Sensory-specific appetite is affected by actively smelled food odors and remains stable over time in normal-weight women

The olfactory bulb: A neuroendocrine spotlight on feeding and metabolism

Olfaction is the most ancient sense and is needed for food-seeking, danger protection, mating and survival. It is often the first sensory modality to perceive changes in the external environment, before sight, taste or sound. Odour molecules activate olfactory sensory neurons that reside on the olfactory epithelium in the nasal cavity, which transmits this odour-specific information to the olfactory bulb (OB), where it is relayed to higher brain regions involved in olfactory perception and behaviour. Besides odour processing, recent studies suggest that the OB extends its function into the regulation of food intake and energy balance. Furthermore, numerous hormone receptors associated with appetite and metabolism are expressed within the OB, suggesting a neuroendocrine role outside the hypothalamus. Olfactory cues are important to promote food preparatory behaviours and consumption, such as enhancing appetite and salivation. In addition, altered metabolism or energy state (fasting, satiety and overnutrition) can change olfactory processing and perception. Similarly, various animal models and human pathologies indicate a strong link between olfactory impairment and metabolic dysfunction. Therefore, understanding the nature of this reciprocal relationship is critical to understand how olfactory or metabolic disorders arise. This present review elaborates on the connection between olfaction, feeding behaviour and metabolism and will shed light on the neuroendocrine role of the OB as an interface between the external and internal environments. Elucidating the specific mechanisms by which olfactory signals are integrated and translated into metabolic responses holds promise for the development of targeted therapeutic strategies and interventions aimed at modulating appetite and promoting metabolic health.

The Role of the Olfactory System in Obesity and Metabolism in Humans: A Systematic Review and Meta-Analysis

Obesity, linked to chronic diseases, poses a global health challenge. While the role of the olfactory system in energy homeostasis is well-documented in rodents, its role in metabolism regulation and obesity in humans remains understudied. This review examines the interplay between olfactory function and metabolic alterations in human obesity and the effects of bariatric surgery on olfactory capabilities in humans. Adhering to PRISMA guidelines, a systematic review and meta-analysis was conducted, focusing exclusively on original human studies. From 51 articles, 14 were selected for the meta-analysis. It was found that variations in olfactory receptor genes influence the susceptibility to odors and predisposition to weight gain and poor eating habits. Bariatric surgery, particularly sleeve gastrectomy, shows significant improvements in olfactory function (SMD 2.37, 95% CI [0.96, 3.77], I = 92%, p = 0.001), especially regarding the olfactory threshold (SMD -1.65, 95% CI [-3.03, -0.27], I = 81%, p = 0.02). There is a bidirectional relationship between olfactory function and metabolism in humans. Bariatric surgery improves olfactory perception in obese patients, but it is still unclear if impacting the olfactory system directly affects eating behavior and the energy balance. However, these findings open novel avenues for future studies addressing the olfactory system as a novel target to alter systemic metabolism in humans.

Orthonasal olfactory influences on consumer food behaviour

It is often suggested in the popular press that food chains deliberately introduce enticing product aromas into (and in the immediate vicinity of) their premises in order to attract customers. However, despite the widespread use of odours in the field of sensory marketing, laboratory research suggests that their effectiveness in modulating people's food behaviours depends on a range of contextual factors. Given the evidence that has been published to date, only under a subset of conditions is there likely to be a measurable effect of the presence of ambient odours on people's food attitudes and choices. This narrative historical review summarizes the various ways in which food odours appear to bias people's food preferences (appetite) and food choices (food consumption and purchase). Emphasis is placed on those experimental studies that have been designed to investigate how the characteristics of the olfactory stimuli (e.g., the congruency between the olfactory cues and the foods, intensity and duration of exposure to odours, and taste properties of odours) modulate the effects of olfactory cues on food behaviour. The review also explores the moderating roles of individual differences, such as dietary restraint, Body Mass Index (BMI), genetic and cultural differences in odour sensitivity and perception. Ultimately, following a review of empirical studies on food-related olfaction, current approaches in scent marketing are discussed and a research agenda is proposed to help encourage further studies on the effective application of scents in promoting healthy foods.

Exploring the effects of habituation and scent in first-person 360-degree videos on consumption behavior

Although immersive virtual environments can influence food-related thoughts, emotions and behavior, the influence of repeated exposure to food cues in such environments has rarely been explored. This study seeks to understand if habituation, a decrease in one's physiological and behavioral response that results from repeated simulation, can take place while repeatedly watching 360-degrees of food being consumed. The influence of scent as an olfactory cue is further explored, based on past research on embodied cognition. In Study One (n = 42), participants who viewed 30 repetitions of someone eating an M&M ate significantly fewer M&Ms than those who viewed three repetitions. Study Two (n = 114) used a 2 (behavior: eating M&M/inserting a coin) × 2 (repetitions: 3/30) between-subjects experiment to confirm that results from Study One were due to habituation of the consumption video, finding that there were only significant differences between repetitions in the M&M condition. Finally, Study Three (n = 161) comprised a 2 (repetition: 3/30) × 2 (scent: present/absent) between-subjects experiment. Participants in the 30-repetition condition and those in the scent-present condition ate significantly fewer M&Ms respectively, but no interaction effects were found. The theoretical and practical implications of these findings are discussed.

Amygdala hyperactivation relates to eating behaviour: a potential indicator of food addiction in Prader-Willi syndrome

Prader-Willi syndrome is a rare neurodevelopmental genetic disorder characterized by various endocrine, cognitive and behavioural problems. The symptoms include an obsession for food and reduced satiety, which leads to hyperphagia and morbid obesity. Neuropsychological studies have reported that Prader-Willi patients display altered social interactions with a specific weakness in interpreting social information and responding to them, a symptom close to that observed in autism spectrum disorders. In the present case-control study, we hypothesized that brain regions associated with compulsive eating behaviour would be abnormally activated by food-related odours in Prader-Willi syndrome, as these can stimulate the appetite and induce hunger-related behaviour. We conducted a brain imaging study using the olfactory modality because odours have a high-hedonic valence and can cause stronger emotional reactions than other modalities. Further, the olfactory system is also intimately associated with the endocrine regulation of energy balance and is the most appropriate modality for studies of Prader-Willi syndrome. A total of 16 Prader-Willi participants were recruited for this study, which is a significant achievement given the low incidence rate of this rare disease. The second group of 11 control age-matched subjects also participated in the brain imaging study. In the MRI scanner, using an MRI-compatible olfactometer during 56 block sessions, we randomly presented two odours (tulip and caramel), which have different hedonic valence and a different capacity to arouse hunger-related behaviour. Our results demonstrate that Prader-Willi participants have abnormal activity in the brain reward system that regulates eating behaviour. Indeed, we found that these patients had right amygdala activity up to five times higher in response to a food odour (caramel) compared with the tulip odour. In contrast, age-matched control participants had similar activity levels in response to both odours. The amygdala activity levels were found to be associated with the severity of the hyperphagia in Prader-Willi patients. Our results provide evidence for functional alteration of the right amygdala in Prader-Willi syndrome, which is part of the brain network involved in food addiction modulated by the ghrelin and oxytocin systems, which may drive the hyperphagia. Our study provides important new insights into the functioning of emotion-related brain circuits and pathology, and it is one of the few to explore the dysfunction of the neural circuits involved in emotion and addiction in Prader-Willi syndrome. It suggests new directions for the exploration and remediation of addictive behaviours.

Smell Impairment in Stage I-II Obesity: Correlation with Biochemical Regulators and Clinical Aspects

OBJECTIVE

To evaluate the differences in olfactory sensitivity, nutritional habits, levels of modulators of feeding and smell, bioelectrical impedance analysis (BIA) measures and metabolic assays between two groups of participants with stage I and II obesity and reciprocal relationships between these parameters.

METHODS

Eighteen participants with stage I (11 female; mean age = 54.3 ± 13.1 years) and 20 participants with stage II (10 female; mean age = 54.5 ± 11.9) obesity underwent a food frequency questionnaire and Sniffin' Sticks® test battery, anthropometric parameters, and BIA measurements as well as metabolic assays (including plasma levels of leptin, insulin, ghrelin, glucose, insulin-like growth factor-1 [IGF-1] and usual laboratory parameters).

RESULTS

The stage II obesity participants demonstrated significant higher levels of insulin and leptin and lower levels of ghrelin and IGF-1, a reduction in odor identification (OI) and in total olfactory score, and an increase in visceral and total fat percentage. Among a mosaic of multiple correlations, ghrelin was found to positively correlate with OI and leptin negatively with odor discrimination.

CONCLUSION

The present study expands the notions positing the olfactory perception - and its connections with metabolic cues, foods habits and BIA measures - changes across the two most important obesity stages. This could ameliorate clinical and research deepening of obesity-related olfactory behavior with possible consequences on diagnosis, treatment and prevention of onset and development of obesity, thus opening possible future strategies involving multidisciplinary contributions.

LEVEL OF EVIDENCE

Level 3 Laryngoscope, 2022.

The Effect of Food Odor Exposure on Appetite and Nutritional Intake of Older Adults with Dementia

OBJECTIVES

Dementia can lead to decreased appetite and nutritional intake. Food odor exposure has been shown to increase appetite and nutritional intake in young healthy adults. This study investigates the effect of food odor exposure on appetite, nutritional intake and body weight of Dutch nursing home residents with dementia.

DESIGN

This was a one-armed, non-randomized, non-blinded intervention study consisting of a four-week control period followed by a twelve-week intervention period.

SETTING

Four nursing homes in the Netherlands.

PARTICIPANTS

Forty-five nursing home residents with dementia.

INTERVENTION

During the intervention period, odors were dispersed prior to the main meals.

MEASUREMENTS

General and specific appetite for sweet and savory foods was measured weekly. Nutritional intake was measured once during the control period and three times during the intervention period through a 3-day food record. Body weight was assessed at the start and end of the control period and at the start, end and halfway the intervention period. Data were analyzed with linear mixed models.

RESULTS

Small changes in general and specific appetite were observed after odor exposure. Overall energy intake did not change during the first four intervention weeks, but increased during the second and third (+118kcal/d, p=0.003 and +122kcal/d, p=0.004). Protein intake and body weight did not significantly change during the study.

CONCLUSION

In this study, no clinically relevant changes in appetite, nutritional intake and body weight were observed after food odor exposure. Future studies should assess the effect of natural food odors and/or meal-tailored odors on nutritional intake of older adults with dementia.

Food Neophobia, Odor and Taste Sensitivity, and Overall Flavor Perception in Food

Smell, which allows us to gather information about the hedonic value of an odor, is affected by many factors. This study aimed to assess the relationship among individual factors, odor sensitivity, and enjoyment, and to evaluate how overall flavor perception and liking in actual food samples are affected by odor sensitivity. A total of 749 subjects, from four different Italian regions, participated in the study. The olfactory capabilities test on four odors (anise, banana, mint, and pine), as well as PROP (6-n-prpyl-2-thiouracil) status and food neophobia were assessed. The subjects were clustered into three groups of odor sensitivity, based on the perceived intensity of anise. The liking and intensity of the overall flavor were evaluated for four chocolate puddings with increasing sweetness (C1, C2, C3, and C4). The individual variables significantly affected the perceived intensity and liking of the odors. Even if all of the odor sensitivity groups perceived the more intensely flavored samples as the C1 and C4 chocolate puddings, the high-sensitivity group scored the global flavor of all of the samples as more intense than the low-sensitivity group. The low-sensitive subjects evaluated the liking of the sweeter samples with higher scores than the moderate-sensitive subjects, whereas the high-sensitive subjects gave intermediate scores. In conclusion, odor sensitivity plays a pivotal role in the perception and liking of real food products; this has to be taken into account in the formulation of new products, suitable for particular categories with reduced olfactory abilities.

Reduced Olfactory Bulb Volume in Obesity and Its Relation to Metabolic Health Status

Smell perception plays an important role in eating behavior and might be involved in body weight gain. Since a body of literature implies that olfactory perception and function is hampered in obesity, we here investigate neuroanatomical correlates of this phenomenon. We assessed olfactory bulb (OB) volume with magnetic resonance imaging in 67 healthy participants with a body mass index (BMI) from 18.9 to 45.4 kg/m2 (mean = 28.58 ± 6.64). Moreover, we obtained psychophysiological data on olfactory ability (Sniffin' Sticks, Food associated odor test) and self-report measurements on eating behavior. Additionally, we collected parameters associated with metabolic health in obesity (waist-hip ratio, waist-height ratio, leptin levels, body fat percentage, fat mass index, insulin resistance) to investigate recently proposed mechanistic explanatory models of why olfaction may be altered in obesity. We showed that OB volume was significantly lower in participants with obesity when compared to those of normal weight. Moreover, we found weak to moderate negative correlations between OB volume and BMI and related measures of metabolic health, especially leptin, body fat percentage, waist-height ratio and insulin resistance. However, neither OB volume nor BMI were related to olfactory function in our young and healthy sample. Nevertheless, our results provide first indications that obesity is associated with brain anatomical changes in the OBs.

Changes in Salivary Proteome in Response to Bread Odour

It is widely recognized that smelling food results in a mouth-watering feeling and influences appetite. However, besides changes in volume, little is known about the effects that food odours have on the composition of saliva. The aim of the present study was to access the effects that smelling bread has on saliva proteome and to compare such effects with those of chewing and ingesting it. Besides a significant increase in saliva flow rate, together with a decrease in total protein concentration, bread odour induced changes in the proportion of different salivary proteins. The expression levels of two spots of cystatins and two spots of amylase increased due to olfactory stimulation, similar to what happened with bread mastication, suggesting that odour can allow anticipation of the type of food eaten and consequently the physiological oral changes necessary to that ingestion. An interesting finding was that bread odour increased the expression levels of several protein spots of immunoglobulin chains, which were decreased by both bread or rice mastication. This may be of clinical relevance since food olfactory stimulation of salivary immunoglobulins can be used to potentiate the oral immune function of saliva. Moreover, the effects of bread odour in the levels of salivary proteins, previously observed to be involved in oral food processing led to the hypothesis of an influence of this odour in the sensory perception of foods further ingested. Further studies are needed to elucidate this point, as well as whether the changes observed for bread odour are specific, or if different food odours lead to similar salivary proteome responses.

High confidence, yet poor knowledge of infant feeding recommendations among adults in Nova Scotia, Canada

In Canada, adherence to the national 'Nutrition for Healthy Term Infants' recommendations of infant and young child feeding (IYCF; 0-24 months) is suboptimal. While maternal knowledge of IYCF is commonly assessed, that of the general public has rarely been explored. Our objective was to assess the knowledge of, and confidence in answers to, Canadian IYCF recommendations among a diverse sample of adults in Nova Scotia, Canada. Between March and May 2018, a self-administered questionnaire examining IYCF knowledge, self-rated confidence, and sociodemographic information was conducted among Nova Scotians (≥19 years) in public locations. We surveyed 229 adults; 60% (n=134) were women. Mean (95% CI) age was 44 (41,46) years, 73% self-identified as white, 77% were born in Canada, and 69% were parents. Knowledge deficits were: age to terminate breastfeeding (18.3 (16.7,19.9) months; recommendation: ≥24 months), age to introduce solids (9.2 (8.2,10.2) months; recommendation: 6 months), vitamin D supplementation (10% correct), and optimal complementary foods (only 37% indicated iron-rich foods). Correct IYCF knowledge was lower among men, non-parents, young adults (19-29 years) and low-income adults (<$50,000/year). Mean self-rated confidence (out of 10) was high (7.2 (6.9,7.5)), and not different (p>0.05) between correct and incorrect responses for: best food for a newborn, age to terminate any breastfeeding, and age to start family meal foods. We found low knowledge of IYCF guidelines, yet high confidence in responses regardless of accuracy, among adults in Nova Scotia. General public knowledge deficits may contribute to an unsupportive culture around IYCF practices and low adherence to current recommendations.

The effect of taste and taste perception on satiation/satiety: a review

As the prevalence of being overweight and obesity has increased worldwide, there is an increasing concern about satiation/satiety that can be achieved by eating. The ability of an individual to perceive tastes in the mouth is believed to be one of the many factors that influence food intake; the taste may affect appetite regulation and energy intake, playing an important role in promoting satiation/satiety. Satiation/satiety is actually induced by food and may be related to physiological and psychological factors such as several basic tastes, the exposure time of the taste and the cognition of different groups and individuals. This paper reviews the mechanism by which taste regulates satiation/satiety and demonstrates how taste and the taste perception of food prompt the brain to send satiation/satiety signals. Existing problems in taste and satiation/satiety and the prospective application of related research in the food industry are addressed, providing a scientific basis and theoretical guidance for the development and utilization of satiation/satiety from the perspective of taste.

Sensory Profile of Adults with Reduced Food Intake and the Potential Roles of Nutrition and Physical Activity Interventions

The sensory profile, referring to sight, smell, taste, hearing, and touch, plays an essential role in optimizing the habitual intake of energy and macronutrients. However, specific populations, such as older adults, are known to have impaired energy intake. In this paper, the relevance of sensory impairments in this older population is described, and the extent to which nutritional and physical activity interventions can modulate these sensory responses when food intake is insufficient is explored. With aging, all senses deteriorate, and in most cases, such deteriorations diminish the nutritional response. The only exception is sight, for which both positive and negative impacts on nutritional response have been reported. From a prevention perspective, nutritional interventions have been understudied, and to date, only hearing is known to be positively affected by a good nutritional profile. In comparison, physical activity has been more frequently studied in this context, and is linked to an improved preservation of 4 senses. Regarding treatment, very few studies have directly targeted sensory training, and the focus of research has tended to be on nutrition and physical activity intervention. Sensory training, and nutritional and physical activity treatments all have beneficial effects on the senses. In the future, researchers should focus on exploring gaps in the literature specifically concerning prevention, treatment, and sensory response to understand how to improve the efficacy of current approaches. In order to maintain sensory acuity and recover from sensory impairment, the current state of knowledge supports the importance of improving nutritional habits as well as physical activity early on in life. A combined approach, linking a detailed lifestyle profile with the assessment of numerous senses and one or more interventional approaches (nutrition, physical activity, sensory training, etc.), would be required to identify effective strategies to improve the nutritional state of older individuals.

Do children with a high level of eating motivation consume less when foods are partitioned?

Eating behaviors, especially the control of intake, are modulated by both internal and external factors. The objective of our study was to examine the effect of the interaction between eating motivation (as an internal factor) and food partition (as an external factor) on chocolate intake in children, with the hypothesis, based on the paradigm of motivated perception, that the effect of partition, i.e. reduced intake, is higher for children with a high level of eating motivation than for other children. A mixed model design was used in which 80 children aged 8-11 yrs. were offered, in their natural setting, two standardized afternoon snacks that included, among other things, 100 g of chocolate presented once as a whole (one bar) and once segmented (six pieces). The amount of chocolate eaten was weighed and compared between conditions (Bar vs Pieces). Children completed questionnaires in order to assess two of their eating motivational features (appetite arousal, chocolate specific appetite). Results indicated no effect of Partition: children ate the same quantity of chocolate in the two conditions (Bar or Pieces). Only chocolate specific appetite was associated with the amount of chocolate eaten, with children with a higher level eating more than other children (+13 g). Contrary to adults, children are not influenced by the "many is more effect". Methodological and developmental interpretations were suggested, linked to the size of the portion, the network of attention and the sensibility to the external cues underlying the control of intake.

Ambient Odor Exposure Affects Food Intake and Sensory Specific Appetite in Obese Women

Food odors are important in food perception not only during consumption, but also in anticipation of food. Even though it is well established that smell is involved in eating behavior, its role in affecting actual food consumption is still unclear, especially in morbidly obese subjects, who are reported to be more affected by sensory cues than lean subjects. The aim of the present study was to investigate the influence of ambient odor exposure on ad libitum food intake and on sensory specific appetite in obese women. Thirty obese women (BMI: 34.9 ± 0.8 kg m^-2; age: 50.8 ± 1.8) attended two sessions in which they were exposed to a bread odor dispersed, in a detectable but mild concentration, in the test room (“scented” condition) and to a control condition (“unscented” condition). Participants filled out a questionnaire on general appetite before entering the test room and completed a sensory specific appetite questionnaire (including 12 specific products) about 10 min after entering the test room. After approximately 15 min of exposure, the ad libitum intake of a low energy dense food product (vegetable soup) was measured. The “scented” condition significantly (p < 0.01) increased the amount of soup eaten compared to the “unscented” condition (466.4 ± 33.1 g; 368.9 ± 33.2 g, respectively). Moreover, the odor exposure induced sensory specific appetite for congruent food products in term of taste and energy density, as well as a significant increase in general appetite scores (p < 0.001). In conclusion, ambient odor exposure to a food odor affected the intake of a low energy food in obese women and stimulated appetite for congruent products. This could have important implications for influencing energy intake of individuals.

Effect of exposure to similar flavours in sensory specific satiety: Implications for eating behaviour

Sensory-specific satiety (SSS) refers to a decline in pleasantness of eaten foods in comparison to other non-ingested meals. Although SSS is specific to the eaten food, it can also generalize to other meals that share similar properties to the satiated food. It is possible that this phenomenon could become more specific after extensive experience, as repeated exposure to an assortment of similar food could cause perceptual learning (i.e. an increase in the distinctiveness of each specific item). This in turn would reduce generalization from the consumed food to other similar products, so they will be more readily consumed. To assess this hypothesis, two experiments were carried out using rats as experimental subjects and flavoured solutions as stimuli. In Experiment 1 our main goal was to find the basic SSS effect with two different solutions. As expected, the results showed that rats tended to consume a higher amount of non-sated solutions in comparison to sated ones. Experiment 2 evaluated how repeated exposure to two similar solutions affected generalization of the SSS. Results showed that rats that did not have extensive exposure to the flavoured solutions showed no preference for the non-sated drink. However, rats that had repeated exposure to the flavours showed SSS. The results suggest that easy and continuous access to a high variety of similar unhealthy foods might have long-term effects on food consumption, and highlight a potential mechanism linking obesogenic environments with dietary habits.

Developing Healthy Food Preferences in Preschool Children Through Taste Exposure, Sensory Learning, and Nutrition Education

PURPOSE OF REVIEW

The present review was undertaken in order to summarize and evaluate recent research investigating taste exposure, sensory learning, and nutrition education interventions for promoting vegetable intake in preschool children.

RECENT FINDINGS

Overall, taste exposure interventions yielded the best outcomes for increasing vegetable intake in early childhood. Evidence from sensory learning strategies such as visual exposure and experiential learning also show some success. While nutrition education remains the most common approach used in preschool settings, additional elements are needed to strengthen the educational program for increasing vegetable intake. There is a substantial gap in the evidence base to promote vegetable intake in food fussy children. The present review reveals the relative importance of different intervention strategies for promoting vegetable intake. To strengthen intervention effects for improving vegetable intake in preschool children, future research could consider integrating taste exposure and sensory learning strategies with nutrition education within the preschool curriculum.

Placing of aroma compounds by food sales promotion in chosen services business

There are several ways to get higher sale involving human senses too. One of the options is a security of stimulating atmosphere of sale/ business environment. In addition to equipment, design and staff, the lighting, sound (noise), and last ones but not least smell, respectively air quality significantly take part on that. Aroma is the element that inherently belongs to the visual merchandising tools. It can influence not only emotions, memory, but total customers´ satisfaction and preferences as well as spending time in that place. In this context, it is important to find right compromise when choosing the aromatic compounds for various products, in the process of their application (intensity, process of aromatization) and security of sufficient air quality, because everybody perceives the odours with different sensitivity. Properly chosen smell and factors of air quality bring for business operators (services trades) many advantages; from staff, who more relax and friendly behave to the guests until making of various associations and stimulations of customers, who spend time inside of service. Fragrance or air quality looks like based on of present researches as the most important factor directly on point-of-sale, while aroma acquires the importance in case of memory too. On the one side, the thinks, which are seen or heard by customers, could be memorized by them few days or weeks, so on the second side, the thinks which are smelled, could be memorized by guests many decades. Except this, the Scientifics studies show, that over 75 % of all emotions are generated based on scent´ perception. The main aim of this paper is a research, how aroma influences customer purchasing decision (preferences) in chosen service provider through the tracking of daily sales of baked baguettes (Paninis) with using of aroma equipment; Aroma Dispenser.

Food Odours Direct Specific Appetite

Olfactory food cues were found to increase appetite for products similar in taste. We aimed to replicate this phenomenon for taste (sweet/savoury), determine whether it extends to energy density (high/low) as well, and uncover whether this effect is modulated by hunger state. Twenty-nine healthy-weight females smelled four odours differing in the energy density and taste they signalled, one non-food odour, and one odourless solution (control), in random order, for three minutes each. Appetite for 15 food products was rated in the following two minutes. Mixed model analyses revealed that exposure to an odour signalling a specific taste (respectively sweet, savoury) led to a greater appetite for congruent food products (sweet/savoury) compared to incongruent food products (savoury p < 0.001; sweet p < 0.001) or neutral food products (p = 0.02; p = 0.003). A similar pattern was present for the energy-density category (respectively high-energy dense, low-energy dense) signalled by the odours (low-energy products p < 0.001; high-energy products p = 0.008). Hunger state did not have a significant impact on sensory-specific appetite. These results suggest that exposure to food odours increases appetite for congruent products, in terms of both taste and energy density, irrespective of hunger state. We speculate that food odours steer towards intake of products with a congruent macronutrient composition.

Food Preference and Appetite after Switching between Sweet and Savoury Odours in Women

Background

Exposure to food odours increases the appetite for congruent foods and decreases the appetite for incongruent foods. However, the effect of exposure to a variety of food odours, as often occurs in daily life, is unknown.

Objective

Investigate how switching between sweet and savoury odours affects the appetite for sweet and savoury products.

Design

Thirty women (age: 18-45y; BMI: 18.5-25kg/m²) intensely smelled the contents of cups filled with banana, meat or water (no-odour) in a within-subject design with four combinations: no-odour/banana, no-odour/meat, meat/banana and banana/meat. Participants received one combination per test day. In each combination, two cups with different fillings were smelled for five minutes after each other. Treatment order was balanced as much as possible. The effects of previous exposure and current odour on the appetite for (in)congruent sweet and savoury products, and odour pleasantness were analysed. A change from meat to banana odour or banana to meat odour was referred to as switch, whereas a change from no-odour to meat odour or no-odour to banana odour was no-switch.

Results

The current odour (P<0.001), as opposed to the previous exposure (P = 0.71), determined the appetite for (in)congruent sweet and savoury products, already one minute after a switch between sweet and savoury odours. The pleasantness of the odour decreased during odour exposure (P = 0.005).

Conclusions

After a switch, the appetite for specific products quickly adjusted to the new odour and followed the typical pattern as found during odour exposure in previous studies. Interestingly, the appetite for the smelled food remained elevated during odour exposure, known as sensory-specific appetite, whereas the pleasantness of the odour decreased over time, previously termed olfactory sensory-specific satiety. This seeming contradiction may result from different mechanisms underlying the odour-induced anticipation of food intake versus the decrease in hedonic value during prolonged sensory stimulation.