Non-food Odors Research Articles

Olfactory performance and odor liking are negatively associated with food neophobia in children aged between 3 and 9 years

BackgroundChild food neophobia, i.e., rejection or avoidance of novel foods at a young age, is a prevalent nutrition problem that affects the quality of children’s diet and impedes the development of healthy food preferences. Sensory sensitivity can relate to the degree of food neophobia, but previous studies rarely focused on the olfactory component of this problem in children.ObjectiveWe aimed to thoroughly examine the relationship between various aspects of olfactory sensitivity and food neophobia in children.Methods246 children aged between three and nine years took part in a food neophobia assessment as well as in a comprehensive, psychophysical olfactory testing.ResultsWe found that certain smell perception aspects such as lower odor liking, poorer odor identification ability as well as lower sensitivity to an unknown non-food odor all significantly predicted higher food neophobia in children. Among individual characteristics of either a child or a caregiver, only the child’s age significantly and positively predicted food neophobia. The exploratory model looking into the role of family environment factors predicting self-reported food neophobia in children revealed that food neophobia was associated with lower control given to a child in this child’s feeding process, as well as with a more frequent use of food as a reward in feeding.ConclusionsWe suggest that suppressed olfactory perception and performance can play a unique role in child nutritional difficulties. The study inspires further considerations of olfaction-engaging interventions to counteract food-neophobia in children.

Hunger signalling in the olfactory bulb primes exploration, food-seeking and peripheral metabolism

ObjectiveAlthough the metabolic state of an organism affects olfactory function, the precise mechanisms and their impact on behavior and metabolism remain unknown. Here, we assess whether ghrelin receptors (GHSRs) in the olfactory bulb (OB) increase olfactory function and influence foraging behaviors and metabolism. MethodsWe performed a detailed behavioural and metabolic analysis in mice lacking GHSRs in the OB (OBGHSR deletion). We also analsyed OB scRNA-seq and spatial transcriptomic datasets to assess GHSR+ cells in the main and accessory olfactory bulbs, as well as the anterior olfactory nucleus. ResultsOBGHSR deletion affected olfactory discrimination and habituation to both food and non-food odors. Anxiety-like and depression-like behaviors were significantly greater after OBGHSR deletion, whereas exploratory behavior was reduced, with the greatest effect under fasted conditions. OBGHSR deletion impacted feeding behavior as evidenced by altered bout number and duration, as well as buried food-seeking. OBGHSR deletion increased body weight and fat mass, spared fat utilisation on a chow diet and impaired glucose metabolism indicating metabolic dysfunction. Cross referenced analysis of OB scRNA-seq and spatial transcriptomic datasets revealed GHSR+ glutamate neurons in the main and accessory olfactory bulbs, as well as the anterior olfactory nucleus. Ablation of glutamate neurons in the OB reduced ghrelin-induced food finding and phenocopied results seen after OBGHSR deletion. ConclusionsOBGHSRs help to maintain olfactory function, particularly during hunger, and facilitate behavioral adaptations that optimise food-seeking in anxiogenic environments, priming metabolic pathways in preparation for food consumption.

Children's odor pleasantness ratings may not differ according to pubertal status: Preliminary results from a sample of 11–14-year-old Czech children

Puberty tends to be viewed as a “turning point” in hedonic perception of body odor (BO)-related smells. The pubertal stage, a potential proxy for the underlying physiological changes, may contribute to variation in odor hedonic perception. Other potential modulators of odor hedonics are general semantic knowledge about odors (which also tends to be subsumed under the term “age”) and perceived odor intensity. The present cross-sectional study examined differences in hedonic odor perception across puberty in 205 Czech children aged 11–14 (89 boys). We investigated whether children differ in the hedonic appraisal of BO-related (16-androstenes and castoreum control), but also food and non-food odors according to their pubertal (penis/breast and pubic hair) development and general semantic knowledge about odors (operationalized as odor identification), controlling for age and perceived odor intensity. As a subsidiary aim, we examined variation in odor identification. We asked the children to self-stage themselves using drawings depicting Tanner's penis/breast and pubic hair stages of pubertal development, estimated their general semantic knowledge about odors with a Sniffin’ Sticks identification test, and obtained their pleasantness and intensity ratings of body odor-related, food, a non-food smells. We found that the participants’ ratings of the 16-androstenes and those of the perceptually similar odor of castoreum differed according to perceived intensity and, in the latter case, in boys vs. girls as well, but there were no influences of pubertal status or odor identification on the perceived pleasantness. Similarly, hedonic appraisal of non-food (but not food) odors was only influenced by perceived intensity. Regarding odor identification, differences between boys and girls were limited to younger children and did not become more marked throughout puberty. Perceived pleasantness of odors, irrespective of whether they are associated with body smells, food, or other, does not appear to vary across puberty, and boys and girls seem to achieve similar levels of semantic odor knowledge as they grow up.

Altered neural representation of olfactory food reward in the nucleus accumbens after acute stress

Acute stress impairs reward processing. The nucleus accumbens (NAcc) plays an important role in the processing of primary rewards such as food. The present study investigates how acute stress affects the olfactory food reward processing in the NAcc using the representational similarity analysis. Forty-eight participants underwent an olfactory fMRI session following either an acute psychosocial stress (N = 24; stress group) or a control (N = 24; control group). Brain activation was recorded during the anticipatory and the perceptual phases of high-calorie food, low-calorie food, and non-food odor stimuli. Compared to the control group, the stress group rated the high-calorie food odor as significantly more pleasant (p = 0.005). In the NAcc, acute stress significantly reduced the dissimilarity of food and non-food odors in the perceptual phase (p = 0.027) and marginally reduced the dissimilarity of high- and low-calorie foods in the anticipatory phase (p = 0.095). Significant negative correlations were observed between the level of NAcc representational differentiation for high- and low-calorie food odors during perception and the difference in pleasantness ratings between high- and low-calorie food odors (r = -0.40, p = 0.005). These findings suggest that acute stress may impair participants’ ability to discriminate between olfactory food rewards, leading individuals to seek out more palatable foods in stressful situations in order to maintain positive emotions.

Developmental changes in food and non-food odor importance – Data from Scotland and Pakistan

Developmental changes in objective olfactory abilities are well-documented, but the subjective importance of odors and olfaction from a developmental perspective has received less scientific interest. Here, in Scotland and Pakistan, we tested the importance of olfaction in 704 respondents (48.9% females) aged between 5 and 75 years old using a novel questionnaire. The scale comprised 18 items targeting six main functions of odor perception: appetite and regulation of food intake, pathogen and hazard avoidance, mating, social relations, bonding, and sensual pleasure. We found that the importance of olfaction was well-developed in children and often exceeded that of the adult samples. Notably, the ingestion-related element of olfactory importance seems to be observable from an early age. Our findings complement and advance the theory of human olfactory learning and help us understand the significance of smells from a developmental perspective.

The neural substrates responsible for food odor processing: an activation likelihood estimation meta-analysis.

In many species including humans, food odors appear to play a distinct role when compared with other odors. Despite their functional distinction, the neural substrates responsible for food odor processing remain unclear in humans. This study aimed to identify brain regions involved in food odor processing using activation likelihood estimation (ALE) meta-analysis. We selected olfactory neuroimaging studies conducted with sufficient methodological validity using pleasant odors. We then divided the studies into food and non-food odor conditions. Finally, we performed an ALE meta-analysis for each category and compared the ALE maps of the two categories to identify the neural substrates responsible for food odor processing after minimizing the confounding factor of odor pleasantness. The resultant ALE maps revealed that early olfactory areas are more extensively activated by food than non-food odors. Subsequent contrast analysis identified a cluster in the left putamen as the most likely neural substrate underlying food odor processing. In conclusion, food odor processing is characterized by the functional network involved in olfactory sensorimotor transformation for approaching behaviors to edible odors, such as active sniffing.

Chronic stress is associated with reward and emotion-related eating behaviors in college students.

Stress is related to altered olfactory perception and eating behaviors. The current study investigated the association between chronic stress, food reward and perception of food and non-food odors among college students. Sixty-one participants completed the Perceived Stress Scale (PSS) and the Brief Daily Stressors Screening Tool (BDSST). The detective threshold and suprathreshold perception (pleasantness, intensity, and familiarity) of two food (chocolate, strawberry) odors and a non-food (rose) odor were measured. Food reward and macronutrient preference were measured using the computerized Leeds Food Preference Questionnaire and the Macronutrient and Taste Preference Ranking task, respectively. Reward-related eating, emotional eating and eating-related inhibitory control were measured by the Dutch Eating Behavior Questionnaire (DEBQ) and the Reward-Based Eating Drive Scale (RED) scales. Neither the perceived stress or the severity of daily life stressor exposure was related to odor sensitivity, however, the PSS score was significantly correlated with pleasantness for strawberry odor (r = 0.329, p = 0.013). Chronic stress (PSS and BDSST scores) was significantly correlated with the DEBQ emotional eating and reward-related eating measured by RED (all ps < 0.01). Moreover, the BDSST score was negatively correlated with subjective liking for low-calorie sweet foods (r = -0.46, p < 0.001). Together, our preliminary results suggest disassociated effect of chronic stress on odor perception and eating behaviors.

Diet and odor hedonic ratings: comparative study between vegetarians, flexitarians, and omnivores

ABSTRACT Objectives: Odor hedonic perception is well known to exhibit great variability and to depend on several parameters, i.e. stimulus, context, and subject characteristics. As hedonic perception (pleasant/unpleasant character) of food odors is considered one of the most prominent dimensions in eating behavior, the question of hedonic variability in this context arises. Thus, the aim of the present study was to compare odor hedonic ratings in three populations with regard to diet (i.e. omnivore, vegetarian, and flexitarian diets). Methods: Four categories of odors were compared: meat, vegetable, other food, and non-food odors. Results: The results showed that vegetarian and flexitarian individuals rated meat odors as more unpleasant than omnivores, while no significant difference was found for other categories of odors. Discussion: The question of whether the diet influences the hedonic perception or/and inversely is discussed, regarding several aspects of food consumption such as eating disorders, food education, … and could further serve to manage eating behaviors. Practical applications: This study evidenced that vegetarians and flexitarians specifically rated meat odors as being more unpleasant than those of omnivores. Because of the growing number of vegetarians and flexitarians in the general population, it could be suggested to take into account the odor hedonic perception (especially regarding food odors) in studies related to diets. Besides, the present results could further serve research in several aspects of food consumption such as eating disorders (anorexia, bulimia … etc.) or food education as well as the management of eating behaviors, especially in an elderly population.

Olfactory decoding is positively associated with ad libitum food intake in sated humans

The role of olfaction in eating behavior and body weight regulation is controversial. Here we reanalyzed data from a previous functional magnetic resonance imaging study to test whether central olfactory coding is associated with hunger/satiety state, food intake, and change in body weight over one year in healthy human adults. Since odor quality and category are coded across distributed neural patterns that are not discernible with traditional univariate analyses, we used multi-voxel pattern analyses to decode patterns of brain activation to food versus nonfood odors. We found that decoding accuracies in the piriform cortex and amygdala were greater in the sated compared to hungry state. Sated decoding accuracies in these and other regions were also associated with post-scan ad libitum food intake, but not with weight change. These findings demonstrate that the fidelity of olfactory decoding is influenced by meal consumption and is associated with immediate food intake, but not longer-term body weight regulation.

Food olfactory cues reactivity in individuals with obesity and the contribution of alexithymia

Obesity has been associated with increased reward sensitivity to food stimuli, but a few studies have addressed this issue by using odors. This study investigated whether obesity is associated with increased liking and wanting of food odors and whether alexithymia, a psychological construct characterized by diminished affective abilities, contributes to altered responsiveness to food. Liking and wanting for food and pleasant non-food odors were measured through explicit (self-report ratings) and implicit measures (heart rate and skin conductance) in 23 women with healthy weight (HW) and 20 women with overweight/obesity (OW/OB). Differently from the HW group, the OW/OB group explicitly liked food odors less than non-food odors; but, at the implicit level, there were no differences in heart rate response for both types of odors, indicating that they were equally liked. Moreover, at variance with the HW group, the OW/OB group did not exhibit increased skin conductance response for food compared to nonfood odors. Alexithymia was associated with increased implicit liking and explicit wanting of food odors, in particular in the HW group. These findings show that obesity is characterized by high levels of implicit food liking and low levels of implicit food wanting. Moreover, both affective and motivational responses to food reward seem to be affected by alexithymia, which should be taken into account by studies evaluating the effect of cue exposure intervention for obesity treatment.

Olfactory perceptual decision-making is biased by motivational state.

Growing evidence suggests that internal factors influence how we perceive the world. However, it remains unclear whether and how motivational states, such as hunger and satiety, regulate perceptual decision-making in the olfactory domain. Here, we developed a novel behavioral task involving mixtures of food and nonfood odors (i.e., cinnamon bun and cedar; pizza and pine) to assess olfactory perceptual decision-making in humans. Participants completed the task before and after eating a meal that matched one of the food odors, allowing us to compare perception of meal-matched and non-matched odors across fasted and sated states. We found that participants were less likely to perceive meal-matched, but not non-matched, odors as food dominant in the sated state. Moreover, functional magnetic resonance imaging (fMRI) data revealed neural changes that paralleled these behavioral effects. Namely, odor-evoked fMRI responses in olfactory/limbic brain regions were altered after the meal, such that neural patterns for meal-matched odor pairs were less discriminable and less food-like than their non-matched counterparts. Our findings demonstrate that olfactory perceptual decision-making is biased by motivational state in an odor-specific manner and highlight a potential brain mechanism underlying this adaptive behavior.

Playing Tetris Lets You Rate Odors as Less Intense.

Overweight and obesity are considered a huge problem in modern societies. Previous studies have shown that people who are regularly distracted by playing videogames or watching TV while eating are more likely to be overweight and that the number of people that are gaming worldwide is rising. Further, it has been established that both, watching TV or playing video games lead to an increased snack intake and a lower rating of perceived taste intensity. Since flavor perception is accomplished not only by the sense of taste but also the sense of smell, we investigated the influence of cognitive load created by playing a video game on odor intensity perception. The participants played a low or high difficulty version of Tetris while presented with odors of food and non-food items. A higher skin conductance response (SCR) along with a decrease in task performance verified that the higher difficulty level leads to a higher cognitive load. Our behavioral data indicates a significant decrease in intensity estimates of food odors and non-food odors during the high compared to low cognitive load condition. We conclude that odor intensity estimation is influenced by real-life cognitive tasks which might in turn lead to overeating while distracted.

Non-food odors and the duality of smell: Impact of odorant delivery pathway and labeling convention on olfactory perception

The olfactory system encompasses two perceptual pathways (orthonasal and retronasal) that activate the same receptors in the olfactory epithelium yet are thought to elicit different perceptions. Presently, a novel matching paradigm was employed using a non-food flavor set with low retronasal familiarity (honeysuckle, lavender, rose, and jasmine) to evaluate the effect of odor type on the Duality of Smell. Additionally, the influence of cognitive strategies used by subjects was assessed by manipulating the naming convention seen by the subjects: familiar (Honeysuckle, Lavender, Rose, Jasmine), unfamiliar (Inodora, Pedunculata, Beggeriana, Didymum), and generic (A, B, C, D). Subjects were presented with a reference, either in a vial (orthonasal delivery, ON) or a 2 oz. cup (retronasal delivery, RN) and instructed to match the same aroma from four unknowns, evaluated either by the same delivery route (congruent, e.g., ON-ON, RN-RN) or different route (incongruent, e.g., ON-RN, RN-ON) than the reference evaluation. All possible combinations of orthonasal and retronasal delivery for the reference and unknowns (e.g. ON-ON, RN-RN, ON-RN, RN-ON) were assessed by all subjects. Matching performance and signal detection measures indicated that, on average, subjects performed significantly better in the congruent conditions than in the incongruent conditions. These results suggest perceptual quality of aromas is route dependent and extend the Duality of Smell hypothesis to samples with low retronasal familiarity such as non-food odors. Labeling convention also had an impact on performance but, surprisingly, not in the direction anticipated. Indeed, as the information contained in the label decreased from familiar to generic reference names, performance increased. Moreover, depending on the labeling convention used, certain aromas were easier to match than others. The present research suggests odorant matching is a function of stimulus quality, cognitive strategy, and labeling convention.

Central Nervous System Processing of Floral Odor and Mother's Milk Odor in Infants.

Newborns have a functioning sense of smell at birth, which appears to be highly significant for feeding and bonding. Still, little is known about the cerebral odor processing in this age group. Studies of olfactory function relied mostly on behavioral, autonomic, and facial responses of infants. The aim of the present study was to investigate central odor processing in infants focusing on electroencephalography (EEG)-derived responses to biologically significant odors, namely a food and a non-food odor. A total of 21 term-born, healthy infants participated (11 boys and 10 girls; age range 2-9 months, mean 5.3 ± 2.2 months). Odor stimuli were presented using a computer-controlled olfactometer. Breast milk was used as food odor. Farnesol was presented as a non-food odor. In addition, odorless air was used as a control stimulus. Each stimulus was presented 30 times for 1 s with an interstimulus interval of 20 s. EEG was recorded from 9 electrodes and analyzed in the frequency domain. EEG amplitudes in the delta frequency band differed significantly after presentation of food (breast milk) odor in comparison to the control condition and the non-food odor (farnesol). These changes were observed at the frontal recording positions. The present study indicates that central odor processing differs between a food and a non-food odor in infants. Results are interpreted in terms of focused attention towards a physiologically relevant odor (breast milk), suggesting that olfactory stimuli are of specific significance in this age group.

Brain Responses to Food Odors Associated With BMI Change at 2-Year Follow-Up.

The understanding of food cue associated neural activations that predict future weight variability may guide the design of effective prevention programs and treatments for overeating and obesity. The current study investigated the association between brain response to different food odors with varied energy density and individual changes of body mass index (BMI) over 2 years. Twenty-five participants received high-fat (chocolate and peanut), low-fat (bread and peach) food odors, and a nonfood odor (rose) while the brain activation was measured using functional magnetic resonance imaging (fMRI). BMIs were calculated with participant’s self-reported body weight and height collected at the time of the fMRI scan and again at 2 years later. Regression analyses revealed significant negative correlations between BMI increase over 2 years and brain activation of the bilateral precuneus and the right posterior cingulate cortex (PCC) in response to high-fat vs. low-fat food odors. Also, brain activation of the right supplementary motor area (SMA) in response to food vs. non-food odor was negatively correlated to subsequent BMI increase over 2 years. Taken together, the current findings suggest that individual differences in neural responsivity to (high calorie) food odors in brain regions of the default mode and motor control network serve as a neural marker for future BMI change.

Insulin Resistance Is Associated with Reduced Food Odor Sensitivity across a Wide Range of Body Weights.

The worldwide obesity epidemic is a major health problem driven by the modern food environment. Recently, it has been shown that smell perception plays a key role in eating behavior and is altered in obesity. However, the underlying mechanisms of this phenomenon are not well understood yet. Since the olfactory system is closely linked to the endocrine system, we hypothesized that hormonal shifts in obesity might explain this relationship. In a within-subject, repeated-measures design, we investigated sensitivity to a food and a non-food odor in the hungry and sated state in 75 young healthy (26 normal weight, 25 overweight, and 24 obese) participants (37 women). To determine metabolic health status and hormonal reactivity in response to food intake, we assessed pre- and postprandial levels of insulin, leptin, glucose, and ghrelin. Odor sensitivity did not directly depend on body weight status/body mass index (BMI) or hunger state. However, we could establish a strong negative mediating effect of insulin resistance on the relationship between BMI/waist-hip ratio and olfactory sensitivity for the food odor. These findings indicate an impact of metabolic health status on sensitivity to food odors. Our results contribute to a better understanding of the mechanisms behind altered smell perception in obesity.

Sensitivity to sweetness correlates to elevated reward brain responses to sweet and high-fat food odors in young healthy volunteers

Taste sensitivity relates to food preferences and macronutrients intake. The current study investigated whether the neural responses to food odors varied in sensory quality (sweet or non-sweet) and their associations with macronutrient content (high- or low-fat) in young healthy participants varied in sweet taste sensitivity. Thirty-eight participants were assessed for their sensitivity to sucrose solutions using a modified “taste strip” test. They were divided into high sweetness sensitive (HS, n ​= ​15) and low sweetness sensitive (LS, n ​= ​15) groups using the median split approach. Brain responses to four food-related odors (chocolate, peach, peanut, and bread) and one non-food odor (rose) were assessed using functional magnetic resonance imaging (fMRI). Preferences for tastes and macronutrients were measured using a computer-based task. Behavioral results showed that HS group, compared to LS group, had a higher preference for carbohydrate-dominated foods and liking for sweet foods, but a lower liking for protein-dominated foods. The food odors, in comparison to non-food odors, produced greater brain-activations in the gustatory and reward regions. Compared to LS group, the HS group showed a higher level of activation in the frontal inferior operculum in response to sweet vs. savory food odors, and stronger insular activations to high-fat vs. low-fat food odors. In addition, individual sweetness sensitivity was positively associated with activation of the insula in response to chocolate odor, suggesting an overlap of neural responses to food odor with high sugar and fat content. Our findings highlight that high sensitivity to sweetness can be associated with increased preference for carbohydrate-dominated or sweet foods, and elevated brain activations to sweet or high-fat food odors in the areas related to food reward processing.

Dysfunction of the Mesolimbic Circuit to Food Odors in Women With Anorexia and Bulimia Nervosa: A fMRI Study.

Brain reward dysfunction in eating disorders has been widely reported. However, whether the neural correlates of hedonic and motivational experiences related to food cues are differentially affected in anorexia nervosa of restrictive type (ANr), bulimia nervosa (BN), and healthy control (HC) participants remains unknown. Here, 39 women (14 ANr, 13 BN, and 12 HC) underwent fMRI while smelling food or non-food odors in hunger and satiety states during liking and wanting tasks. ANr and BN patients reported less desire to eat odor-cued food and odor-cued high energy-density food (EDF), respectively. ANr patients exhibited lower ventral tegmental area (VTA) activation than BN patients to food odors when rating their desire to eat, suggesting altered incentive salience attribution to food odors. Compared with HC participants, BN patients exhibited decreased activation of the caudate nucleus to food odors in the hunger state during the wanting task. Both patient groups also showed reduced activation of the anterior ventral pallidum and insula in response to high EDF odors in the hunger state during the wanting task. These findings indicate that brain activation within the food reward-regulating circuit differentiates the three groups. ANr patients further exhibited lower activation of the precuneus than other participants, suggesting a possible role of body image distortion in ANr. Our study highlights that food odors are relevant sensory probes to gain better insight into the dysfunction of the mesolimbic and striatal circuitry involved in food reward processing in patients with EDs.

Retronasal Habituation: Characterization and Impact on Flavor Perception Using Time-Intensity

Olfactory habituation results from prolonged exposure to an odor, leading to perceptual changes defined by several characteristics. To date, human habituation research has focused on orthonasal olfaction which is perceived externally while ignoring internal routes of odor perception related to flavor. In our study, we conducted two experiments to characterize retronasal olfactory habituation and measured its impact on flavor perception. In Experiment 1, participants were presented a food odor and non-food odor retronasally, using an orally adhered strip. Each participant rated the odor intensity using a time-intensity procedure. After exposure, the participants ate a lime-flavored gummy and rated the lime flavor. In experiment 2, the same procedure was performed for a low-level lime odor, a simple (lime oil) and complex (lime oil + sucrose + citric acid) beverage as the flavor stimuli. Our results demonstrated two known principles of habituation for retronasally presented odors: (1) prolonged exposure leads to decreased perception and (2) weaker stimuli lead to more rapid habituation. Additionally, we found that the non-food odor habituated slower than the food odor; however, the participants seemed to recover simultaneously upon food and beverage consumption leading to no change in flavor perception. The findings of this study give evidence that we habituate to different odors at different rates; more specifically, we provide evidence that differentiates between odor origin and concentration. This is the first time-intensity characterization of retronasal odor habituation. Additionally, a novel method of administering retronasal odors is presented.

Altered neural responsivity to food cues in relation to food preferences, but not appetite-related hormone concentrations after RYGB-surgery

BackgroundAfter Roux-en-Y gastric bypass (RYGB) surgery, patients report a shift in food preferences away from high-energy foods. ObjectiveWe aimed to elucidate the potential mechanisms underlying this shift in food preferences by assessing changes in neural responses to food pictures and odors before and after RYGB. Additionally, we investigated whether altered neural responsivity was associated with changes in plasma endocannabinoid and ghrelin concentrations. Design19 RYGB patients (4 men; age 41 ± 10 years; BMI 41 ± 1 kg/m2 before; BMI 36 ± 1 kg/m2 after) participated in this study. Before and two months after RYGB surgery, they rated their food preferences using the Macronutrient and Taste Preference Ranking Task and BOLD fMRI responses towards pictures and odors of high-, and low-energy foods and non-food items were measured. Blood samples were taken to determine plasma endocannabinoid and ghrelin concentrations pre- and post-surgery. ResultsPatients demonstrated a shift in food preferences away from high-fat/sweet and towards low-energy/savory food products, which correlated with decreased superior parietal lobule responsivity to high-energy food odor and a reduced difference in precuneus responsivity to high-energy versus low-energy food pictures. In the anteroventral prefrontal cortex (superior frontal gyrus) the difference in deactivation towards high-energy versus non-food odors reduced. The precuneus was less deactivated in response to all cues. Plasma concentrations of anandamide were higher after surgery, while plasma concentrations of other endocannabinoids and ghrelin did not change. Alterations in appetite-related hormone concentrations did not correlate with changes in neural responsivity. ConclusionsRYGB leads to changed responsivity of the frontoparietal control network that orchestrates top-down control to high-energy food compared to low-energy food and non-food cues, rather than in reward related brain regions, in a satiated state. Together with correlations with the shift in food preference from high- to low-energy foods this indicates a possible role in new food preference formation.