Oral fat perception is related with body mass index, preference and consumption of high-fat foods

A new perspective on obesity: perception of fat taste and its relationship with obesity

Background: Obesity, which results from a long-term positive energy balance, is affected by many factors, especially nutrition. The sensory properties of foods are associated with increased food intake through hedonic appetite. Taste perception, a component of flavor, is also responsible for increased consumption, through reward and hedonic mechanisms. Foods with high fat and energy content are among the foods that create the reward perception. The perception of fat taste, the primary taste that has recently entered the literature, may also be associated with increased food consumption and body weight. Therefore, in this review, the relationship between fat taste and obesity is examined, using the latest literature.

RESULTS

Different hypotheses have been proposed regarding the mechanism of the relationship between fat-taste perception and obesity, such as hedonic appetite, microbiota, decreased taste perception, and increased taste threshold level. In addition, some studies examining this relationship reported significant associations between the level of fat-taste perception and obesity, whereas others did not find a significant difference.

CONCLUSION

Considering the prevalence and contribution to obesity of Western-style nutrition, characterized by high amounts of fat and sugar consumption, elucidating this relationship may be an essential solution for preventing and treating obesity.

The gustin gene variation at rs2274333 and PROP taster status affect dietary fat perception: a stepwise multiple regression model study

Gustin, a trophic factor for taste bud development, and its polymorphism at rs2274333 influence taste perception of 6-n-propylthiouracil (PROP) and fungiform papillae (FP) density. The PROP taster status affects dietary fat sensing and body composition. However, there is a paucity of research on the gustin genotype with dietary fat perception, PROP tasting ability, and body mass index (BMI). Thus, taste sensitivity to fat and bitterness was evaluated in 178 healthy individuals. The general labeled magnitude scale was used to determine suprathreshold taste intensity ratings, whereas the alternative forced choice approach was used to estimate the taste-sensing ability. The FP density was assessed by applying blue-colored food dye over the anterior region of the tongue. Restriction fragment length polymorphism was used to detect the genetic polymorphism (rs2274333) in the carbonic anhydrase VI (CA-VI) gene. Fisher's chi-square analysis showed that the CA-VI genotype and allelic frequencies significantly correlated (p<0.001) with the PROP taster status and BMI. Healthy individuals with AA genotypes of the CA-VI polymorphism and PROP super-tasters demonstrated stronger gustatory sensitivity for linoleic acid (LA) with greater FP density in comparison to individuals with AG/GG genotypes and other PROP taster groups. Stepwise forward multiple regression analysis indicates that BMI and PROP taster status significantly influence the LA sensing ability. The suprathreshold intensity rating for LA was also significantly impacted by PROP taster status and CA-VI genotypes, with a variation of 73.3%. Overall, our findings show a relationship between the taste papillae environment and the CA-VI genetic mutation at rs2274333, which influenced the gustatory preference for dietary fat and bitter taste.

Evaluation of oral health, taste perception, nutritional status and emotional well-being in post-menopausal women

BACKGROUND

In postmenopausal women (PMW), vasomotor symptoms, emotional oscillations and sleep disturbances can affect physiological and psychological functioning. However, the effect of menopause on oral health-related parameters is not been thoroughly studied.

OBJECTIVE

To evaluate oral health, taste perception, eating habits, nutritional status and emotional well-being in PMW compared with a group of young and healthy pre-menopausal women (PrMW).

MATERIALS AND METHODS

Two groups (Group I: PMW and Group II: PrMW) with 30 participants each, participated in the cross-sectional study. The study proforma contained measures of oral health, taste perception, nutritional status and anxiety levels of the women in both groups using validated and previously used tools were designed and implemented. The data were analysed with student t, Mann-Whitney U, and chi-squared tests to evaluate the differences between the two groups.

RESULTS

The cross-sectional study indicates no major differences in oral health, taste perception, nutritional and emotional status between PMW and PrMW. Nonetheless, there was a significant difference in perception of 'front teeth lengthening in size' and change in hot and cold sensations between the groups. Furthermore, the study group with PMW tends to have fewer natural teeth than the reference group.

CONCLUSION

Overall, menopause does not appear to affect oral health, taste perception, nutrition or emotional health. It is suggested that oral health and taste perception, as well as nutritional and emotional status, are associated with gradual aging processes that may or may not be affected by menopause.

Long-term regulation of fat sensing in rainbow trout (Oncorhynchus mykiss) fed a vegetable diet from the first feeding: focus on free fatty acid receptors and their signalling

Taste plays a fundamental role in an animal’s ability to detect nutrients and transmits key dietary information to the brain, which is crucial for its growth and survival. Providing alternative terrestrial ingredients early in feeding influences the growth of rainbow trout (RT, Oncorhynchus mykiss). Thus, the present study aimed to assess the influence, via long-term feeding (from the first feeding to 8 months), of alternative plant ingredients (V diet for vegetable diet v. C diet for a control diet) in RT on the mechanism of fat sensing at the gustatory level. After the feeding trial, we studied the pathways of the fat-sensing mechanism in tongue tissue and the integrated response in the brain. To this end, we analysed the expression pattern of free fatty acid receptors (ffar) 1 and 2, markers of calcium-signalling pathways (phospholipase Cβ, Orai, Stim or Serca), the serotonin level (a key neurotransmitter in taste buds) and the expression pattern of appetite-regulating neuropeptides in the hypothalamus (central area of appetite regulation). The results revealed that the V diet modified the expression pattern of ffar1 and paralogs of ffar2 genes in tongue tissue, along with differential regulation of calcium-signalling pathways and a defect in serotonin level and brain turnover, without influencing neuropeptide expression. This study is the first to support that changes in feeding behaviour of RT fed a V diet could be due to the difference in nutrient sensing and a decrease in hedonic sensation. We revealed that RT have similar fat-detection mechanisms as mammals.

Adiponectin Enhances Fatty Acid Signaling in Human Taste Cells by Increasing Surface Expression of CD36

Adiponectin, a key metabolic hormone, is secreted into the circulation by fat cells where it enhances insulin sensitivity and stimulates glucose and fatty acid metabolism. Adiponectin receptors are highly expressed in the taste system; however, their effects and mechanisms of action in the modulation of gustatory function remain unclear. We utilized an immortalized human fungiform taste cell line (HuFF) to investigate the effect of AdipoRon, an adiponectin receptor agonist, on fatty acid-induced calcium responses. We showed that the fat taste receptors (CD36 and GPR120) and taste signaling molecules (Gα-gust, PLCβ2, and TRPM5) were expressed in HuFF cells. Calcium imaging studies showed that linoleic acid induced a dose-dependent calcium response in HuFF cells, and it was significantly reduced by the antagonists of CD36, GPR120, PLCβ2, and TRPM5. AdipoRon administration enhanced HuFF cell responses to fatty acids but not to a mixture of sweet, bitter, and umami tastants. This enhancement was inhibited by an irreversible CD36 antagonist and by an AMPK inhibitor but was not affected by a GPR120 antagonist. AdipoRon increased the phosphorylation of AMPK and the translocation of CD36 to the cell surface, which was eliminated by blocking AMPK. These results indicate that AdipoRon acts to increase cell surface CD36 in HuFF cells to selectively enhance their responses to fatty acids. This, in turn, is consistent with the ability of adiponectin receptor activity to alter taste cues associated with dietary fat intake.

Taste but not smell sensitivities are linked to dietary macronutrient composition

Macronutrient intake and composition of diets (i.e., carbohydrate, protein, and fat) can vary substantially across individuals. Chemosensory functions are hypothesised to play a key role in modulating nutrient choices and intake. The present study tests links between individual gustatory or olfactory supra-threshold sensitivities and dietary macronutrient intake. A total of 98 European males (N = 81 for final analyses; age: 20-40 yo; BMI: 18.9-48.1 kg∙m^-2) were tested for supra-threshold sensitivities (d') to 3-gustatory (i.e., Sucrose, MSG, Dairy fat) and 3-olfactory stimuli (i.e., Vanillin, Methional, Maltol/Furaneol), followed by a 4-day weighed Food Record to give measures of macronutrient intake (kJ) and composition (%). With multivariate analyses (i.e., K-mean clustering, PCA, and Hierarchical Regression), gustatory and olfactory d' were compared across groups of individuals with distinct macronutrient composition or intake. Significant differences in gustatory d' were found across the clusters based on macronutrient composition (p < 0.05), but not for clusters based on intake. Hierarchical regressions suggested that gustatory d' played a significant role in predicting dietary carbohydrate composition and intake, with one-unit d' increase predicting reduction of 3%-4.66% (R² = 0.21, F_(5,75) = 5.38, p = 0.001). Moreover, every one-unit increase in d' to MSG increased protein composition by 3.45% (R² = 0.10, F_(5,75) = 2.83, p = 0.022) and intake by 392 kJ (R² = 0.08, F_(5,75) = 2.41, p = 0.044). By contrast, olfactory d' showed little association to macronutrient composition or intake (p > 0.05). Overall, we present intriguing new evidence that gustatory, but not olfactory, sensitivities are linked to dietary macronutrient composition, with relatively little effect on actual intake. These findings highlight possible action of a sensory-mediated mechanism guiding food choices.

The importance of the taste preferences and sensitivity of mothers and their children in the aspect of excessive body weight of children

INTRODUCTION

Food selection among adults and mostly children depends mainly on the taste of a dish. Poor taste sensitivity as well as strong preferences for sweet and fat taste may be the factors predisposing children to become overweight and/or develop obesity. Family environment, including mothers' eating habits and preferences, may affect children's taste perception and preferences. The aim of the study was to assess taste perception and preferences in children and their mothers in relation to their weight status.

METHODS

Sensory tests were carried out using puddings with different sugar and fat content. In all study participants anthropometric measurements (weight and height with BMI calculation) were performed.

RESULTS

The study results did not reveal any differences in the taste sensitivity of overweight/obese and normative body weight children. Similarity was found in the perception of different levels of sweet/fat flavors among children and parents. Overweight/obese children were two times more likely to choose a very fat and very sweet taste compared to normal weight children. The results showed that children prefer a sweet taste more often than their mothers. Mothers' fat taste preferences were important - the fatter the taste they selected, the greater the percentage of children with obesity.

DISCUSSION

Mothers' taste sensitivity may affect children's perception of the quality (intensity) of flavors. Normal-weight children chose a low fat and low sweet taste more frequently than those with excess of body weight. The role of parents in shaping taste preferences is of utmost importance and should be based on limiting the consumption of products rich in sugar and/or fat.

Explaining the effect on food selection of altering availability: two experimental studies on the role of relative preferences

BACKGROUND

Increasing the availability of healthier or plant-based foods increases their selection. The current studies aimed to examine the extent to which relative preferences account for food selections following availability interventions. In particular, (a) whether increasing the availability of lower-energy options increases the likelihood that individuals' highest-ranked option is lower-energy, and (b) the extent to which selections reflect individuals' highest-ranked option from the available range.

METHODS

UK adults (Study 1: n = 1976; Study 2: n = 1078) took part in within-subjects online studies. In both studies, the order of preference between food options was established by participants choosing the option that they would prefer "to eat right now" from every possible pairing within a pool of eight options. Then, participants were shown either predominantly higher-energy options (three higher- and one lower-energy) or predominantly lower-energy options (vice versa), presented in a random order.

RESULTS

When predominantly lower-energy options were presented, the odds of the highest-ranked option being a lower-energy option increased ten-fold (Study 1: odds ratio: 10.1; 95%CI: 8.9,11.4; Study 2: odds ratio: 10.4; 95%CI: 7.4,14.7), compared to when predominantly higher-energy options were available. In both studies, around 90% of selections reflected the highest-ranked option in the range offered in the studied availability conditions (range 88-92%).

CONCLUSIONS

These studies suggest that increased availability of lower-energy options increases the likelihood of an individual's highest-ranked option being lower-energy, and that the highest-ranked option has the greatest likelihood of selection. As such, preferences may be a key contributor to the effects of altering availability on food selections.

TRIAL REGISTRATION

ISRCTN ( http://www.isrctn.com/ISRCTN27598623 ; 3/12/19 [Study 1]; http://www.isrctn.com/ISRCTN61010183 ; 20/4/20 [Study 2]).

Effect of Beta 2-Adrenergic Receptor Gly16Arg Polymorphism on Taste Preferences in Healthy Young Japanese Adults

The Gly16Arg polymorphism results in a G to C nucleotide mutation in the human beta 2-adrenergic receptor (ADRB2) gene and has a relationship with obesity; however, this substitution’s effects on food preferences are unclear. Therefore, we determined this relationship among healthy young adults (mean age, 23.4; n = 52). To evaluate food preferences, four categories of food (sweet, salty, sour, and bitter) along with high-fat foods were evaluated using a self-reporting questionnaire. Male (n = 26) and female subjects (n = 26) were genotyped for the polymorphism and further divided into three groups (two homozygous groups, GG, CC; and a heterozygous group, GC). Preference for sour foods in the GG group was higher compared with that in the CC group in females (p < 0.05). When sweet foods were classified into low- and high-fat subgroups, preference for high-fat sweet foods in the GG group was higher than that for low-fat sweet foods in all subjects (p < 0.05). The degree of preference for high-fat foods in the GG group was higher than other groups for males (p < 0.05). These results suggest that ADRB2 polymorphism is associated with food preference. Understanding the relationship of ADRB2 substitution to food preference will be valuable for designing individualized anti-obesity strategies.

Taste of Fat and Obesity: Different Hypotheses and Our Point of View

Obesity results from a temporary or prolonged positive energy balance due to an alteration in the homeostatic feedback of energy balance. Food, with its discriminative and hedonic qualities, is a key element of reward-based energy intake. An alteration in the brain reward system for highly palatable energy-rich foods, comprised of fat and carbohydrates, could be one of the main factors involved in the development of obesity by increasing the attractiveness and consumption of fat-rich foods. This would induce, in turn, a decrease in the taste of fat. A better understanding of the altered reward system in obesity may open the door to a new era for the diagnosis, management and treatment of this disease.

The Association between Fat Taste Sensitivity, Eating Habits, and Metabolic Health in Menopausal Women

The aim of our study was to evaluate the associations between sensitivity to fat taste, eating habits and BMI value in a sample of menopausal Polish women. In a population of 95 women, fat taste thresholds with oleic acid were determined, allowing us to classify each woman as a hypersensitive or hyposensitive taster. Eating habits were assessed using a validated KomPAN questionnaire for food frequency. Dietary intake was evaluated based on a food diary. Selected biochemical parameters were measured using a Konelab20i biochemical analyzer. Anthropometric parameters and blood pressure were also measured. Twenty-two menopausal women were classified as hyposensitive to fat taste and 73 as hypersensitive. The hyposensitive tasters were significantly older (p = 0.006), with the majority of them (92%) being postmenopausal (p < 0.001); this group had significantly higher BMI values (p < 0.001) and other adiposity indicators compared to their hypersensitive counterparts. The hyposensitive tasters had higher blood pressure (systolic blood pressure; SBP p = 0.030; diastolic blood pressure; DBP p = 0.003), glucose (p = 0.011) and triacylglycerols levels than the hypersensitive tasters (p = 0.031). Almost half of them had diagnosed metabolic syndrome. Daily eating occasions were associated with low oral fatty acid sensitivity, irrespective of age (p = 0.041) and BMI value (p = 0.028). There were also significant associations between frequency of consumption of meats and eggs, as well as snacks and fast foods and low oral fatty acid sensitivity before adjustment for potential confounders (both associations p < 0.05), which remained after adjustment for age (both associations p < 0.05), but not after adjustment for BMI. A multivariate logistic regression analysis showed that higher BMI value (p = 0.003), along with postmenopausal status (p = 0.003), were associated with low fat taste sensitivity irrespective of age and consumed percentage energy from fat. Postmenopausal status and BMI are associated with low fat taste sensitivity. Fat hyposensitivity may also play a role in eating habits, leading to increased eating occasions and favoring certain types of food. These eating habits may determine increased body weight and the occurrence of metabolic syndrome in mid-life women, especially those who have undergone menopause and have been exposed to the physiological changes which are conducive to these relationships.

The association of fat preference with eating behavior and sex: Turkish version of the Fat Preference Questionnaire©

The fat content of food may play a role in food preferences. Increased fat intake has a role in elevated body weight. Firstly, we aimed to establish the Turkish version of the Fat Preference Questionnaire© and secondly to evaluate the relevant factors with dietary fat preference including body mass index (BMI); sex; and subscales of the Three-Factor Eating Questionnaire (TFEQ). The study was conducted with 261 participants among the academic staff of Yeditepe University. The Fat Preference Questionnaire© and TFEQ were applied. After the validity and reliability of the Turkish version of the Fat Preference Questionnaire©, Pearson's correlation coefficients were calculated to reveal the relationship between the scores of the Fat Preference Questionnaire©, BMI, and the four subscales of TFEQ. Weakly or moderately correlated variables were selected to perform two sets of hierarchical regression analyses. Turkish version of the Fat Preference Questionnaire© had statistically acceptable validity and reliability. Fat preference did not correlate with BMI (p > .05). Women showed a lower preference for high-fat foods and a higher dietary fat restriction (p < .05). The two subscales of TFEQ, the Disinhibition of Eating Control and the Susceptibility to Hunger, contributed to explain the variances in fat preference and dietary fat restriction (ΔR 2 = .04, p < .05). Fat preference correlates with Disinhibition of Eating Control and Susceptibility to Hunger, while fat restriction correlates only with Disinhibition of Eating Control although none correlates with BMI. Turkish version of the Fat Preference Questionnaire© is a valid instrument for further studies.

Ghrelin Receptors Enhance Fat Taste Responsiveness in Female Mice

Ghrelin is a major appetite-stimulating neuropeptide found in circulation. While its role in increasing food intake is well known, its role in affecting taste perception, if any, remains unclear. In this study, we investigated the role of the growth hormone secretagogue receptor's (GHS-R; a ghrelin receptor) activity in the peripheral taste system using feeding studies and conditioned taste aversion assays by comparing wild-type and GHS-R-knockout models. Using transgenic mice expressing enhanced green fluorescent protein (GFP), we demonstrated GHS-R expression in the taste system in relation phospholipase C ß2 isotype (PLCβ2; type II taste cell marker)- and glutamate decarboxylase type 67 (GAD67; type III taste cell marker)-expressing cells using immunohistochemistry. We observed high levels of co-localization between PLCβ2 and GHS-R within the taste system, while GHS-R rarely co-localized in GAD67-expressing cells. Additionally, following 6 weeks of 60% high-fat diet, female Ghsr^-/- mice exhibited reduced responsiveness to linoleic acid (LA) compared to their wild-type (WT) counterparts, while no such differences were observed in male Ghsr^-/- and WT mice. Overall, our results are consistent with the interpretation that ghrelin in the taste system is involved in the complex sensing and recognition of fat compounds. Ghrelin-GHS-R signaling may play a critical role in the recognition of fatty acids in female mice, and this differential regulation may contribute to their distinct ingestive behaviors.

Oral Signals of Short and Long Chain Fatty Acids: Parallel Taste Pathways to Identify Microbes and Triglycerides

Both short chain fatty acids (SCFAs) and long chain fatty acids (LCFAs) rely on free fatty acid receptors to signal their presence to the body, but their individual detection and putative reward systems are different. These separate, yet parallel, taste signaling pathways allow us to distinguish microbe-produced from triglyceride-based fatty acids. Free SCFAs indicate that the food has been fermented and may still contain living, probiotic microbes that can colonize the gut. Free LCFAs indicate the presence of calorie-rich triglycerides in foods. By contrast, LCFAs stimulate endocannabinoids, which reinforce overconsumption of triglycerides. Here we examine the separate oral detection and putative reward systems for both LCFA and SCFAs, and introduce a novel dietary LC:SC ratio as a guideline to improve metabolism and health.

Macronutrient Sensing in the Oral Cavity and Gastrointestinal Tract: Alimentary Tastes

There are numerous and diverse factors enabling the overconsumption of foods, with the sense of taste being one of these factors. There are four well established basic tastes: sweet, sour, salty, and bitter; all with perceptual independence, salience, and hedonic responses to encourage or discourage consumption. More recently, additional tastes have been added to the basic taste list including umami and fat, but they lack the perceptual independence and salience of the basics. There is also emerging evidence of taste responses to kokumi and carbohydrate. One interesting aspect is the link with the new and emerging tastes to macronutrients, with each macronutrient having two distinct perceptual qualities that, perhaps in combination, provide a holistic perception for each macronutrient: fat has fat taste and mouthfeel; protein has umami and kokumi; carbohydrate has sweet and carbohydrate tastes. These new tastes can be sensed in the oral cavity, but they have more influence post- than pre-ingestion. Umami, fat, kokumi, and carbohydrate tastes have been suggested as an independent category named alimentary. This narrative review will present and discuss evidence for macronutrient sensing throughout the alimentary canal and evidence of how each of the alimentary tastes may influence the consumption of foods.

A Fatty Acid Mouth Rinse Decreases Self-Reported Hunger and Increases Self-Reported Fullness in Healthy Australian Adults: A Randomized Cross-Over Trial

Fatty acid (FA) chemoreception in the oral cavity, known as fat taste, may trigger a satiety response that is homologous to FA chemoreception in the gastrointestinal tract. In addition, individuals with an impaired fat taste sensitivity are more likely to have an impaired satiety response. This study aimed to assess the effect of an FA mouth rinse on self-reported appetite, and to determine if the effect is modified by fat taste sensitivity. Thirty-one participants (age, 32.0 ± 8.4 y; body mass index (BMI), 26.1 ± 8.1 kg/m2) were studied on four separate days to evaluate the effect of a 20 mM oleic acid (OA) mouth rinse (in duplicate) compared to a control (in duplicate) on self-reported appetite by using a visual analogue scale (VAS) every 30 min for three hours following a standardized low-fat breakfast. The area under the curve ratings for fullness were greater (p = 0.003), and those for hunger were lower (p = 0.002) following the OA rinse compared to the control. The effect of the OA rinse was greater in individuals who were hypersensitive to fat taste compared to moderately sensitive and hyposensitive individuals for fullness (p < 0.010) and hunger (p < 0.010) ratings. In summary, an OA mouth rinse decreases self-reported hunger and increases self-reported fullness, particularly in those who are more sensitive to fat taste. FA receptors in the oral cavity may be potential targets to regulate appetite.

Predictors Linking Obesity and the Gut Microbiome (the PROMISE Study): Protocol and Recruitment Strategy for a Cross-Sectional Study on Pathways That Affect the Gut Microbiome and Its Impact on Obesity

Background

The prevalence of obesity has increased substantially over recent decades and is associated with considerable health inequalities. Although the causes of obesity are complex, key drivers include overconsumption of highly palatable, energy-dense, and nutrient-poor foods, which have a profound impact on the composition and function of the gut microbiome. Alterations to the microbiome may play a critical role in obesity by affecting energy extraction from food and subsequent energy metabolism and fat storage.

Objective

We report the study protocol and recruitment strategy of the PRedictors linking Obesity and the gut MIcrobiomE (PROMISE) study, which characterizes the gut microbiome in 2 populations with different metabolic disease risk (Pacific and European women) and different body fat profiles (normal and obese). It investigates (1) the role of gut microbiome composition and functionality in obesity and (2) the interactions between dietary intake; eating behavior; sweet, fat, and bitter taste perception; and sleep and physical activity; and their impact on the gut microbiome, metabolic and endocrine regulation, and body fat profiles.

Methods

Healthy Pacific and New Zealand (NZ) European women aged between 18 and 45 years from the Auckland region were recruited for this cross-sectional study. Participants were recruited such that half in each group had either a normal weight (body mass index [BMI] 18.5-24.9 kg/m²) or were obese (BMI ≥30.0 kg/m²). In addition to anthropometric measurements and assessment of the body fat content using dual-energy x-ray absorptiometry, participants completed sweet, fat, and bitter taste perception tests; food records; and sleep diaries; and they wore accelerometers to assess physical activity and sleep. Fasting blood samples were analyzed for metabolic and endocrine biomarkers and DNA extracted from fecal samples was analyzed by shotgun sequencing. Participants completed questionnaires on dietary intake, eating behavior, sleep, and physical activity. Data were analyzed using descriptive and multivariate regression methods to assess the associations between dietary intake, taste perception, sleep, physical activity, gut microbiome complexity and functionality, and host metabolic and body fat profiles.

Results

Of the initial 351 women enrolled, 142 Pacific women and 162 NZ European women completed the study protocol. A partnership with a Pacific primary health and social services provider facilitated the recruitment of Pacific women, involving direct contact methods and networking within the Pacific communities. NZ European women were primarily recruited through Web-based methods and special interest Facebook pages.

Conclusions

This cross-sectional study will provide a wealth of data enabling the identification of distinct roles for diet, taste perception, sleep, and physical activity in women with different body fat profiles in modifying the gut microbiome and its impact on obesity and metabolic health. It will advance our understanding of the etiology of obesity and guide future intervention studies involving specific dietary approaches and microbiota-based therapies.

Trial Registration

Australian New Zealand Clinical Trials Registry ACTRN12618000432213; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=370874

International Registered Report Identifier (IRRID)

RR1-10.2196/14529

Food Preferences in Cats: Effect of Dietary Composition and Intrinsic Variables on Diet Selection

Simple Summary

Cats tend to retain food preferences across their lifetime, but intrinsic variables could affect their diet choices so as to preserve internal homoeostasis. This work intended to study the feeding behavior of cats in relation to diet composition and some intrinsic variables (sex, age, and body weight) by analyzing data from a 10-year database of two-feeder food preference tests (2007–2017). Diet mineral components (calcium, crude fiber and ashes) affected food preferences negatively. In addition, the influence of body weight and sex manifested as lower food intake in both females and the heaviest cats (relative to bodyweight). However, only body weight affected food preferences, where the heaviest animals presented the higher preferences overall. During the cold season, animals (especially females) displayed higher food intake, whereas hot seasons increased male cat preferences for palatable diets, hence we observed an interaction between sex and climate season. In conclusion, understanding the relationship that both food composition and some intrinsic variables cats have with their diet preference could help in improving the formulation of specific pet food diets, so that these adequately satisfy the physiological and hedonic needs of domestic cats.

Abstract

A ten-year database of food preference tests (n = 1021; period 2007−2017) was used to explore the feeding behavior of domestic cats. Principal component (PC) analysis and linear regression between food nutrients and preferences (for the most preferred diet of each test; Diet A) were performed. Intake and preference for Diet A were analyzed by intrinsic cats’ variables and climate season. The PC1 (calcium (Ca), phosphorus (P), and ash), PC2 (lipids and ether extract) and PC4 (crude fiber; CF) had borderline significance (p < 0.06; β = −1.42, β = −1.56, and β = 2.68, respectively). Ash and CF contents presented negative correlations with food preference (rho = −0.269, p = 0.031; rho = −0.338, p = 0.006, respectively), and Ca had borderline significance and negative correlation with food preference (rho = −0.241, p = 0.054). Body weight and sex influenced the intake of Diet A, being lower for females (β = 11.758; p = 0.014) and heaviest cats (β = −5.490; p < 0.001). However, only body weight affected food preferences, where the heaviest cats had greater preferences for Diet A. Hot season decreased food intake (β = −2,117; p = 0.032), mostly in females (rho = −3.537; p = 0.002). Males had greater preferences for Diet A during hot seasons (β = 10.216; p = 0.023) and females presented similar preferences throughout the year (p = 0.950). Mineral contents, body weight and sex affected food intake and preferences of cats under the influence of climate season, probably explained by adaptive changes in food detection.

Exploring Associations between Interindividual Differences in Taste Perception, Oral Microbiota Composition, and Reported Food Intake

The role of taste perception, its relationship with oral microbiota composition, and their putative link with eating habits and food intake were the focus of the present study. A sample of 59 reportedly healthy adults (27 male, 32 female; age: 23.3 ± 2.6 years) were recruited for the study and taste thresholds for basic tastes, food intake, and oral microbiota composition were evaluated. Differences in taste perception were associated with different habitual food consumption (i.e., frequency) and actual intake. Subjects who were orally hyposensitive to salty taste reported consuming more bakery and salty baked products, saturated-fat-rich products, and soft drinks than hypersensitive subjects. Subjects hyposensitive to sweet taste reported consuming more frequently sweets and desserts than the hypersensitive group. Moreover, subjects hypersensitive to bitter taste showed higher total energy and carbohydrate intakes compared to those who perceived the solution as less bitter. Some bacterial taxa on tongue dorsum were associated with gustatory functions and with vegetable-rich (e.g., Prevotella) or protein/fat-rich diets (e.g., Clostridia). Future studies will be pivotal to confirm the hypothesis and the potential exploitation of oral microbiome as biomarker of long-term consumption of healthy or unhealthy diets.

Food Preferences in Dogs: Effect of Dietary Composition and Intrinsic Variables on Diet Selection

Simple Summary

Preference tests allow the study of some aspects of the feeding behavior of domestic dogs. However, besides sensorial proprieties of food, intrinsic characteristics of dogs may play a role in diet selection. The aim of this study was to describe the feeding behavior of dogs in relation to diet composition and their intrinsic variables (age, breed, sex, and body weight) by using a ten-year database of two-feeder food preference tests (2007–2017). The content of less digestible fractions like crude fiber and dry matter negatively affected dogs’ food preferences. In addition, animals’ weight and breed influenced dogs’ intake of the most preferred diets, where heaviest dogs presented lower intakes as did the Beagle breed in relation with both Boxer and Labrador Retrievers. Moreover, the hot season of the year decreased dogs’ intake of preferred diets. In terms of preferences, Boxers presented a lower preference for selected diets compared to the other breeds. Finally, age and sex did not affect dogs’ preference or intake of the foods selected. The understanding of the relationships between food composition and intrinsic variables of dogs with their diet selection could improve specific pet food formulation in order to satisfy animals’ physiological and hedonic needs.

Abstract

A ten-year food preference database (2007–2017) was used to relate food selection in dogs to the nutritional components of diets by doing a principal component analysis (PCA) and a linear regression between components obtained and dogs’ preferences. Intake and preference of preferred diets were analyzed by dogs’ sex, breed, age, body weight, and the season of the year (hot or cold). The fourth component after PCA presented a relation with food preferences (OR = −2.699, p = 0.026), showing negative correlations with crude fiber (rho = −0.196; P = 0.038) and dry matter (rho = −0.184; p = 0.049). Weight (OR = −1.35; p < 0.001), breed, both Boxer (OR = 10.62; p = 0.003) and Labrador Retriever (OR = 26.30; p < 0.001), and season (hot season) (OR = −5.27; p < 0.001) all influenced animals’ intake. Boxers presented a lower food preference compared to the other breeds (OR = −44.3; p < 0.001), while animals’ weight influenced preferences only in Boxers (OR = 2.02; p < 0.001). Finally, age and sex did not affect dogs’ preference or intake of preferred diets. Thus dry matter and fiber content have a negative impact on dogs’ food choices. Dogs’ weight, breed, and season affected food intake, but only breed affected dogs’ preferences, which is probably explained by adaptive changes in the detection, metabolization, and learning of nutritive food cues.

Expression of the candidate fat taste receptors in human fungiform papillae and the association with fat taste function

Significant experimental evidence supports fat as a taste modality; however, the associated peripheral mechanisms are not well established. Several candidate taste receptors have been identified, but their expression pattern and potential functions in human fungiform papillae remain unknown. The aim of this study is to identify the fat taste candidate receptors and ion channels that were expressed in human fungiform taste buds and their association with oral sensory of fatty acids. For the expression analysis, quantitative RT-PCR (qRT-PCR) from RNA extracted from human fungiform papillae samples was used to determine the expression of candidate fatty acid receptors and ion channels. Western blotting analysis was used to confirm the presence of the proteins in fungiform papillae. Immunohistochemistry analysis was used to localise the expressed receptors or ion channels in the taste buds of fungiform papillae. The correlation study was analysed between the expression level of the expressed fat taste receptors or ion channels indicated by qRT-PCR and fat taste threshold, liking of fatty food and fat intake. As a result, qRT-PCR and western blotting indicated that mRNA and protein of CD36, FFAR4, FFAR2, GPR84 and delayed rectifying K+ channels are expressed in human fungiform taste buds. The expression level of CD36 was associated with the liking difference score (R −0·567, β=−0·04, P=0·04) between high-fat and low-fat food and FFAR2 was associated with total fat intake (ρ=−0·535, β=−0·01, P=0·003) and saturated fat intake (ρ=−0·641, β=−0·02, P=0·008).

The Role of the Japanese Traditional Diet in Healthy and Sustainable Dietary Patterns around the World

As incomes steadily increase globally, traditional diets have been displaced by diets that are usually animal-based with a high content of “empty calories” or refined sugars, refined fats, and alcohol. Dietary transition coupled with the expansion of urbanization and lower physical activity have been linked to the global growth in the prevalence of obesity, overweight and life style-related non-communicable diseases. The challenge is in how to reverse the trend of high consumption of less healthy food by more healthful and more environmentally sustainable diets. The increasing recognition that each individual has specific needs depending on age, metabolic condition, and genetic profile adds complexity to general nutritional considerations. If we were to promote the consumption of low-energy and low salt but nutritious diets, taste becomes a relevant food quality. The Japanese traditional diet (Washoku), which is characterized by high consumption of fish and soybean products and low consumption of animal fat and meat, relies on the effective use of umami taste to enhance palatability. There may be a link between Washoku and the longevity of the people in Japan. Thus Washoku and umami may be valuable tools to support healthy eating.

Could Vaping be a New Weapon in the Battle of the Bulge?

IMPLICATIONS

Obesity is set to overtake tobacco smoking in many countries as the primary cause of several high-cost diseases. Tobacco smoking mitigates weight gain through nicotine's effect on the brain and metabolism. Smoking, however, is associated with many illnesses and premature death and appropriately has been discouraged leading to declining prevalence rates. This article explores the emerging perception that vaping electronic cigarettes with nicotine and flavors could deliver similar appetite and weight control effects as smoking. The potential to reduce risks associated with excess weight deserves exploration. An initial research agenda is suggested.

Fat Sensation: Fatty Acid Taste and Olfaction Sensitivity and the Link with Disinhibited Eating Behaviour

Perception of fat taste, aroma, and texture are proposed to influence food preferences, thus shaping dietary intake and eating behaviour and consequently long-term health. In this study, we investigated associations between fatty acid taste, olfaction, mouthfeel of fat, dietary intake, eating behaviour, and body mass index (BMI). Fifty women attended three sessions to assess oleic acid taste and olfaction thresholds, the olfactory threshold for n-butanol and subjective mouthfeel ratings of custard samples. Dietary intake and eating behaviour were evaluated using a Food Frequency and Three-Factor Eating Questionnaire, respectively. Binomial regression analysis was used to model fat taste and olfaction data. Taste and olfactory detection for oleic acid were positively correlated (r = 0.325; p < 0.02). Oleic acid taste hypersensitive women had significantly increased n-butanol olfactory sensitivity (p < 0.03). The eating behaviour disinhibition and BMI were higher in women who were hyposensitive to oleic acid taste (p < 0.05). Dietary intake of nuts, nut spreads, and seeds were significantly correlated with high olfactory sensitivity to oleic acid (p < 0.01). These findings demonstrate a clear link between fatty acid taste sensitivity and olfaction and suggest that fat taste perception is associated with specific characteristics of eating behaviour and body composition.

Fat Taste Sensitivity Is Associated with Short-Term and Habitual Fat Intake

Evidence suggests individuals less sensitive to fat taste (high fat taste thresholds (FTT)) may be overweight or obese and consume greater amounts of dietary fat than more sensitive individuals. The aims of this study were to assess associations between FTT, anthropometric measurements, fat intake, and liking of fatty foods. FTT was assessed in 69 Australian females (mean age 41.3 (15.6) (SD) years and mean body mass index 26.3 (5.7) kg/m²) by a 3-alternate forced choice methodology and transformed to an ordinal scale (FT rank). Food liking was assessed by hedonic ratings of high-fat and reduced-fat foods, and a 24-h food recall and food frequency questionnaire was completed. Linear mixed regression models were fitted. FT rank was associated with dietary % energy from fat ( β ^ = 0.110 [95% CI: 0.003, 0.216]), % energy from carbohydrate ( β ^ = -0.112 [-0.188, -0.035]), and frequency of consumption of foods per day from food groups: high-fat dairy ( β ^ = 1.091 [0.106, 2.242]), meat & meat alternatives ( β ^ = 0.669 [0.168, 1.170]), and grain & cereals ( β ^ = 0.771 [0.212, 1.329]) (adjusted for energy and age). There were no associations between FT rank and anthropometric measurements or hedonic ratings. Therefore, fat taste sensitivity appears to be associated with short-term fat intake, but not body size in this group of females.

Genetics of fat intake in the determination of body mass

Body mass and fat intake are multifactorial traits that have genetic and environmental components. The gene with the greatest effect on body mass is FTO (fat mass and obesity-associated), but several studies have shown that the effect of FTO (and of other genes) on body mass can be modified by the intake of nutrients. The so-called gene–environment interactions may also be important for the effectiveness of weight-loss strategies. Food choices, and thus fat intake, depend to some extent on individual preferences. The most important biological component of food preference is taste, and the role of fat sensitivity in fat intake has recently been pointed out. Relatively few studies have analysed the genetic components of fat intake or fatty acid sensitivity in terms of their relation to obesity. It has been proposed that decreased oral fatty acid sensitivity leads to increased fat intake and thus increased body mass. One of the genes that affect fatty acid sensitivity is CD36 (cluster of differentiation 36). However, little is known so far about the genetic component of fat sensing. We performed a literature review to identify the state of knowledge regarding the genetics of fat intake and its relation to body-mass determination, and to identify the priorities for further investigations.

Comparisons of Fatty Acid Taste Detection Thresholds in People Who Are Lean vs. Overweight or Obese: A Systematic Review and Meta-Analysis

Given the increasing evidence that supports the ability of humans to taste non-esterified fatty acids (NEFA), recent studies have sought to determine if relationships exist between oral sensitivity to NEFA (measured as thresholds), food intake and obesity. Published findings suggest there is either no association or an inverse association. A systematic review and meta-analysis was conducted to determine if differences in fatty acid taste sensitivity or intensity ratings exist between individuals who are lean or obese. A total of 7 studies that reported measurement of taste sensations to non-esterified fatty acids by psychophysical methods (e.g.,studies using model systems rather than foods, detection thresholds as measured by a 3-alternative forced choice ascending methodology were included in the meta-analysis. Two other studies that measured intensity ratings to graded suprathreshold NEFA concentrations were evaluated qualitatively. No significant differences in fatty acid taste thresholds or intensity were observed. Thus, differences in fatty acid taste sensitivity do not appear to precede or result from obesity.

Relative Effects of Sensory Modalities and Importance of Fatty Acid Sensitivity on Fat Perception in a Real Food Model

INTRODUCTION

Fat can be perceived through mouthfeel, odour and taste, but the influence of these modalities on fat perception remains undefined. Fatty acids are stimuli and individual sensitivity to fatty acids varies. Studies show association between fatty acid sensitivity, dietary intake and BMI, but results are conflicting. Therefore, this study examined this association, and the effect of modalities on fat perception.

METHODS

Two sub-studies were conducted. In study 1 (n = 46), fat intensity was assessed by milk/cream mixtures varying by five fat levels. Fat intensity was rated under four conditions: mouthfeel odour-masked, mouthfeel-masked, odour masked and with no masking. Mouthfeel masking was achieved using thickener and paraffin, odour masking using nose-clips. Fatty acid sensitivity was measured by 3-AFC staircase method using milk containing oleic acid (0.31-31.4 mM). In study 2 (n = 51), more fat levels were added into the intensity rating. A 2-AFC discrimination test was used to confirm whether fat levels could be distinguished. In the sensitivity test, a wider range of oleic acid was included.

RESULTS

Fat intensity was rated higher without nose clips (p < 0.0001), implying that odour increased fat perception. Mouthfeel-masked samples were rated higher, showing that increased viscosity and lubricity enhanced fat perception (p < 0.0001). Participants could distinguish fat levels based on "taste" in rating tests and 2-AFC tests. Participants were divided into high-/medium-/low-sensitivity groups. No significant difference was found in fat intensity between groups; however, the high-sensitivity group discriminated more fat levels. No association between sensitivity groups, nutrient intake or BMI was found.

CONCLUSION

Mouthfeel and odour can enhance fat perception. Fat level can be discriminated based on taste.

Salt Promotes Passive Overconsumption of Dietary Fat in Humans

BACKGROUND

Excess fat consumption has been linked to the development of obesity. Fat and salt are a common and appetitive combination in food; however, the effect of either on food intake is unclear. Fat taste sensitivity has been negatively associated with dietary fat intake, but how fat taste sensitivity influences the intake of fat within a meal has, to our knowledge, not yet been investigated.

OBJECTIVES

Our objectives were, first, to investigate the effects of both fat and salt on ad libitum food intake and, second, to investigate the effects of fat taste sensitivity on satiation responses to fat and whether this was affected by salt.

METHODS

Forty-eight healthy adults [16 men and 32 women, aged 18-54 y, body mass index (kg/m(2)): 17.8-34.4] were recruited and their fat taste sensitivity was measured by determination of the detection threshold of oleic acid (18:1n-6). In a randomized 2 × 2 crossover design, participants attended 4 lunchtime sessions after a standardized breakfast. Meals consisted of elbow macaroni (56%) with sauce (44%); sauces were manipulated to be1) low-fat (0.02% fat, wt:wt)/low-salt (0.06% NaCl, wt:wt),2) low-fat/high-salt (0.5% NaCl, wt:wt),3) high-fat (34% fat, wt:/wt)/low-salt, or4) high-fat/high-salt. Ad libitum intake (primary outcome) and eating rate, pleasantness, and subjective ratings of hunger and fullness (secondary outcomes) were measured.

RESULTS

Salt increased food and energy intakes by 11%, independent of fat concentration (P= 0.022). There was no effect of fat on food intake (P= 0.6), but high-fat meals increased energy intake by 60% (P< 0.001). A sex × fat interaction was found (P= 0.006), with women consuming 15% less by weight of the high-fat meals than the low-fat meals. Fat taste sensitivity was negatively associated with the intake of high-fat meals but only in the presence of low salt (fat taste × salt interaction on delta intake of high-fat - low-fat meals;P= 0.012).

CONCLUSIONS

The results suggest that salt promotes passive overconsumption of energy in adults and that salt may override fat-mediated satiation in individuals who are sensitive to the taste of fat. This trial was registered at the Australian New Zealand Clinical Trials Registry (www.anzctr.org.au) as ACTRN12615000048583.

Effects of Salt and Fat Combinations on Taste Preference and Perception

Fat and salt are a common and attractive combination in food and overconsumption of either is associated with negative health outcomes. The major aim was to investigate contributions and interactions of salt and fat on taste pleasantness and perception. The minor aim was to investigate individual fat taste sensitivity (detection threshold of oleic acid [C18:1]) on pleasantness for fat. In a complete factorial design, 49 participants (18–54 years, 12 males) tasted tomato soups with 4 different fat concentrations (0–20%) and 5 different salt concentrations (0.04–2.0%). The preferred concentration and the discrimination ability for both fat and salt were determined by ranking tests. Results show that salt and fat affected pleasantness separately (P < 0.01), with salt having the strongest effect. Fat concentrations 0%, 5%, and 10% did not differ in pleasantness, whereas 20% was less pleasant (P < 0.05). There were no interactions for fat and salt on pleasantness or saltiness and fattiness intensity. Fat taste sensitive participants preferred lower fat concentrations than less sensitive participants (P = 0.008). In conclusion, the strong effect of salt on pleasantness in this study suggests that salt, rather than fat, play a major role in the attraction to savory fatty foods.

Controversies in fat perception

Nutritional fat is one of the most controversial topics in nutritional research, particularly against the background of obesity. Studies investigating fat taste perception have revealed several associations with sensory, genetic, and personal factors (e.g. BMI). However, neuronal activation patterns, which are known to be highly sensitive to different tastes as well as to BMI differences, have not yet been included in the scheme of fat taste perception. We will therefore provide a comprehensive survey of the sensory, genetic, and personal factors associated with fat taste perception and highlight the benefits of applying neuroimaging research. We will also give a critical overview of studies investigating sensory fat perception and the challenges resulting from multifaceted methodological approaches. In conclusion, we will discuss a multifactorial approach to fat perception to gain a better understanding of the underlying mechanisms that cause varying fat sensitivity which could be responsible for overeating. Such knowledge might be beneficial in new treatment strategies for obesity and overweight.

No Difference in Perceived Intensity of Linoleic Acid in the Oral Cavity between Obese and Nonobese Individuals

Findings from studies examining interactions between fat taste and dietary fat intake or body weight are mixed. A convenience sample of 735 visitors to the Denver Museum of Nature & Science ≥8 years old rated the taste intensity of edible taste strips impregnated with varying concentrations (%v/v) of linoleic acid (LA) (blank = 0.0, low = 0.06, medium = 0.15, high = 0.38). Percent body fat (BF%) was measured using bioelectrical impedance. Fat taste intensity was rated as significantly different across all concentrations (P < 0.001) except between the blank and low concentrations (P = 0.1). Ratings increased monotonically across concentrations. Children (<18 years; N = 180) rated all concentrations as more intense than adults (P < 0.001 for all). Women and girls rated the highest concentration as more intense than men and boys (P < 0.02 for all). BF% was not correlated with fat taste intensity ratings. Self-reported dietary intake indicated that obese individuals’ intensity ratings for medium and high concentrations of LA were inversely related to recent mono- and poly-unsaturated fat exposure (r = −0.19 to −0.27; P < 0.03 for all). No such associations were observed in the nonobese group. Findings suggest that factors other than simple adiposity status influence fat taste intensity ratings, and that participants in fat taste studies should receive standardized meals prior to testing.

The influence of herbs, spices, and regular sausage and chicken consumption on liking of reduced fat breakfast and lunch items

Adults often consume more fat than is recommended. We examined factors that may improve liking of reduced fat and reduced saturated fat foods, including the addition of herbs and spices and habitual consumption of different high-fat and low-fat food items. We randomized adults to taste 3 different conditions: full fat (FF), reduced fat with no added spice (RF), and reduced fat plus spice (RFS). Subjects rated their liking of French toast, sausage and the overall meal, or chicken, vegetables, pasta, and the overall meal on a 9-point hedonic Likert scale. Overall liking of the RF breakfast and lunch meals were lower than the FF and RFS versions (breakfast: 6.50 RF compared with 6.84 FF, P = 0.0061; 6.50 RF compared with 6.82 RFS, P = 0.0030; lunch: 6.35 RF compared with 6.94 FF, P < 0.0001; 6.35 RF compared with 6.71 RFS, P = 0.0061). RFS and FF breakfast and lunch meals, French toast, chicken, and vegetable likings were similar. FF and RFS conditions were liked more than RF for the breakfast and lunch meals, French toast, chicken entrée, and vegetables. Liking of all 3 sausage conditions was similar. FF pasta was liked more than RFS and RF (7.47 FF compared with 6.42 RFS, P < 0.0001; 7.47 FF compared with 6.47 RF, P < 0.0001). Habitual consumption of roasted chicken was associated with reduced liking of FF chicken (r = -0.23, P = 0.004) and FF pasta (r = -0.23, P = 0.005). Herbs and spices may be useful for improving the liking of lower fat foods and helping Americans maintain a diet consistent with the U.S. Dietary Guidelines.

PRACTICAL APPLICATION

Americans consume more fat than is recommended in the Dietary Guidelines for Americans. This study shows that you can take foods like French toast, chicken, or a vegetable side and cut the fat and calories by up to 50% while restoring flavor with herbs and spices. People typically use butter, cheese, or fatty meat to enhance the flavor of their food. We found that even when we reduced the fat in our meals by using lower fat dairy and meat products but then added herbs and spices, we were able to deliver the flavor people desire for a fraction of the calories.