Non-invasive vagus nerve stimulation normalizes food liking and improves liking ratings in depression

Introduction: The vagus nerve plays a prominent role in the regulation of food reward and energy metabolism. However, previous studies using vagus nerve stimulation yielded conflicting results regarding changes in food reward in healthy participants and participants with major depressive disorder (MDD), for which vagal nerve stimulation is an effective treatment. Methods: We investigated the acute effects of right transcutaneous auricular vagus nerve stimulation (taVNS) on ratings of liking and wanting of food and non-food items in 63 participants, including 31 patients with MDD. To test for taVNS-induced changes and interactions with between-subject variables group (MDD vs. healthy controls) and questionnaire scores as well as within-subject variables, we performed linear mixed-effects analysis. In addition, we assessed whether individual taVNS-induced changes in food reward ratings were dependent on average ratings.Results: taVNS increased liking of food cues in participants with MDD (p= 0.023), but not in healthy participants (p= 0.657). Specifically, taVNS induced larger improvements in liking ratings with increasing scores of anhedonia (p= 0.029). Notably, across all participants, taVNS reduced the variance of food liking compared to sham, suggesting that taVNS normalizes extreme liking ratings towards moderate levels (p = 0.039).Discussion: Our results show that taVNS acutely ameliorates hedonic responses in MDD suggesting that it could provide an effective treatment of anhedonia. Since anhedonia is difficult to treat with conventional therapies, taVNS may provide a powerful adjuvant to rapidly improve motivational deficiencies.

Does Responsiveness to Basic Tastes Influence Preadolescents’ Food Liking? Investigating Taste Responsiveness Segment on Bitter-Sour-Sweet and Salty-Umami Model Food Samples

The objective of this study was to investigate the relationships between taste responsiveness and food liking in preadolescents. Model food samples of grapefruit juice (GF) and vegetable broth (VB) modified with four additions of sucrose and sodium chloride, respectively, were employed. Intensity perception for sweetness, sourness, and bitterness were measured in GF while saltiness and umami were measured in VB. The children (N = 148) also completed food choice, familiarity, stated liking and neophobia questionnaires. The test was conducted at school, with instructions provided remotely via video call. Four segments were defined differing in basic taste responsiveness. Segments and sucrose concentrations significantly affected liking for GF, while no significant effect of segments and sodium chloride concentrations occurred on liking for VB. An increasing sucrose concentration was positively associated with liking for GF only in the segment with low responsiveness to bitter and sour tastes. No significant differences across segments were found for food choice, familiarity, stated liking, and neophobia. Conclusively, relationships between taste responsiveness and liking are product and basic taste-dependent in addition to being subject-dependent. Strategies to improve acceptance by using sucrose as a suppressor for warning sensations of bitterness and sourness can be more or less effective depending on individual responsiveness to the basic tastes.

Large-scale genome-wide association study of food liking reveals genetic determinants and genetic correlations with distinct neurophysiological traits.

Variable preferences for different foods are among the main determinants of their intake and are influenced by many factors, including genetics. Despite considerable twins' heritability, studies aimed at uncovering food-liking genetics have focused mostly on taste receptors. Here, we present the first results of a large-scale genome-wide association study of food liking conducted on 161,625 participants from UK Biobank. Liking was assessed over 139 specific foods using a 9-point hedonic scale. After performing GWAS, we used genetic correlations coupled with structural equation modelling to create a multi-level hierarchical map of food liking. We identified three main dimensions: high caloric foods defined as "Highly palatable", strong-tasting foods ranging from alcohol to pungent vegetables, defined as "Learned" and finally "Low caloric" foods such as fruit and vegetables. The "Highly palatable" dimension was genetically uncorrelated from the other two, suggesting that two independent processes underlie liking high reward foods and the Learned/Low caloric ones. Genetic correlation analysis with the corresponding food consumption traits revealed a high correlation, while liking showed twice the heritability compared to consumption. For example, fresh fruit liking and consumption showed a genetic correlation of 0.7 with heritabilities of 0.1 and 0.05, respectively. GWAS analysis identified 1401 significant food-liking associations located in 173 genomic loci, with only 11 near taste or olfactory receptors. Genetic correlation with morphological and functional brain data (33,224 UKB participants) uncovers associations of the three food-liking dimensions with non-overlapping, distinct brain areas and networks, suggestive of separate neural mechanisms underlying the liking dimensions. In conclusion, we created a comprehensive and data-driven map of the genetic determinants and associated neurophysiological factors of food liking beyond taste receptor genes.

Both Food Liking and Energy Density Influence Children's Portion Selection

Objectives Food liking influences food choice and the most-liked foods are often energy dense. Previous studies found that both food liking and energy density predicted the size of portions selected by adults. To extend these findings, we investigated the independent and combined effects of food liking and energy density on portion selection in children. Methods In two laboratories, 67 children aged 7–16 years (49% girls; 16% with overweight or obesity) completed a computerized survey to assess characteristics of 20 common foods. Children were shown images of the foods and used 100-point scales to rate how much they liked the food (liking) and how much they would eat at a specified meal (portion selection). The energy density (ED) of the foods ranged from 0.3 to 4.9 kcal/g. The survey displayed five images of food amounts at 10%, 30%, 50%, 70%, and 90% of the scale. The portion size of the 50% image was used as the reference amount and was based on mean intake for similar aged children from a U.S. national survey. Individual energy needs were estimated using the Dietary Reference Intake equations. Results There were independent effects of children's liking ratings and food ED, which did not interact to influence portion selection (p = 0.21). Across all foods, food liking had a strong effect on the portion size selected (p < 0.0001); the magnitude of this effect depended on age (−0.04 ± 0.02; p = 0.015). Food energy density had a smaller effect (p = 0.04) that also depended on age (−0.39 ± 0.15; p = 0.010). Younger children selected larger portions (relative to the reference portion) from higher-ED foods than lower-ED foods; conversely, older children selected smaller portions from higher-ED foods. The effects of age remained significant when adjusted for individual energy needs. The effects on portion selection of either food liking or energy density were not influenced by children's sex, BMI-for-age percentile or BMI z-score. Conclusions These results confirm that food liking and food ED are significant determinants of portion selection in children. The finding that liking affected portion selection even for low-ED foods has implications for promoting healthy eating habits in children. Serving larger portions of well-liked low-ED foods such as fruits and vegetables can be a strategy to promote children's intake. Funding Sources NCRR, NCATS, NIDDK.

Oral Sensitivity to Flowability and Food Neophobia Drive Food Preferences and Choice

The study aimed to investigate the role of sensitivity to flowability on food liking and choice, the relationship between sensitivity to flowability and food neophobia, and its role in food liking. Five chocolate creams were prepared with different levels of flowability, and rheological measurements were performed to characterise them. One hundred seventy-six subjects filled in the Food Neophobia Scale and a food choice questionnaire (FCq). The FCq was developed to evaluate preferences within a pair of food items similar in flavour but different in texture. Secondly, the subjects evaluated their liking for creams (labelled affective magnitude (LAM) scale) and the flowability intensity (generalised labelled magnitude (gLM) scale). The subjects were clustered into three groups of sensitivity and two groups of choice preference. The effect of individual flowability sensitivity on food choice was investigated. Finally, the subjects were clustered into two groups according to their food neophobia level. The sensitivity to flowability significantly affected the liking of chocolate creams and the solid food choice. The liking of chocolate creams was also affected by the individual level of neophobia (p = 0.01), which, in turn, was not correlated to flowability sensitivity. These results confirm that texture sensitivity and food neophobia affect what a person likes and drives what a person chooses to eat.