The effect of social norms on vegetarian choices is moderated by intentions to follow a vegetarian diet in the future: Evidence from a laboratory and field study.

Social norms could be a tool in dietary transition toward more sustainable diets, but the results of social norms interventions aimed at encouraging the selection of plant-based foods to date have been inconsistent. One reason for this might be because there are important moderating factors that have yet to be investigated. Here we examine social modeling of vegetarian food choices and test whether modeling is dependent upon individual intentions to follow a vegetarian diet in the future in two different settings. In a laboratory study of 37 women, participants with low intentions to become a vegetarian consumed fewer plant-based foods in the presence of a vegetarian confederate, compared to eating alone. In an observational study of 1,037 patrons of a workplace restaurant, participants with a higher score of on vegetarian intentions had a greater likelihood of taking a vegetarian main course or starter, and a vegetarian social norm was associated with a greater likelihood of a vegetarian choice for the main course but not for the starter. These data suggest that participants with low intentions to follow a vegetarian diet may exhibit reactance against an explicit vegetarian norm in an unfamiliar context (as in Study 1) but that general norm following regardless of dietary intentions be more likely when it is conveyed implicitly in a familiar context (as in Study 2).

Principles and Validations of an Artificial Intelligence-Based Recommender System Suggesting Acceptable Food Changes.

BACKGROUND: Along with the popularity of smartphones, artificial intelligence-based personalized suggestions can be seen as promising ways to change eating habits toward more desirable diets. OBJECTIVES: Two issues raised by such technologies were addressed in this study. The first hypothesis tested is a recommender system based on automatically learning simple association rules between dishes of the same meal that would make it possible to identify plausible substitutions for the consumer. The second hypothesis tested is that for an identical set of dietary-swaps suggestions, the more the user is-or thinks to be-involved in the process of identifying the suggestion, the higher is their probability of accepting the suggestion. METHODS: Three studies are presented in this article, first, we present the principles of an algorithm to mine plausible substitutions from a large food consumption database. Second, we evaluate the plausibility of these automatically mined suggestions through the results of online tests conducted for a group of 255 adult participants. Afterward, we investigated the persuasiveness of 3 suggestion methods of such recommendations in a population of 27 healthy adult volunteers through a custom designed smartphone application. RESULTS: The results firstly indicated that a method based on automatic learning of substitution rules between foods performed relatively well identifying plausible swaps suggestions. Regarding the form that should be used to suggest, we found that when users are involved in selecting the most appropriate recommendation for them, the resulting suggestions were more accepted (OR = 3.168; P < 0.0004). CONCLUSIONS: This work indicates that food recommendation algorithms can gain efficiency by taking into account the consumption context and user engagement in the recommendation process. Further research is warranted to identify nutritionally relevant suggestions.

Rats chirp with their mouth full: During an experimental meal, adult male Wistar rats emitted flat ultrasonic vocalisations upon feeding.

Rats produce ultrasonic vocalisation (USVs) that are classified into different types, based on their average frequency. In pups 40 kHz USVs are produced upon social isolation, and in adults USVs can be associated with affective states and specific behavioural patterns (i.e., appetitive 50 kHz vocalisations of frequency range 30-100 kHz, or aversive 20 kHz vocalisations of frequency range 18-30 kHz). Generally, USVs of frequency around 50 kHz are linked to activation of brain reward pathways, during anticipation or experience of rewarding stimuli. Previous studies have described several subtypes of 50 kHz USVs, according to their acoustic properties. We asked whether USV production might be relevant to feeding behaviour. We recorded USVs from 14-week old adult rats during the satisfaction of a physiological need: refeeding following mild food deprivation (17 h overnight fast). We analysed a 10 min consummatory phase, preceded by a 10 min anticipatory phase, as a control for the experimental meal. Following identification of USV subtypes, we applied frequentist and Bayesian (Monte Carlo shuffling) statistical analyses to investigate the relationship between USV emission and rat behaviour. We found that it was not total USV quantity that varied in response to food consumption, but the subtype of USV produced. Most importantly we found that rats who feed tend to produce flat USVs of a frequency around 40 kHz. Beyond the previous reports of circumstantial association feeding-flat USVs, our observation directly correlate vocalisation and ingestive behaviour. Our study highlights that, in addition to quantification of the production rate, study of USV subtypes might inform us further on rat consummatory behaviour. Since this vocalisation behaviour can have a communicative purpose, those findings also illustrate nutrition studies might benefit from considering the possible social dimension of feeding behaviour.

Dopamine Modulates the Processing of Food Odour in the Ventral Striatum.

Food odour is a potent stimulus of food intake. Odour coding in the brain occurs in synergy or competition with other sensory information and internal signals. For eliciting feeding behaviour, food odour coding has to gain signification through enrichment with additional labelling in the brain. Since the ventral striatum, at the crossroads of olfactory and reward pathways, receives a rich dopaminergic innervation, we hypothesized that dopamine plays a role in food odour information processing in the ventral striatum. Using single neurones recordings in anesthetised rats, we show that some ventral striatum neurones respond to food odour. This neuronal network displays a variety of responses (excitation, inhibition, rhythmic activity in phase with respiration). The localization of recorded neurones in a 3-dimensional brain model suggests the spatial segregation of this food-odour responsive population. Using local field potentials recordings, we found that the neural population response to food odour was characterized by an increase of power in the beta-band frequency. This response was modulated by dopamine, as evidenced by its depression following administration of the dopaminergic D1 and D2 antagonists SCH23390 and raclopride. Our results suggest that dopamine improves food odour processing in the ventral striatum.

Associations between Perceived Social Eating Norms and Initiation and Maintenance of Changes in Dietary Habits during the First COVID-19 Lockdown in France.

Changes in dietary habits of the French population have been reported during the national lockdown that was enforced due to the COVID-19 pandemic. This study investigated whether perceived social eating norms were associated with the initiation and maintenance of dietary changes that took place as a result of lockdown. An online study collected information on (1) changes in consumption implemented during the lockdown and the maintenance of these changes, and (2) perceptions about changes in consumption implemented during lockdown by household members, relatives out of home, and the general population. The changes in consumption were classified as foods to increase or to decrease according to French national recommendations. The perception of changes to dietary habits by household members and relatives out of home was related to the changes made by individuals for each of the food categories (all p < 0.05) but not to the perception of changes made the general population. Increased consumption of foods to increase was more likely to be maintained when there was a positive perception of the changes made by household members (p = 0.03). These results highlight the influence of the perception of social eating norms, especially by household members and relatives, on the implementation of dietary changes during lockdown and suggest that social eating norms can have a lasting influence.

Diet Protein Content and Individual Phenotype Affect Food Intake and Protein Appetence in Rats.

BACKGROUND: A low-protein diet can induce compensatory intake of excess energy. This must be better evaluated to anticipate the obesogenic risk that may result from the dietary recommendations for reducing animal protein consumption. OBJECTIVES: We aimed to further characterize the behavioral and physiological responses to a reduction in dietary protein and to identify the determinants of protein appetite. METHODS: Thirty-two male Wistar rats [4 wk old, (mean ± SEM) 135 ± 32 g body weight] were fed a low-protein (LP; 6% energy value) or normal-protein (NP; 20%) diet for 8 wk. Food intake and body mass were measured during the entire intervention. During self-selection sessions after 4 wk of experimental diets, we evaluated rat food preference between LP, NP, or high-protein (HP; 55%) pellets. At the end of the experiment, we assessed their hedonic response [ultrasonic vocalizations (USVs)] and c-Fos neuronal activation in the olfactory tubercle and nucleus accumbens (NAcc) associated with an LP or HP meal. RESULTS: Rats fed an LP diet had greater food intake (24%), body weight (5%), and visceral adiposity (30%) than NP rats. All LP rats and half of the NP rats showed a nearly exclusive preference for HP pellets during self-selection sessions, whereas the other half of the NP rats showed no preference. This suggests that the appetite for proteins is driven not only by a low protein status but also by individual traits in NP rats. LP or HP meal induced similar USV emission and similar neuronal activation in the NAcc in feed-deprived LP and NP rats, showing no specific response linked to protein appetite. CONCLUSIONS: Protein appetite in rats is driven by low protein status or individual preferences in rats receiving adequate protein amounts. This must be considered and further analyzed, in the context of current recommendations for protein intake reduction.

Local Foods Can Increase Adequacy of Nutrients Other than Iron in Young Urban Egyptian Women: Results from Diet Modeling Analyses.

BACKGROUND: Nutrition transition and recent changes in lifestyle in Middle Eastern countries have resulted in the double burden of malnutrition. In Egypt, 88% of urban women are overweight or obese and 50% are iron deficient. Their energy, sugar, and sodium intakes are excessive, while intakes of iron, vitamin D, and folate are insufficient. OBJECTIVE: This study aimed to formulate dietary advice based on locally consumed and affordable foods and determine the need for fortified products to meet the nutrient requirements of urban Egyptian women. METHODS: Food intakes were assessed using a 4-d food diary collected from 130 urban Egyptian women aged 19-30 y. Food prices were collected from modern and traditional markets to calculate diet cost. Population-based linear and goal programming analyses (Optifood tool) were used to identify "limiting nutrients" and to assess whether locally consumed foods (i.e., consumed by >5% of women) could theoretically improve nutrient adequacy at an affordable cost (i.e., less than or equal to the mean diet cost), while meeting recommendations for SFAs, sugars, and sodium. The potential of hypothetical fortified foods for improving intakes of micronutrients was also assessed. RESULTS: Iron was the most limiting nutrient. Daily consumption of fruits, vegetables, milk or yogurt, meat/fish/eggs, and tahini (sesame paste) were likely to improve nutrient adequacy for 11 out of 12 micronutrients modeled. Among fortified foods tested, iron-fortified rice, milk, water, bread, or yogurt increased the minimized iron content of the modeled diet from 40% to >60% of the iron recommendation. CONCLUSIONS: A set of dietary advice based on locally consumed foods, if put into practice, can theoretically meet requirements for most nutrients, except for iron for which adequacy is harder to achieve without fortified products. The acceptability of the dietary changes modeled needs evaluation before promoting them to young Egyptian women.

Social modeling of food choices in real life conditions concerns specific food categories.

The social context of eating has a profound effect on consumption choices. Social modeling, that involves using others' behavior as a guide for appropriate consumption, has been well documented for food intake, but less is known about social modeling of food choices. Moreover, social modeling has mainly been studied in laboratory settings. We conducted an observational study in a self-service canteen to examine whether the food choices of an individual were influenced by the choice of the person ahead in the queue. We recorded food choices of 546 individuals (333 men and 211 women) and those of the person in front of them in the queue along a linear buffet. Starters were sub-categorized into salads, mixed starters (e.g. avocado shrimp mayonnaise), and cold meat starters, and desserts were sub-categorized into fruits, dairy products and pastries. There was a significantly higher probability of taking a starter in general (OR = 1.65, IC = 1.06-2.57, p = 0.03), a salad (OR = 1.78, CI = 1.08-2.93, p = 0.02), a mixed starter (OR = 2.98, CI = 1.42-6.05, p < 0.01), but not a cold meat, if the person ahead in the queue also took one compared to when the person ahead did not take one. No significant modelling was found for desserts which may be because almost all participants took a dessert. These results highlight that social modeling influences food choices, and that this phenomenon can be observed in a real life setting. These data also suggest that some food categories, such as starters, could be more susceptible to social modeling than are others. Finally, we observed modeling both between familiar and unfamiliar participants, which suggests that social norms could be used to promote healthier eating in a range of settings including friendship groups.

Perinatal exposure of rats to a maternal diet with varying protein quantity and quality affects the risk of overweight in female adult offspring.

The maternal protein diet during the perinatal period can program the health of adult offspring. This study in rats evaluated the effects of protein quantity and quality in the maternal diet during gestation and lactation on weight and adiposity in female offspring. Six groups of dams were fed a high-protein (HP; 47% protein) or normal-protein (NP; 19% protein) isocaloric diet during gestation (G) using either cow's milk (M), pea (P) or turkey (T) proteins. During lactation, all dams received the NP diet (protein source unchanged). From postnatal day (PND) 28 until PND70, female pups (n=8) from the dam milk groups were exposed to either an NP milk diet (NPMW) or to dietary self-selection (DSS). All other pups were only exposed to DSS. The DSS design was a choice between five food cups containing HPM, HPP, HPT, carbohydrates or lipids. The weights and food intakes of the animals were recorded throughout the study, and samples from offspring were collected on PND70. During the lactation and postweaning periods, body weight was lower in the pea and turkey groups (NPG and HPG) versus the milk group (P<.0001). DSS groups increased their total energy and fat intakes compared to the NPMW group (P<.0001). In all HPG groups, total adipose tissue was increased (P=.03) associated with higher fasting plasma leptin (P<.05). These results suggest that the maternal protein source impacted offspring body weight and that protein excess during gestation, irrespective of its source, increased the risk of adiposity development in female adult offspring.

Urban Egyptian Women Aged 19-30 Years Display Nutrition Transition-Like Dietary Patterns, with High Energy and Sodium Intakes, and Insufficient Iron, Vitamin D, and Folate Intakes.

BACKGROUND: Recent changes in Egyptian dietary habits can be attributed to more urban and sedentary lifestyles and to alterations in the dietary and economic context. The mean BMI of Egyptian women is one of the highest worldwide, and 50% have iron deficiency. OBJECTIVE: The aim was to quantify food and nutrient intakes of urban Egyptian women and conduct a detailed analysis of micronutrients commonly consumed in inadequate amounts, such as iron, vitamin D, and folate. METHODS: Urban Egyptian women aged 19-30 y (n = 130) were recruited during 2016-2017. Energy needs were estimated using the Henry equation, assuming a low physical activity level (1.4). Dietary intakes and iron bioavailability were estimated from a 4-d food diary. Macronutrient intakes were compared with WHO/FAO population goals and micronutrient intakes with Egyptian recommendations. Iron needs were determined for each subject. RESULTS: The mean BMI (kg/m2) was 27.9 ± 4.9. The mean total energy intake (TEI; 2389 ± 715 kcal/d) was significantly higher than needs (2135 ± 237 kcal/d; P = 0.00018). Total fat (33%TEI) and SFA (11%TEI) intakes were slightly higher than population goals (15-30%TEI and <10%TEI, respectively). Diets provided 18 ± 8 g/d of fiber, 98 ± 54 g/d of total sugars, and nearly twice the recommended sodium intake (intake: 2787 ± 1065 mg/d; recommendation: <1500 mg/d). Estimated dietary iron bioavailability was low (9.2% ± 1.6%), and 79% of women consumed less iron than the average requirement (17.5 ± 7 mg/d). Overall, 82% and 80% of women consumed less vitamin D and folate, respectively, than recommended. CONCLUSIONS: Egyptian women aged 19-30 y have high intakes of energy and sodium, whereas iron, vitamin D, and folate intakes are insufficient, with only low concentrations of bioavailable iron. These results call for further investigation into measures that would improve this population's diet quality.

Protein Status Modulates an Appetite for Protein To Maintain a Balanced Nutritional State-A Perspective View.

Protein sufficiency is tightly controlled through different sensing and signaling processes that modulate and adapt protein and energy metabolism and feeding behavior to reach and maintain a well-balanced protein status. High-protein diets, often discussed in the context of body weight management, usually activate anorexigenic pathways, leading to higher satiety, decreased food and energy intake, and decreased body weight and adiposity. Diets marginally low in protein (3-8% energy) or marginally deficient in some indispensable amino acid more often activate orexigenic pathways, with higher appetite and a specific appetite for protein, a response that leads to an increase in protein intake to partially compensate for the deficit in protein and amino acid. Diets severely deficient in protein (2-3% energy as protein) usually depress food intake and induce lower weight and lower fat mass and lean tissues that characterize a status of protein deficiency. The control of protein sufficiency involves various peripheral and central signals, including modulation of both metabolic pathways at the periphery as well as central pathways of the control of food and protein intake, including a reward-driven specific sensitivity to the protein content of foods.

Self-declared attitudes and beliefs regarding protein sources are a good prediction of the degree of transition to a low-meat diet in France.

Meat consumption in Western countries is declining and, while the proportion of strict vegetarians remains low, intermediate diets such as flexitarianism have been developing in recent years. Our objectives were to identify the different levels of transition towards low-meat diets, characterize how these diets differ in terms of food intake, and identify whether attitudes and beliefs can explain these degrees of transition. In a representative survey of the French adult population conducted in 2018 (n = 2055), participants declared whether they followed a particular diet and completed a food frequency questionnaire on 29 food sources of protein and a questionnaire on their attitudes and beliefs regarding protein sources. We identified four dietary types based on these declarative data: vegetarians, flexitarians, pro-flexitarians and omnivores. The theory of planned behavior was used to predict meat intake and intentions to reduce meat intake. The sample contained 2.5% vegetarians, 6.3% flexitarians, 18.2% pro-flexitarians and 72.9% omnivores. The diet groups displayed specific dietary profiles and attitudinal scores. Compared with omnivores, pro-flexitarians consumed less red meat, more vegetables and legumes and were much more in agreement about the environmental impacts of meat. Compared with pro-flexitarians, flexitarians consumed less red meat and processed meat, and agreed much more about the health impacts of meat. Finally, versus flexitarians, vegetarians consumed almost no meat but far more legumes, nuts and seeds, and were much more sensitive to animal welfare issues. Attitudes, social norms and perceived behavioral control (PBC) predicted intentions to reduce meat consumption but attitude was the most important predictor. Intentions and PBC were both predictive of meat consumption. The dietary type related to the level of meat intake could be predicted by self-declared attitudes and beliefs regarding protein sources.

The Willingness to Modify Portion Sizes or Eat New Protein Foods Largely Depends on the Dietary Pattern of Protein Intake.

Promoting a more balanced animal/plant dietary protein ratio by changing portion sizes or introducing new foods is a promising means to improve diet quality, but little is known about the willingness of individuals to adopt such changes. Our objective was to assess the willingness to adopt dietary changes by these means. In a French cross-sectional study in 2018 (n = 2055), we analyzed the association between the willingness to eat smaller or larger portions or to introduce non-consumed protein foods and the current dietary patterns of individuals and their socio-demographic characteristics. These modifications had previously been identified as improving the nutrient adequacy of diets. Participants were more willing to eat smaller portion sizes than to introduce new foods and to eat larger portion sizes. The willingness for any modification varied depending on the food groups concerned. Participants were also more willing to eat larger portions and less willing to eat smaller portions when they were the most frequent consumers of the foods concerned. Participants were more willing to eat a new food if it was consumed in large quantities by individuals with a similar dietary pattern. This study underlines the importance of accounting for individual food habits when issuing nutritional recommendations.

Protein status modulates the rewarding value of foods and meals to maintain an adequate protein intake.

Proteins are dietary components that contribute to nutritional needs of the body through the provision of nitrogen and amino acids. Protein status is tightly and continuously controlled to prevent or counteract protein deficiency and to maintain or restore an adequate protein status. Animals learn to detect and avoid diets deficient or devoid in protein or in at least one indispensable amino acid and when given a choice reject these diets. Diets restricted marginally in protein or in one or more amino acids more often induce hyperphagia, interpreted as an attempt to increase protein or amino acid intake and to meet the need for protein and amino acids. The increase in energy intake induced by a low protein diet is compensated for by an increased energy expenditure that restrains the gain in adiposity. The status of protein and/or amino acid insufficiency induced by protein or amino acid restricted diets is characterized by a profile of peripheral and central signals that contribute to modulate peripheral metabolic adaptations and central pathways involved in the control of feeding behaviour. These processes impact on the motivation for food and food choice, with an appetite for protein and/or for the limiting amino acid (s) associated with a reward driven sensitivity to protein and amino acid content of food and diets, which leads to restore or maintain an adequate protein status. In contrast to a protein-restricted diet, high-protein diets are usually reported to decrease food intake in both animals and humans, at least for a transient period, in relation to a reported satiating effect of proteins through activation of anorexigenic pathways.

Maternal High-Protein Diet during Pregnancy Modifies Rat Offspring Body Weight and Insulin Signalling but Not Macronutrient Preference in Adulthood.

Diet of mothers during gestation may impact offspring phenotype. This study evaluated the consequences of a maternal High-Protein (HP) diet during gestation on food preferences and phenotypic characteristics in adult rat offspring. Dams were fed a HP or a Normal-Protein (NP) isocaloric diet during gestation only. Weaned female pups were divided into 3 diet groups: NP control or one of two dietary self-selection (DSS) conditions. In DSS1, offspring had a free choice between proteins (100%) or a mix of carbohydrates (88%) and lipids (12%). In DSS2, the choice was between proteins (100%), carbohydrate (100%) or lipids (100%). DSS2 groups consumed more of their energy from protein and lipids, with a decreased carbohydrate intake (p < 0.0001) compared to NP groups, regardless of the maternal diet. Offspring from HP gestation dams fed the DSS2 diet (HPDSS2) had a 41.2% increase of total adiposity compared to NPDSS2 (p < 0.03). Liver Insulin receptor and Insulin substrate receptor 1 expression was decreased in offspring from HP compared to NP gestation dams. These results showed the specific effects of DSS and maternal diet and data suggested that adult, female offspring exposed to a maternal HP diet during foetal life were more prone to adiposity development, in response to postweaning food conditions.

Providing a Smart Healthy Diet for the Low-Income Population: Qualitative Study on the Usage and Perception of a Designed Cooking App.

BACKGROUND: Health behaviors among low-income groups have become a major issue in the context of increasing social inequalities. The low-income population is less likely to be receptive to nutritional recommendations, but providing cooking advice could be more effective. In this domain, taking advantage of digital devices can be a bonus with its own challenges. OBJECTIVE: The aim of this study was to develop and deploy NutCracker, a social network-based cooking app for low-income population, including cooking tips and nutritional advices, aiming at creating small online communities. We further determined the usefulness, perceptions, barriers, and motivators to use NutCracker. METHODS: The smartphone app, designed jointly with beneficiaries of the social emergency services, was implemented in a disadvantaged neighborhood of Magny, (Paris region, France). Once the app became available, 28 subjects, living in the neighborhood, tested the app for a 6-month period. Logs to the app and usages were collected by the software. In total, 12 in-depth, semistructured interviews were conducted among the users and the social workers to analyze their uses and perceptions of the app relative to their interest in cooking, cooking skills, socioeconomic constraints, and social integration. These interviews were compared with 21 supplementary interviews conducted among low-income individuals in the general population. RESULTS: NutCracker was developed as a social network-based app, and it includes cooking tips, nutritional advice, and Web-based quizzes. We identified barriers to uses (especially technical barriers, lack of knowledge in the field of new technologies and written comprehension, and search for real contacts) and motivators (in particular, good social integration, previous use of social networks, and help of children as intermediaries). Cooking skills were both a barrier and a lever. CONCLUSIONS: Targeting the low-income groups through a cooking app to promote healthier behaviors offers many advantages but has not been fully explored. However, the barriers in low-income milieu remain high, especially among the less socially integrated strata. Lessons from this intervention allow us to identify barriers and possible levers to improve nutrition promotion and awareness in deprived areas, especially in the time of social crisis.

Differences in BOLD responses in brain reward network reflect the tendency to assimilate a surprising flavor stimulus to an expected stimulus.

External information can modify the subjective value of a tasted stimulus, but little is known about neural mechanisms underlying these behavioral modifications. This study used flavored drinks to produce variable degrees of discrepancy between expected and received flavor. During a learning session, 43 healthy young men learned 4 symbol-flavor associations. In a separate session, associations were presented again during an fMRI scan, but half of the trials introduced discrepancy with previously learned associations. Liking ratings of drinks were collected and were analyzed using a linear model to define the degree to which discrepant symbols affected liking ratings of the subjects during the fMRI session. Based on these results, a GLM analysis of fMRI data was conducted to determine neural correlates of observed behavior. Groups of subjects were composed based on their behavior in response to discrepant symbols, and comparison of brain activity between groups showed that activation in the PCC and the caudate nucleus was more potent in those subjects in which liking was not affected by discrepant symbols. These activations were not found in subjects who assimilated unexpected flavors to flavors preceeded by discrepant symbols. Instead, these subjects showed differences in the activity in the parietal operculum. The activity of reward network appears to be related to assimilation of received flavor to expected flavor in response to symbol-flavor discrepancy.

The Protein Status of Rats Affects the Rewarding Value of Meals Due to their Protein Content.

Background: Protein status is controlled by the brain, which modulates feeding behavior to prevent protein deficiency. Objective: This study tested in rats whether protein status modulates feeding behavior through brain reward pathways. Methods: Experiments were conducted in male Wistar rats (mean ± SD weight; 230 ± 16 g). In experiment 1, rats adapted for 2 wk to a low-protein (LP; 6% of energy) or a normal-protein (NP; 14% of energy) diet were offered a choice between 3 cups containing high-protein (HP; 50% of energy), NP, or LP feed; their intake was measured for 24 h. In 2 other experiments, the rats were adapted for 2 wk to NP and either HP or LP diets and received, after overnight feed deprivation, a calibrated HP, NP, or LP meal daily. After the meal, on the last day, rats were killed and body composition and blood protein, triglycerides, gut neuropeptides, and hormones were determined. In the brain, neuropeptide mRNAs in the hypothalamus and c-Fos protein and opioid and dopaminergic receptor mRNAs in the nucleus accumbens (NAcc) were measured. Results: Rats fed an LP compared with an NP diet had 7% lower body weight, significantly higher protein intake in a choice experiment (mean ± SD: 30.5% ± 0.05% compared with 20.5% ± 0.05% of energy), higher feed-deprived blood ghrelin, lower postmeal blood leptin, and higher neuropeptide Y (Npy) and corticotropin-releasing hormone (Crh) mRNA expression in the hypothalamus. In contrast to NP, rats fed an LP diet showed postmeal c-Fos protein expression in the NAcc, which was significantly different between meals, with LP < NP < HP. In contrast, in rats adapted to an HP diet compared with an NP diet, energy intake was lower; and in the NAcc, meal-induced c-Fos protein expression was 20% lower, and mRNA expression was 17% higher for dopamine receptor 2 (Drd2) receptors and 38% lower for κ opioid receptor (Oprk1) receptors. Conclusion: A protein-restricted diet induced a reward system-driven appetite for protein, whereas a protein-rich diet reduced the meal-induced activation of reward pathways and lowered energy intake in male rats.

Expected satiation alone does not predict actual intake of desserts.

The degree to which consumers expect foods to satisfy hunger, referred to as expected satiation, has been reported to predict food intake. Yet this relationship has not been established precisely, at a quantitative level. We sought to explore this relationship in detail by determining whether expected satiation predicts the actual intake of semi-solid desserts. Two separate experiments were performed: the first used variations of a given food (eight apple purées), while the second involved a panel of different foods within a given category (eight desserts). Both experiments studied the consumption of two products assigned to volunteers based on their individual liking and expected satiation ratings, given ad libitum at the end of a standardised meal. A linear model was used to find predictors of food intake and included expected satiation scores, palatability scores, BMI, age, sex, TFEQ-R, TFEQ-D, water consumption during the meal, reported frequency of eating desserts, and reported frequency of consuming tested products as explanatory variables. Expected satiation was a significant predictor of actual food intake in both experiments (apple purée: F(1,97) = 18.60, P < .001; desserts: F(1,106) = 9.05, P < .01), along with other parameters such as product palatability and the volunteers' age, sex and food restriction (variation explained by the model/expected satiation in the experiments: 57%/23% and 36%/17%, respectively). However, we found a significant gap between expected and actual consumption of desserts, on group and on individual level. Our results confirm the importance of expected satiation as a predictor of subsequent food intake, but highlight the need to study individual consumption behaviour and preferences in order to fully understand the role of expected satiation.

Fructo-oligosaccharides reduce energy intake but do not affect adiposity in rats fed a low-fat diet but increase energy intake and reduce fat mass in rats fed a high-fat diet.

The ingestion of low or high lipid diets enriched with fructo-oligosaccharide (FOS) affects energy homeostasis. Ingesting protein diets also induces a depression of energy intake and decreases body weight. The goal of this study was to investigate the ability of FOS, combined or not with a high level of protein (P), to affect energy intake and body composition when included in diets containing different levels of lipids (L). We performed two studies of similar design over a period of 5weeks. During the first experiment (exp1), after a 3-week period of adaptation to a normal protein-low fat diet, the rats received one of the following four diets for 5weeks (6 rats per group): (i) normal protein (14% P/E (Energy) low fat (10% L/E) diet, (ii) normal protein, low fat diet supplemented with 10% FOS, (iii) high protein (55%P/E) low fat diet, and (iv) high protein, low fat diet supplemented with 10% FOS. In a second experiment (exp2) after the 3-week period of adaptation to a normal protein-high fat diet, the rats received one of the following 4 diets for 5weeks (6 rats per group): (i) normal protein, high fat diet (35% of fat), (ii) normal protein, high fat diet supplemented with 10% FOS, (iii) high protein high fat diet and (iv) high protein high fat diet supplemented with 10% FOS. In low-fat fed rats, FOS did not affect lean body mass (LBM) and fat mass but the protein level reduced fat mass and tended to reduce adiposity. In high-fat fed rats, FOS did not affect LBM but reduced fat mass and adiposity. No additive or antagonistic effects between FOS and the protein level were observed. FOS reduced energy intake in low-fat fed rats, did not affect energy intake in normal-protein high-fat fed rats but surprisingly, and significantly, increased energy intake in high-protein high-fat fed rats. The results thus showed that FOS added to a high-fat diet reduced body fat and body adiposity.