondents, and snack foods were considered to include both healthy and unhealthy food products. Both snack foods and party foods were often described as being consumed in small portions. These results highlighted that different terms for unhealthy foods can have substantially varying meanings for audience members and therefore, a detailed understanding of these meanings is required to ensure that nutrition guidance and health promotion campaigns use appropriate terminology. [NPID: perception, nutrition education programs, behavior change campaigns, junk food, snack food, party food, wording, target audience, marketing, terminology]

König & Renner (2019) conducted three studies with intervention strategies for boosting healthy food choice by prompting consumers to eat a colourful lunch at the appropriate moment. Effectivity and feasibility of this intervention strategy were tested in two laboratory experiments and one real-life, smartphone-based Ecological Momentary Intervention. The first study with 83 participants involved 4 meals (colourful, typical, healthy and low-calorie), the second with 42 subjects and tested 3 meals (colourful, typical and varied) from a Fake Food Buffet, and in study 3, 80 participants recorded images of 1,210 lunch meals over a period of 3 weeks using mobile visual food recording. All participants were asked to rate the prompts’ feasibility and in the second week, received a daily smartphone prompt to eat a colourful lunch. Results showed that prompting the sample to eat colourful foods increased the proportion of healthy foods consumed compared to typical meals in all three studies, with the individuals taking part in the study reporting that the prompt was easy to follow and act upon. In studies 1 and 2, colourful meals contained more fruit and vegetables, while in study 3 the prompt increased vegetable consumption. The colourful meals were said to be the tastiest in study one. This study suggests it may be promising to prompt people to eat colourful meals to encourage healthy food choices in daily life. [NPID: perception, fruit and vegetable intake, food color]

While energy-containing drinks are said to have a minor effect on satiety (sensation of feeling full), McCrickerd et al. (2014) assessed whether the context in which lower- (LE, 75 kcal) and higher-energy (HE, 272 kcal) beverages are consumed can influence the level of satiety it induces. The two beverages were consumed by 80 participants over two test days in one of four contexts: 20 individuals drank the thin version of the test-drink as a thirst-quencher; another 20 people consumed the beverage as a filling snack; 20 more participants drank the beverage after being given no additional information; and a fourth group of 20 received subtly thicker versions of the beverages without additional information. The amount of food eaten at lunch one hour later depended on the beverage context and energy content (p = 0.03). No significant differences in consumption were found between the higher- and lower- energy drinks in the participants who were not given additional information and in the individuals who perceived the drinks as just thirst-quenchers. But when the beverage was consumed as a filling snack, the subjects ate less at lunch after the HE beverage compared to the LE version. This effect was also observed among those who drank subtly thicker beverages - food consumption was lower after the higher-energy test-drink. These findings provide evidence that beverage intake can affect the impact of its nutrients on appetite regulation and that a beverage's sensory characteristics can limit its satiating power. [NPID: perception, satiety, fullness, energy content, drinks, beverage, sensory-perception]

While slow and prolonged food consumption is believed to make you feel more full, this 2018 review assessed the impact of oral processing characteristics (for example chewing and lubrication) on food intake and measures of appetite such as hunger and desire to eat. The systematic literature search on 6 different databases yielded 38 papers (detailing 40 unique studies with 70 subgroups), which were used for meta-analysis. Raw data on food intake was seen 65 times, hunger 22 times, and desire to eat ratings 15 times. Oral processing parameters such as number of chews, eating rate and texture manipulation seemed to substantially affect food consumption and appetite ratings to a lesser extent. Meta-analysis also indicated that aspects of oral processing related to chewing elicited a significant effect on self-reported hunger and food intake. Krop et al. (2020) insist that future research should confirm the role of oral processing including chewing and lubrication in promoting satiety, especially since few studies have reported the impact of lubrication on appetite. [NPID: perception, satiety, fullness, oral processing, chewing, appetite lubrication]

While food preferences and dietary habits are heavily influenced by taste perception, Chamoun et al. (2018) point out that characterization of taste preferences based on genetic variation is rising. Taste biology and genetics may lead the way to novel strategies and thereby the reduction/prevention of chronic diseases. This review focuses on single nucleotide polymorphisms (SNPs), which are specific genetic variations that, if occur in taste receptors, have been associated with the way in which fat, sweet, bitter, umami, and salt tastes are experienced. Also discussed are how these SNPs contribute to food preferences and chronic disease/health. The authors highlight the growing evidence that suggests that the role of genetics in taste perception may be more important and influential in children than adults due to the significant differences in cultural knowledge and awareness. [NPID: perception, taste perception, genetic variation, chronic disease, nucleotide polymorphisms, preferences, cultural factors, cultural influences]

Tan & Tucker (2019) conducted a systematic review of studies examining the relationship between taste function/perception and dietary consumption, in order to find the measure of taste most closely associated with dietary intake in healthy adults. Studies were grouped into 3 categories: those that assessed taste sensitivity; taste intensity; and hedonic (pleasure-related) responses to sweet stimuli. While there was little evidence linking sensitivity and intensity with dietary intake measures, hedonic studies were more likely to show associations with dietary consumption, particularly when analyzing participants who like sweetness separately from those who dislike sweet foods. However, the heterogeneity (diversity) among the dietary measures and stimulus concentration of these studies, as well as the small sample sizes, likely made it difficult to determine consistent relationships between the variables. [NPID: perception, taste function, taste perception, taste sensitivity, hedonic, diet diversity]

Low et al. (2014) explain that taste may play an important role in influencing food acceptance and/or energy intake since a person’s ability to detect or sense sweetness in the oral cavity is thought to be one of many factors involved in determining food acceptance. In addition, evidence is emerging suggesting that the signaling mechanisms related to sweet tasting may be working in the gastrointestinal system as well as in the oral cavity. To explain the excess energy intake thought to be substantially contributing to the growing global rate of obesity, a better understanding of the sweet taste system’s role is essential, not to mention greater knowledge on the individual variation in detecting sweetness in both the oral and gastrointestinal system. This review summarizes data potentially linking the sweet taste mechanisms within the oral cavity, gastrointestinal tract and the brain systems (activated by caloric sugar, high intensity sweeteners and sweet tastes) with satiation (sensation of feeling full) and thereby perhaps with BMI and obesity. [NPID: perception, food acceptance, taste perception, sweet taste perception, obesity, oral system, gastrointestinal system, satiation]

Spence (2015) explains how the sounds that you hear when consuming foods and drinks are critical to your experience and enjoyment. This can be the sound made by chewing and biting, while the texture of the food may also be important. Just listen to those crispy, crunchy and crackling noises. It is the synchronization of such eating sounds with the act of feeding that can alter the consumer’s experience of what they think they are eating, according to a rising number of studies. [NPID: perception, sound, hearing, chewing, biting, texture, crispy, crunching, cracking]

Since food appearance, particularly its colour, influences flavor perception, this 2020 study utilized the power of virtual-reality (VR) technology to assess whether changing the milkiness of coffee through VR can affect perceived flavor and liking. Thirty-two UK consumers were given four samples of black cold brew coffee at 4% and 8% sugar concentration while wearing VR headsets and viewing coffee manipulated to look a dark brown or light brown colour. Each participant tasted each sweetness and color combination before rating the sweetness, creaminess, and liking for each beverage sample. The results showed that drink color did not have an impact on the subjects’ perceived sweetness or liking. However, perceived creaminess was found to be significantly altered by the color of the drink. The light brown coffee was rated to be creamier than the dark brown sample. Overall, the researchers recommend the utilization of VR in the examination of food perception. A future prospect with potential for VR would be promoting healthy dietary behaviors through food appearance manipulation. [NPID: perception, flavor perception, VR, virtual reality]

While hedonic pleasure has been linked with brain function in the past, Berridge & Kringelbach (2011) explore new insights into how brains contribute to the hedonic aspect of sustained or frequent pleasure. Well-being and happiness have been reported to require both positive affect or pleasure (hedonia) and a sense of meaningfulness or engagement in life. This article also discusses how the brain might connect these two to form states of positive well-being. There has been recent advancements in the understanding of hedonic processing due to the largely similar hedonic brain mechanisms seen in humans and other mammals. It has been reported that the brain mechanisms of higher abstract pleasures strongly overlap with more basic sensory pleasures. Thus, the strategy of Berridge & Kringelbach acknowledges this new evidence as well as the findings on brain mediators that produce the pleasure of sensations. [NPID: perception, hedonic, pleasure, well-being, happiness, hedonia, sensory pleasure]

While the senses taste and smell play an influential role in the choice and intake of food, this 2017 article discusses the differences in functions of smell and taste on dietary behavior. Boesveldt & de Graaf explain that sensing an odor leads to greater appetite for the cued food but its impact on food choice and consumption is a little less clear - perhaps involving other factors such as awareness or intensity of the odors, and the personality traits of the person. On the other hand, the role of taste is better understood. In addition to texture, taste is responsible for determining the rate of food intake, the exposure duration of food in the mouth, and thus level of satiation. By applying these findings to real-life situations, the longer-term impacts of taste and smell on energy consumption can be analyzed. And in doing this, hopefully people’s eating behaviors can be modified to move towards a less obesogenic society. [NPID: perception, taste, smell, dietary behavior, texture, rate of food intake, obesity]

In this 1998 study designed to assess how oral, gastric, and intestinal factors contribute to appetite control, 425ml of tomato soup was administered to nine healthy, fasted, male volunteers in various forms. Soup was given orally, through the stomach intubation (intragastrically - covertly and overtly), and through the duodenum (intraduodenal - overtly). The subjects rated their levels of fullness, hunger, and desire to eat over a 2-hour period, while the rate of gastric emptying was also measured after oral and intragastric soup intake. After soup was infused into the small intestine at a rate in line with normal gastric emptying, there was no significant impact on hunger, desire to eat, or fullness ratings. Also, there was no variation in gastric emptying between covert and overt intragastric soup infusions, but the researchers highlighted a suppression of appetite following covert intragastric administration that was also heightened when participants were informed of the route of infusion. Between all conditions, oral consumption resulted in the greatest appetite inhibition, and produced a slower rate of gastric emptying compared with both methods of intragastric soup infusions. Cecil et al. also reported strong associations between appetite ratings and both gastric and intestinal contents following intragastric soup intake, and these were found to be stronger after oral soup consumption. It was clear that orosensory, gastric and intestinal factors can interact to produce optimal expression of fullness and hunger suppression. [NPID: perception, appetite control, stomach intubation, desire, craving, hunger suppression, satiety, fullness]

This 2015 article emphasizes the influences of various food properties on several outcomes. Food form in particular can impact nutritional outcomes through multiple mechanisms involving cognitive and oral sensory processes, and stomach and intestine activity. Dhillon et al. explain that holding expectations about the form of food can determine digestive processes, metabolism occurring after absorption, the sensory ratings of the food product, and the level of fullness one feels. Moreover, mastication depends on the structure of food, which can alter appetite, energy, and the nutrient bioavailability in the digestive tract. Finally, the physical form of food particles can affect absorption of nutrients, the speed at which the stomach is able to empty its contents, and the time it takes for the food to pass through the intestine also. Thus, there are significant implications involving food form in ingestive behavior and health outcomes. [NPID: perception, cognition, oral sensory processes, digestion, metabolism, fullness, satiety, nutrient absorption, ingestive behavior]

Since food assessment varies across cultures, Duerland et al. (2020) conducted a study to compare the sensations experienced following food ingestion by participants in China (n=53) and those in Denmark (n=48). The main objective was to discover the drivers of post-ingestive food pleasure (PIFP) among both sets of subjects. Both post-ingestion sensations and PIFP were measured for 3 hours following breakfast consumption. Importantly, perceived satisfaction, in addition to physical, mental, and overall well-being were highly impactful on PIFP in both countries. However, there were differences between the two groups of subjects. Unlike the Chinese, the Danish consumers perceived sensations such as satiety, hunger, desire to eat, and “in-need-of-food” to be influential on PIFP. On the other hand, PIFP was reported to be driven by vitality-related sensations such as energized, relaxation, and concentration. This study suggests that there are similarities and also distinct differences in the cultural constructs of post-ingestive food pleasure in Denmark and in China. [NPID: perception, food assessment, cultural differences, culture, China, Denmark, post-ingestive food pleasure, breakfast consumption, cultural constructs]

This 2016 study tested the relationship between the level of food processing involved in making a product and people’s glycemic and satiety responses. The food served varied in terms of processing based on the international NOVA classification, which were: raw and minimally processed foods; processed foods; and ultra-processed foods (industrial products made from substances extracted/derived from food additives). Fardet hypothesized that there would be a correlation between the extent to which the product was processed with the satiety index and glycemic response. Glycemic response was assessed based on the glycemic index (GI) and the glycemic glucose equivalent (GGE), a new index that calculates the quantity of glucose needed to induce the same volume of change in the blood glucose concentrations that were observed following intake of the test food. Strong associations were identified between glycemic glucose equivalent (the new index), satiety index, and the level of food processing, while the glycemic index was not found to correlate with degree of food processing. The data suggested that the more processed the food product is, the greater the glycemic response and the lower its potential to achieve satiety. The results are in support of the advice to consume complex and natural, and even minimally and/or processed foods rather than ultra-processed foods if one is searching for weakly hyperglycemic and satiating foods. [NPID: perception, food processing, glycemic, satiety, processed food, food additives, glycemic index]

In the first of two crossover studies conducted by Duszka et al. (2020), the participants were shown random non-food related pictures on the first day and food related photos on the second day. Following the picture-viewing session (as part of the second study) the subjects were asked to drink milkshake and have their glucose, triglycerides and several hormone levels checked. The study found that regulation of total ghrelin concentration following food stimulation (through seeing food pictures) is highly individual. Responders had higher ghrelin levels, while the concentrations decreased following a meal. In addition, the color intensity and protein content of the foods displayed in the pictures were negatively associated with individual ratings of the pictures. The researchers suggest that the protein content of foods and green color intensity of pictures have an impact on the attractiveness of the food/meal. It was also concluded that the concentrations of several appetite-related hormones are disturbed by the viewing of food pictures. This connection between visual cues and physiological response is likely to be clinically relevant. [NPID: perception, glucose, triglycerides, hormones, protein, food color]

In this 2019 crossover trial, 20 weight-stable adults were admitted to a clinic and randomized to receive either ultra-processed or unprocessed diets for 2 weeks, followed immediately by the alternate diet for another 2 weeks. The subjects were given unrestricted access to each meal, which were designed to be matched in terms of calories, energy density, macronutrients, sugar, sodium, and fiber. The research found that energy consumption was significantly greater when participants were on ultra-processed diets, compared to when eating unprocessed meals. Intakes of carbohydrates and fats were higher while on ultra-processed meals, but protein consumption was not greater. Furthermore, weight gains of 0.9 ± 0.3 kg were observed during the ultra-processed diet, while the unprocessed diets were associated with weight loss of 0.9 ± 0.3 kg (both statistically significant). Weight changes were highly correlated with energy intake. This data suggests that limited eating of ultra-processed foods could be an effective strategy for weight control and obesity management. [NPID: perception, processed foods, carbs, fat, protein, weight control, obesity]

Hermann et al. (2019) writes that while the measuring of food cue reactivity through functional magnetic resonance imaging (fMRI) can help determine people with dysregulated reward brain systems and increased susceptibility to environmental cues that tend to cause obesity, weight loss interventions have more recently been shown to possibly influence fMRI food cue reactivity. This is why this present study assessed whether fMRI food cue reactivity could be used to predict diet-induced early changes in neural processing in the striatum region of the brain that can indicate the outcome of the weight loss intervention. This study examined the food cue reactivity of the participants one month after the start of the weight loss program, as well as their relationship with weight changes observed at the end of the six-month intervention. A significant association was found between BMI changes after the six months with early transformations in fMRI food cue reactivity in the striatum. This study has provided evidence of the diet-induced early alterations in fMRI food cue reactivity in the striatum that can predict the outcome of weight loss interventions. [NPID: perception, reward, dysregulation, environmental cues, obesity, weight loss interventions, striatum, weight loss]

In this 2012 study, the main meal recipes created by television chefs were assessed and compared with ready meals sold by supermarkets on energy and macronutrient content, and also on their adherence to nutritional guidelines. Howard et al. analyzed 100 recipes from the five best-selling cookery books by UK television chefs and 100 own brand ready meals from the three leading UK supermarkets. The outcome measures included the number of meals for which the nutritional content complied with recommendations published by the World Health Organization (WHO), and the proportion of nutrients classed as either red, amber, or green according to the UK FSA’s “traffic light” system for labelling food. The study found that although none of the recipes nor ready meals complied with the WHO recommendations, the ready meals were more likely to comply with the recommended percentage of energy obtained from carbohydrates, sugars, and fiber density (all p ≤ 0.05). The chefs’ recipes had a greater chance of complying with the recommended quantity of sodium, but the author notes that salt used for seasoning was not included in the assessment. The most common traffic light color under the FSA’s food labelling recommendations was red for the recipes (47%) and green for the ready meals (42%). Moreover, the recipes were made up of significantly more energy, protein, fat, and saturated fat per portion than the ready meals. [NPID: perception, nutritional guidelines, television chefs, food labeling, food labels, salt, ready meals, saturated fat]

The objective of this 2012 study was to examine whether the impact of olfactory (relating to sense of smell) food cue exposure on young women’s food intake is moderated by the duration of the cue exposure and trait impulsivity. This study was designed as a 2x2 between-participants trial, meaning that each subject would experience 4 conditions varying in food cue exposure (baked cookie smell or no smell) and duration of cue exposure (short- or long- term). The 109 normal-weight women who took part were assessed on food consumption during a bogus taste-test, and tested on several saliva measures during the cue encounter. The results demonstrated that low-impulsive females ate more food when faced with an olfactory food cue, whereas no significant difference was detected among the high-impulsive women who experienced the same food cue. The evidence indicated that the subjects’ food consumption were not influenced by the duration of the cue exposure, but moderated by impulsivity, and not by saliva flow. Larsen et al. state that the findings may be explained by the lack of instructions communicated to the women to focus on the food cue. The research ultimately uncovered that individuals who are normally well-controlled are susceptible to the power of less explicit olfactory food cues. [NPID: perception, olfactory, food cue, trait impulsivity, food odor, impulsivity]

Since higher food viscosity leads to longer stimulation of the oral senses, Mars et al. set out to study the metabolic responses associated with these sensory signals that are firing during consumption. This study specifically looked at the impact of food viscosity on people’s learned satiation (feeling of fullness). To begin, the participants were split into 2 intervention groups: one that was offered unlimited access to a low viscosity (LV) yoghurt for breakfast; while the other group received as much high as they wanted of a viscosity (HV) yoghurt. Later, in the 4-week learning period, the subjects had an unlimited supply of either a high energy density (HED) yoghurt or a low energy density (LED) yoghurt, while being exposed to each yoghurt 10 times a day on alternate days. There was a significant link found between exposure and energy density among the high-viscosity intervention group. For example, 46+/-16 g more of the low energy density yoghurt was eaten after 10 exposures, compared with the high energy density yoghurt. However, there was no notable relationship between exposure and yoghurt energy density in the low-viscosity intervention group. These results seem to suggest that higher viscosity foods support learned satiation. [NPID: perception, food viscosity, viscosity, oral senses, satiety, fullness]

While sensory food cues have been shown to stimulate the secretion of saliva, Morquecho-Campos et al. (2019) wanted the effects of changing food odors and olfactory (smell-related) stimulation on saliva secretion and composition, respectively. In the first study, 36 individuals were randomly exposed to no-odor, non-food, and odors that are perceived as sweet, savory, and sour taste. While the second study involved 60 participants who were randomly tested with no-odor, non-food, and odors signaling carbohydrates, protein, fat, and low-calorie food. Their whole-mouth saliva was collected and assessed for secretion rate, subjective salivation, visco-elasticity, mucin concentration, α-amylase and lingual lipase activity. Both studies provided evidence that food odors significantly increased saliva secretion rate compared to no-odor and non-food conditions. However, there were no apparent differences in salivary composition. Nevertheless, this data reveals that food odors can greatly influence anticipatory saliva responses and therefore can alter dietary behavior. While sensory food cues have been shown to stimulate the secretion of saliva, Morquecho-Campos et al. (2019) wanted the effects of changing food odors and olfactory (smell-related) stimulation on saliva secretion and composition, respectively. In the first study, 36 individuals were randomly exposed to no-odor, non-food, and odors that are perceived as sweet, savory, and sour taste. While the second study involved 60 participants who were randomly tested with no-odor, non-food, and odors signaling carbohydrates, protein, fat, and low-calorie food. Their whole-mouth saliva was collected and assessed for secretion rate, subjective salivation, visco-elasticity, mucin concentration, α-amylase and lingual lipase activity. Both studies provided evidence that food odors significantly increased saliva secretion rate compared to no-odor and non-food conditions. However, there were no apparent differences in salivary composition. Nevertheless, this data reveals that food odors can greatly influence anticipatory saliva responses and therefore can alter dietary behavior.

While we know that the sensory properties of foods largely determine palatability, the aim of this 2012 study was to find out how these sensory properties can influence how much we eat. The 40 participants were female and classified on their sensory sensitivity (high/low) using scores on the Adult Sensory Profile (a measure of sensory processing). After measuring their chocolate intakes during the experiment, it was discovered that the high-sensitivity individuals ate significantly more than the low-sensitivity subjects. There was a positive correlation between sensory sensitivity scores with emotional eating. These results suggest that people with higher sensitivity to sensory properties of food are more likely to consume greater amounts of food due to the heightened perception of palatability. [NPID: perception, palatability, sensory properties, emotional eating]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

The effect of item placement on snack food choices from physical and online menus