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The aim of this study was to investigate the effect of 6-weeks resistance training (RT) on appetite, energy intake and body composition in young women with and without obesity, and to examine the relationship between these variables. Thirty-five young women were divided according to the amount of body fat [with obesity (n = 16) and without obesity (n = 19)]. Appetite was assessed through self-reported hunger, fullness, desire to eat, satiety quotient, food frequency diary and motivations to eat palatable food (power of food scale) in both fasted and fed states (after a standardized breakfast). Energy intake and body composition were evaluated at pre- and post-6 weeks of RT. Results showed that self-reported hunger increased significantly in both fasted and fed states (p = 0.007 and p = 0.029, respectively), while self-reported fullness decreased at the fasted state (p = 0.030) in both groups. There were no significant effects for desire to eat fatty, sweet, savory and salty foods, motivation to eat palatable foods, or for total energy intake. Food frequency analysis indicated a decrease in consumption of soup and past (p = 0.045), vegetables and eggs (p = 0.034), and leafy vegetables (p = 0.022) in both groups. Fat-free mass increased significantly in both groups (p = 0.011 and p = 0.003), while fat mass did not show significant changes. There were no correlations between changes in appetite/energy intake and changes in body composition. In conclusion, following the 6-week RT program, both women with and without obesity exhibited increased self-reported hunger alongside decreased fullness, suggesting an increase in orexigenic drive. However, neither group showed an increase in energy intake and fat mass, while both groups experienced an increase in fat-free mass. Registered under Brazilian Registry of Clinical Trials n°. RBR-1024f4qs., Competing Interests: Declarations of interest The authors have no conflicts of interest to disclose., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Few studies have investigated the effect of hydration status on appetite for food in healthy adults. Prior work suggests hydration status does not alter appetite or energy intake, with mixed findings regarding appetite hormone secretion. However, an extensive investigation into both the psychological and physiological appetitive responses to hydration status has never been conducted., Objective: To investigate the effect of hydration status on multiple facets of appetite., Design: After 3 days pre-trial standardization, a range of appetite tasks were conducted when hypohydrated (HYPO) and euhydrated (EUHY) in 16 healthy participants (8 men). Hydration status was manipulated via dehydration in a heat tent for 60 min and subsequent fluid restriction (HYPO) or replacement (EUHY). The next day, a food reward computer task was completed followed by an ad libitum pasta meal. Pre- and post-prandial visual analogue scales assessing hunger, fullness, and flavour desires (sweet, salty, savoury and fatty) were additionally completed. Blood samples were taken the previous day before the hydration interventions in a euhydrated state, and in the fasted and post-prandial state during HYPO and EUHY., Results: HYPO induced -1.9 ± 1.2% body mass change, compared to -0.2 ± 0.6% , with accompanying changes in markers of hypohydration which were not seen during EUHY. A higher desire for foods was associated with a higher water content but the association was weaker in EUHY compared to HYPO, (β= -0.33 mm/g of food water content, p < 0.001) in the food reward task. Visual analogue scales showed similar hunger and fullness between interventions, but during HYPO there was consistently higher thirst (average range in difference 27-32 mm across all time points) and lower fasted desire for salt (-23, 95% CI -10, -35 mm). Ad libitum energy intake (HYPO 1953 ± 742 kJ, EUHY 2027 ± 926 kJ; p = 0.542) and post-prandial ghrelin concentrations (HYPO 180 ± 65 pg mL -1 , EUHY 188 ± 71 pg mL -1 ; p = 0.736) were similar by hydration status., Conclusions: An acute manipulation to hydration status altered desire for salt and foods of differing water contents, but did not influence energy intake at an ad libitum pasta meal. Further research should investigate whether these appetites would alter food choice., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Previous studies have revealed that increasing people's blood glucose level via drinking a soft drink containing sugar makes their financial decisions more future-oriented. This study extends these previous findings, testing whether the effect holds when blood glucose level is increased via intake of a normal meal (i.e., breakfast) rather than a sweet drink. Moreover, we test whether the size of the meal consumed (i.e., a normal vs. an oversized meal) can have a quantitatively different impact on levels of delay discounting. In two experiments using different time intervals between food consumption and discounting tasks (i.e., 60 min and 10 min), we successfully increased both blood glucose level and satiation level. Despite this, our results revealed that neither consumption of the meal itself nor the size of the meal influenced a preference for future rewards over present rewards. This suggests that satisfying hunger and increasing blood glucose level are not sufficient to make people more future-oriented., (Copyright © 2019 Elsevier Inc. All rights reserved.)

To determine whether breastfeeding alters women's interest in eating foods of different taste categories, we surveyed women at their 6-week post-partum check-up, asking them to rate their interest in eating various foods. Regardless of whether women responded in English or Spanish, they indicated greatest interest in eating sweet-tasting foods and least interest in eating sour-tasting foods, independent of whether they were breastfeeding. In general, the interest in eating foods of all taste qualities foods was increased in women who were breastfeeding; however, interest in eating salty and sour foods was not altered by breastfeeding in Spanish respondants. It is noteworthy that interest in eating foods of specific taste categories correlated with ratings of hunger in women who were not breastfeeding, but not in women who were breastfeeding. Thus, although breastfeeding women had a greater interest in eating foods of all taste categories, their interest does not appear to be driven solely by hunger. Finally, independent of breastfeeding, the interest in eating specific foods within taste categories differed between English and Spanish respondants, with Spanish respondants reporting greater interest in eating both nuts and bananas compared to English respondants. Together, these findings represent an initial approach to assess the impact of breastfeeding on interest in eating different types of food, and of how reproductive status and cultural differences may interact to affect food preferences and thereby to alter food choices., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background & Aims: Women with polycystic ovary syndrome (PCOS) have greater predisposition to obesity, but the mechanisms are still unknown. Hyperinsulinemia, insulin resistance and low levels of ghrelin are common in this group. For the purposes of the present study, it was assumed that such changes could have an influence on hunger. This study aimed to assess the hunger pattern before and after an ad libitum meal and the association between insulin and plasma ghrelin with hunger perception in women with obesity, with and without PCOS., Method: This cross-sectional study included 53 women with obesity, 30 with PCOS, and 23 controls (with obesity but without PCOS). Insulin, ghrelin, glucose and subjective ratings of hunger (by 100 mm visual analogue scales) were analyzed in a fasting state, preprandially at 12:00 before the ad libitum meal, and postprandially 15, 45, 75 and 135 min after the beginning of the ad libitum meal., Results: There was a significant increase in hunger one hour after the beginning of the ad libitum meal (75 min) in the PCOS group (p = .01) compared to 15 min, whereas this only occurred after 135 min in the control group (2 h later). The usual energy intake adjusted by the intra-individual variability was higher in the PCOS group than in the control group (2309 ± 461 kcal·d -1  × 2124 ± 480 kcal·d -1 ; p = .04). The concentrations of insulin and ghrelin, in both preprandial and postprandial periods, were not associated with the perception of hunger., Conclusions: Women with obesity and PCOS had an earlier return of hunger in the postprandial period after an ad libitum meal, but there was not associated with postprandial ghrelin and insulin levels., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: The prevalence of obesity has led the scientific community to investigate the cause of this multifactorial metabolic disorder. Highly palatable foods can stimulate hedonic hunger and could be a cause of obesity. In the present study, for the first time, the relationships between insulin, leptin and BDNF levels and hedonic hunger were investigated. Ninety overweight and obese women were studied. The demographic characteristics and anthropometric indices were measured and the power of food scale (PFS) questionnaire was used to assess hedonic hunger. In addition, the serum levels of fasting blood sugar (FBS), insulin, leptin and brain-derived neurotrophic factor (BDNF) were determined. Regression analysis was used to predict hedonic hunger using age, body mass index (BMI) and body fat percentage (BFP) as covariates. The levels of insulin and leptin were found to be significantly correlated with the PFS total score and the scores of PFS-FA (food available), PFS-FP (food present), and PFS-FT (food taste). The BDNF level showed a significant negative correlation only with PFS-FT. Multiple regression analysis showed statistically significant associations between hedonic hunger and levels of insulin [β coefficient: 1.29 (SE: 0.32), p < .001], leptin [β coefficient: 0.2 (SE: 0.09), p = .023] and BDNF [β coefficient: -6.29 (SE: 2.81), p = .028]. These three values were found to be predictors of hedonic hunger. The findings provide further evidence in favor of the role of these hormones in hedonic hunger., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background: Exercise-induced weight loss is often less than expected and highly variable in men and women. Behavioural compensation for the exercise-induced energy deficit could be through energy intake (EI), non-exercise physical activity (NEPA) or sedentary behaviour (SB). We investigated this issue in women., Methods: Twenty-four overweight [body mass index (BMI) M = 27.9 kg/m 2 , SD = 2.7] women [age M = 33.1 years, SD = 11.7] completed 12-weeks of supervised exercise (5×500kcal per week) in a non-randomised, pre-post intervention study. Body mass (BM), waist circumference (WC), body composition, resting metabolic rate (RMR), total daily EI, individual meals, appetite sensations and appetite-related peptides were measured at baseline (week 0) and post-intervention (week 12). Free-living physical activity (PA) and SB were measured (SenseWear) at baseline, week 1 and 10 of the exercise intervention, and at post-intervention (week 13)., Results: Following the 12-week exercise intervention BM [p = .04], BMI [p = .035], WC [p < .001] and fat mass (FM) [p = .003] were significantly reduced, and fat-free mass (FFM) significantly increased [p = .003]. Total [p = .028], ad libitum [p = .03] and snack box EI [p = .048] were significantly increased and this was accompanied by an increase in hunger [p = .01] and a decrease in fullness [p = .03] before meals. The peptides did not explain changes in appetite [p > .05]. There was no compensatory reduction in NEPA [p > .05] and no increase in SB, rather there was a decrease in SB during the exercise intervention [p = .03]., Conclusions: Twelve-weeks of supervised aerobic exercise resulted in a significant reduction in FM and an increase in FFM. Exercise increased hunger and EI which only partially compensated for the increase in energy expenditure. There was no evidence for a compensatory reduction in NEPA or an increase in SB. Dietary intervention, as an adjunct to exercise, may offset the compensatory increase in EI and result in a greater reduction in BM., Trial Registration: Our trial was retrospectively registered on the International Standard Randomised Controlled Trials Registry (ISRCTN78021668, 27th September 2016) and can be found here: https://doi.org/10.1186/ISRCTN78021668., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Many diets employ regular periods of fasting that extend beyond a typical overnight fast (i.e. intermittent fasting [IF]). Evaluation of acute fasting responses provides information concerning the potential theoretical rationale for IF. The purpose of the present investigation was to assess the test-retest reliability of hunger-related variables during 24-hour fasts and the relationship between these variables and body composition, as well as subsequent energy intake (EI) after fasting. Eleven participants (6 F, 5 M) completed two 24-hour fasts after being provided a 3-day standardized weight-maintenance diet. From 16 to 24 h of fasting, participants were directly observed and provided hourly assessments of hunger, desire to eat (DTE), prospective food consumption (PFC), fullness and energy. After the fast, participants were allowed ad libitum food consumption, and compensation was calculated as EI relative to weight-maintenance energy needs. Test-retest reliability for hunger-related assessments at particular durations of fasting was evaluated using intraclass correlation coefficients (ICC), changes in dependent variables were evaluated using ANOVA with repeated measures, and relationships between variables were explored using bivariate correlations. At 16 h of fasting, the ICCs for all hunger-related assessments were statistically significant (r = 0.67-0.91; p ≤ 0.05). However, as the fast progressed, reliability varied substantially. When averaged across the nine measurements, the ICCs were: 0.81 (fullness), 0.74 (PFC), 0.67 (energy), 0.44 (DTE) and 0.36 (hunger). Body fat percentage was significantly correlated with changes in PFC (r = 0.62, p = 0.04), hunger (r = 0.66, p = 0.03), DTE (r = 0.71, p = 0.02), and fullness (r = -0.63, p = 0.04), but not energy (r = -0.16, p = 0.64). Average EI compensation was only 60% of weight-maintenance needs, but substantial variability was observed (7 to 110% compensation). Compensation was significantly correlated with changes in PFC (r = 0.72, p = 0.01), hunger (r = 0.63, p = 0.04) and DTE (r = 0.60, p = 0.05), but not fullness (r = 0.58, p = 0.06) or energy (r = 0.35, p = 0.29). Compensation and body fat percentage were not correlated (r = 0.03, p = 0.94). The percent of energy intake from fat and protein increased after the fast (29.9 to 37.3% and 13.8 to 16.8%; p < 0.05), while the percent of energy intake from carbohydrate decreased (56.4 to 46.0%; p = 0.02). These results may have implications for IF programs. It is possible that the implementation of multiple "test fasts," in which subjective variables and subsequent energy intake are evaluated, could be used to identify candidates who may be more likely to benefit from an IF program., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Clinical and preclinical findings suggest that individuals with abnormal responses to reward cues (stimuli associated with reward) may be at risk for maladaptive behaviors including obesity, addiction and depression. Our objective was to develop a new paradigm for producing appetitive conditioning using primary (food) rewards in humans, and investigate the equivalency of several outcomes previously used to measure appetitive responses to conditioned cues. We used an individualized food reward, and multimodal subjective, psychophysiological and behavioral measures of appetitive responses to a conditioned stimulus (CS) that predicted delivery of that food. We tested convergence among these measures of appetitive response, and relationships between these measures and action impulsivity, a putative correlate of appetitive conditioning. 90 healthy young adults participated. Although the paradigm produced robust appetitive conditioning in some measures, particularly psychophysiological ones, there were not strong correlations among measures of appetitive responses to the CS, as would be expected if they indexed a single underlying process. In addition, there was only one measure that related to impulsivity. These results provide important information for translational researchers interested in appetitive conditioning, suggesting that various measures of appetitive conditioning cannot be treated interchangeably., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Incentive salience theory (IST) suggests that 'wanting' and liking are dissociable processes. We argue that explicit measures of wanting in humans can reflect the impact of implicit 'wanting' as envisaged by IST, suggesting that dissociations should also be evident for explicit judgments of wanting and liking. To test this, participants were asked to make ratings of these variables for 8 palatable snack foods - and in a related test salivation rate was also assessed. Participants viewed and sniffed each snack food and rated wanting, and then sampled it and rated liking and whether they wanted more of it. Following a lunch eaten to satiety, and composed in part of half of the palatable snack foods, participants repeated their evaluations of the snack foods (and salivation rate). Liking changed less across lunch than wanting and want more ratings, the last-mentioned changing the most. Change in liking was associated with change in salivation rate, independent of wanting, and change in wanting was associated with change in hunger independent of liking. We argue these dissociations are consistent with 'wanting' influencing explicit wanting, and that want more ratings may represent a 'purer' measure of IST 'wanting'., (Copyright © 2017 Elsevier Inc. All rights reserved.)

A history of dieting to lose weight has been shown to be a robust predictor of future weight gain. A potential factor in propensity towards weight gain is the nature of people's reactions to the abundance of highly palatable food cues in the environment. Event Related Potentials (ERPs) have revealed differences in how the brain processes food cues between obese and normal weight individuals, as well as between restrained and unrestrained eaters. However, comparisons by weight status are not informative regarding whether differences predate or follow weight gain in obese individuals and restrained eating has not consistently been found to predict future weight gain. The present study compared ERP responses to food cues in non-obese historic dieters (HDs) to non-obese never dieters (NDs). HDs showed a blunted N1 component relative to NDs overall, and delayed N1 and P2 components compared to NDs in the hungry state, suggesting that early, perceptual processing of food cues differs between these groups, especially when food-deprived. HDs also showed a more hunger-dependent sustained ERP (LPP) compared to NDs. Future research should test ERP-based food cue responsivity as a mediator between dieting history and future weight gain to better identify those most at risk for weight gain as well as the nature of their vulnerability., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: The process of gastric emptying determines how fast gastric content is delivered to the small intestine. It has been shown that solids empty slower than liquids and that a blended soup empties slower than the same soup as broth and chunks, due to the liquid fraction emptying more quickly. This process of 'gastric sieving' has not been investigated for liquid foods., Objective: To determine whether gastric sieving of water can also occur for liquid foods., Method: Two groups of men participated in a parallel design (n=15, age 22.6±2.4y, BMI 22.6±1.8kg/m 2 , and n=19, age 22.2±2.5y, BMI 21.8±1.5kg/m 2 ) and consumed an isocaloric shake (2093kJ, CARBOHYDRATES: 71g, FAT: 18g, PROTEIN: 34g), either in a 500-mL version (MIXED) or as a 150-mL shake followed by 350mL water (SEPARATE). Participants provided appetite ratings and were scanned using MRI to determine gastric emptying rate and volume at three time-points within 35min post ingestion., Results: Gastric emptying the percentage emptied in 35min was significantly smaller for MIXED (29±19%) than for SEPARATE (57±11%, p<0.001)., Conclusion: In the present study we show that gastric sieving can occur for liquid foods; water is able to drain from the stomach while a layer of nutrient rich liquid is retained. In indirect gastric emptying measurements, the behavior of labelling agents may be affected by the layering and confound emptying measurements., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Asymmetrical alpha activation in the prefrontal cortex (frontal asymmetry) in electroencephalography (EEG) has been related to eating behavior. Prior studies linked dietary restraint with right frontal asymmetry [1] and disinhibition with left frontal asymmetry [2]. The current study simultaneously assessed restrained eating and hedonic hunger (drive for food reward in the absence of hunger) in relation to frontal asymmetry. Resting-state EEG and measures of restrained eating (Revised Restraint Scale; RRS) and hedonic hunger (Power of Food Scale; PFS) were assessed in 61 non-obese adults. Individually, hedonic hunger predicted left asymmetry. However, PFS and RRS were correlated (r=0.48, p<0.05) and there was a significant interaction between PFS and RRS on frontal asymmetry, p<0.01. Results indicated that those high in hedonic hunger exhibited left asymmetry irrespective of RRS scores; among those low in PFS, only those high in RRS showed right asymmetry. Results were consistent with literature linking avoidant behaviors (restraint) with right-frontal asymmetry and approach behaviors (binge eating) with left-frontal asymmetry. It appears that a strong drive toward palatable foods predominates at a neural level even when restraint is high. Findings suggest that lateralized frontal activity is an indicator of motivation both to consume and to avoid consuming highly palatable foods., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The post-prandial satiety response and "second-meal effect" of a viscous fibre supplement PolyGlycopleX(®) (PGX(®)) was evaluated in a single-blind, randomised controlled crossover study of 14 healthy adult women. The two hour post-prandial satiety response, expressed as the area under the curve (AUC) of perceived hunger/fullness score versus post-prandial time, of a standardised evening meal with concurrent intake of either PGX softgel or rice flour softgel (control) was determined. On the following morning, after an overnight fast, the four hour satiety response to a standardised breakfast with no softgel supplementation was assessed. A significantly higher satiety response (AUC) to the standard dinner for the PGX-supplemented dinner compared with the control dinner (p=0.001) was found. No significant difference (p=0.09) was observed in the satiety response (AUC) of the breakfast regardless of which supplemented-dinner had been consumed prior, however the p value indicated a trend towards a higher response to the breakfast following the PGX-supplemented dinner. The fullness scores of the breakfast following the PGX-supplemented dinner at 15, 30, 90, 120, 150, 180, 210 and 240min post-prandial were significantly higher than those for the breakfast following the control dinner (p=<0.001, 0.007, 0.009, 0.009, 0.049, 0.03, 0.003 and <0.001 respectively). PGX supplementation at dinner increased the satiety effects of both the dinner itself and the subsequent un-supplemented breakfast; a "second meal effect" indicting the potential for this fibre supplement to induce extended satiety., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objectives: To seek insights into the relationship between chewing, appetite, food intake and gut hormones, and to consider potentially useful recommendations to promote benefits of chewing for weight management., Materials and Methods: Papers were obtained from two electronic databases (Medline and Cochrane), from searches of reference lists, and from raw data collected from the figures in the articles. A total of 15 papers were identified that detailed 17 trials. All 15 papers were included in the systematic review; however, a further five studies were excluded from the meta-analysis because appropriate information on hunger ratings was not available. The meta-analysis was conducted on a total of 10 papers that detailed 13 trials., Results: Five of 16 experiments found a significant effect of chewing on satiation or satiety using self-report measures (visual analogue scales, VASs). Ten of 16 experiments found that chewing reduced food intake. Three of five studies showed that increasing the number of chews per bite increased relevant gut hormones and two linked this to subjective satiety. The meta-analysis found evidence of both publication bias and between study heterogeneity (IA(2) = 93.4%, tau(2) = 6.52, p < 0.001) which decreased, but remained, when covariates were considered. Analysis of the heterogeneity found a substantial effect of the fasting period where the duration of fasting influenced the decrease in hunger due to chewing. Prolonged mastication significantly reduces self-reported hunger levels (hunger: − 2.31 VAS point, 95% CI [− 4.67, − 1.38], p < 0.001)., Conclusions: Evidence currently suggests that chewing may decrease self-reported hunger and food intake, possibly through alterations in gut hormone responses related to satiety. Although preliminary, the results identify a need for additional research in the area. Focused, uniform, experimental designs are required to clearly understand the relationships that exist between mastication, appetite, satiety, food intake and, ultimately, body weight.

This study investigated cardiovascular functioning, mood, and eating-related psychological factors at rest and in response to mental stress in three groups of women: 1) Obese women with binge eating disorder (BED; n=9); 2) obese non-BED women (n=15); and 3) normal weight (NW) non-BED women (n=15). Compared to both obese and NW non-BED women, obese women with BED showed heightened overall blood pressure and reported greater depression symptoms, perceived stress, and eating-related psychopathology. Additionally, obese women with BED reported greater overall negative affect and state anxiety compared to obese non-BED women. The heart rate response to stress was blunted in the obese BED group compared to the other groups, but this effect was no longer significant after controlling for baseline differences in depression. Correlational analyses revealed a positive association between stress-induced changes in hunger and cardiovascular measures only in obese women with BED. Longitudinal studies are needed to determine if stress dysregulation and stress-induced increases in hunger contribute to the onset and/or maintenance of BED. In particular, studies utilizing an additional NW BED control group are warranted in order to further examine the impact of BED above and beyond the impact of obesity on psychophysiological functioning and to inform the growing literature regarding stress-related factors that distinguish the BED and obesity phenotypes., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The core defining features of bulimia nervosa (BN) are repeated binge eating episodes and inappropriate compensatory (e.g., purging) behavior. Previous studies suggest an abnormal post-prandial response in the satiety-signaling peptide cholecystokinin (CCK) in persons with BN. It is unknown whether this altered response persists following remission or if it may be a potential target for the development of clinical treatment strategies. To examine the nature of this altered response, this study assessed whether CCK normalizes following remission from BN (RBN). This study prospectively evaluated the plasma CCK response and corresponding eating behavior-related ratings (e.g., satiety, fullness, hunger, urge to binge and vomit) in individuals with BN-purging subtype (n=10), RBN-purging subtype (n=14), and healthy controls (CON, n=13) at baseline, +15, +30, and +60 min following the ingestion of a standardized liquid test meal. Subject groups did not significantly differ in CCK response to the test meal. A significant relationship between CCK response and satiety ratings was observed in the RBN group (r=.59, p<.05 two-tailed). A new and unanticipated finding in the BN group was a significant relationship between CCK response and ratings of "urge to vomit" (r=.86, p<.01, two-tailed). Unlike previous investigations, CCK response did not differ in BN and CON groups. Thus the role of symptom severity remains an area of further investigation. Additionally, findings suggest that in this sample, CCK functioning following remission from BN-purging subtype is not different from controls. It remains unknown whether or not CCK functioning may be a protective or liability factor in the stabilization and recovery process. Replication studies utilizing a larger sample size are needed to further elucidate the role of CCK in recovery from BN and its potential target of related novel treatment strategies., (© 2013 Elsevier Inc. All rights reserved.)

Unlabelled: A unifying physiological explanation of the urge to initiate eating is still not available as human hunger in meal-to-meal eating may not be under homeostatic control. We hypothesized that a central circadian and a gastrointestinal ultradian timing mechanism coordinate non-deprivation meal-to-meal eating. We examined hunger as a function of time of day, inter-meal (IM) energy expenditure (EE), and concentrations of proposed hunger-controlling hormones ghrelin, leptin, and insulin., Methods: In two crossover studies, 10 postmenopausal women, BMI 23-26 kg/m(2) engaged in exercise (EX) and sedentary (SED) trials. Weight maintenance meals were provided at 6h intervals with an ad libitum meal at 13 h in study 1 and 21 h snack in study 2. EE during IM intervals was measured by indirect calorimetry and included EX EE of 801 kcal in study 1, and 766-1,051 kcal in study 2. Hunger was assessed with a visual analog scale and blood was collected for hormonal determination., Results: Hunger displayed a circadian variation with acrophase at 13 and 19 h and was unrelated to preceding EE. Hunger was suppressed by EX between 10 and 16 h and bore no relationship to either EE during preceding IM intervals or changes in leptin, insulin, and ghrelin; however leptin reflected IM energy changes and ghrelin and insulin, prandial events., Conclusions: During non-deprivation meal-to-meal eating, hunger appears to be under non-homeostatic central circadian control as it is unrelated to EE preceding meals or concentrations of proposed appetite-controlling hormones. Gastrointestinal meal processing appears to intermittently suppress this control and entrain an ultradian hunger pattern., (© 2013 Elsevier Inc. All rights reserved.)

Rats learn to prefer flavors associated with postingestive effects of nutrients. The physiological signals underlying this postingestive reward are unknown. We have previously shown that rats readily learn to prefer a flavor that was consumed early in a multi-flavored meal when glucose is infused intragastrically (IG), suggesting rapid postingestive reward onset. The present experiments investigate the timing of postingestive fat reward, by providing distinctive flavors in the first and second halves of meals accompanied by IG fat infusion. Learning stronger preference for the earlier or later flavor would indicate when the rewarding postingestive effects are sensed. Rats consumed sweetened, calorically-dilute flavored solutions accompanied by IG high-fat infusion (+ sessions) or water (- sessions). Each session included an "Early" flavor for 8min followed by a "Late" flavor for 8min. Learned preferences were then assessed in two-bottle tests (no IG infusion) between Early(+) vs. Early(-), Late(+) vs. Late(-), Early(+) vs. Late(+), and Early(-) vs. Late(-). Rats only preferred Late(+), not Early(+), relative to their respective (-) flavors. In a second experiment rats trained with a higher fat concentration learned to prefer Early(+) but more strongly preferred Late(+). Learned preferences were evident when rats were tested deprived or recently satiated. Unlike with glucose, ingested fat appears to produce a slower-onset rewarding signal, detected later in a meal or after its termination, becoming more strongly associated with flavors towards the end of the meal. This potentially contributes to enhanced liking for dessert foods, which persists even when satiated., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Despite living in an obesogenic environment, some individuals maintain a thin phenotype compared to the majority who are at risk for weight gain and obesity. Understanding how these different phenotypes regulate energy intake is critical. The objective of this study was to examine the differences in neuronal response to visual food cues in adults recruited as either obesity-resistant (OR) or obesity-prone (OP) based on self-identification, BMI, and personal/family weight history. 25 OR and 28 OP individuals were studied after 4 days of eucaloric energy intake. Functional magnetic resonance imaging (fMRI) was performed in the fasted and acute fed states (30 min after a test meal) while subjects viewed images of foods of high hedonic value and neutral non-food objects. Measures of appetite using visual analog scales were performed before and every 30 min after the test meal for 3 h. In the fasted state, food as compared to nonfood images elicited significant response in the insula, somatosensory cortex, parietal cortex, and visual cortex in both OR and OP. The acute fed state resulted in significant attenuation of these and other brain areas in the OR but not OP individuals. Furthermore, OP as compared to OR individuals showed greater activation of medial and anterior prefrontal cortex (PFC) in response to the test meal. Adjusting for fat mass did not impact these results. Attenuation of insula/PFC response to food images in the fed state was associated with greater reductions in hunger. These findings suggest that individuals prone to weight gain and obesity have altered neuronal responses to food cues in brain regions known to be important in energy intake regulation. These altered responses may represent an important mechanism contributing to excess energy intake and risk for obesity., (Copyright © 2013 Elsevier Inc. All rights reserved.)

It has been suggested that obese individuals over-eat in order to compensate for deficits in the dopaminergic reward system. The current study used acute tyrosine/phenylalanine depletion (ATPD) to investigate the effect of reduced dopamine function on appetite and the reward value of food in healthy volunteers. The compensatory-eating hypothesis would predict an increase in the reward value and consumption of food following depletion by this method. In a double-blind, counterbalanced, crossover study, 17 male participants (mean age=29.2 (SEM=2.7) years; mean body mass index=24.4 (SEM=0.6) kg/m(2)) were administered with a tyrosine/phenylalanine-free mixture (TYR/PHE-free; depletion condition) and a balanced amino acid mixture (BAL; control). Plasma amino acid levels were measured at baseline and peak depletion (300 min). Appetite, willingness to pay for food, liking, desired portion size and ad libitum food intake were also assessed. The TYR/PHE-free mixture was associated with significant decreases in tyrosine, phenylalanine, and the ratio of tyrosine+phenylalanine to the other large neutral amino acids (all p<.001). There were no effects on our measures of willingness to pay for food or liking. However, in the TYR/PHE-free condition, participants reported significantly lower levels of hunger following a fixed-test meal relative to the BAL condition. In conclusion, we found no evidence for compensatory eating following ATPD. Our results also provide support for the role of dopamine in motivational components of eating., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Obesity is a major health problem that can be influenced by eating behaviors. Evidence suggests that the sensory properties of food influence eating behaviors and lead to overeating and overweight. A previous genome-wide linkage scan for eating behavior traits assessed with the Three-Factor Eating Questionnaire (cognitive dietary restraint, disinhibition and hunger) performed in the Quebec Family Study (QFS) revealed a quantitative trait locus for disinhibition on chromosome 19p13. This region encodes a cluster of seven olfactory receptor (OR) genes, including OR7D4, previously associated with odor perceptions. Direct sequencing of the OR7D4 gene revealed 16 sequence variants. Nine OR7D4 sequence variants with minor allele frequency (MAF)>1% as well as 100 SNPs spanning the cluster of OR genes on 19p13 were tested for association with age- and sex-adjusted eating behaviors as well as adiposity traits in 890 subjects. One OR7D4 sequence variant (rs2878329 G>A) showed evidence of association with reduced levels of adiposity (p=0.03), cognitive dietary restraint (p=0.05) and susceptibility to hunger (p=0.008). None of the OR7D4 SNPs was associated with disinhibition, but a SNP (rs2240927) in another OR gene (OR7E24) showed evidence of association (p=0.03). Another SNP in the OR7G3 gene (rs10414255) was also found to be associated with adiposity and eating behaviors. These results are the first to suggest that variations in human olfactory receptor genes can influence eating behaviors and adiposity. The associations reported in the present study should be interpreted with caution considering the number of tests performed and considered as potential new hypotheses about the effects OR polymorphisms on eating behaviors and obesity that need to be further explored in other populations., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Whole grain rye products have previously been shown to increase feelings of satiety for up to 8h after intake under standardized conditions. This study was set out to investigate the sustainability of the satiating effect after regular consumption of breakfast meals with whole grain rye porridge or refined wheat bread. The study was randomized, cross-over and double-blind. Healthy subjects (n=24) were randomly assigned to daily consumption of iso-caloric standardized breakfast meals with whole grain rye porridge or refined wheat bread for two 3-wk phases, separated by a wash out of 3-4weeks. Each intervention phase had 3 scheduled visit days (days 1, 8 and 22) when appetite ratings (hunger, satiety and desire to eat) were registered for 24h at standardized conditions. Orocecal transit time (salicylazosulfapyridine/sulfapyridine method) and breath hydrogen as an indicator of colonic fermentation were measured at day 8 of each 3-wk phase in a subgroup (n=16). To investigate effects of breakfast on free-living food intake, 3-day weighed food diaries were self-registered during both intervention phases. Whole grain rye porridge breakfast resulted in higher ratings of satiety and lower hunger and desire to eat during 4h post consumption compared to refined wheat bread breakfast (p<0.001). This effect was sustained throughout the 3-wk study phases. Unlike previous studies, the effects did not persist into the afternoon (4-8h). The orocecal transit times after consumption of both breakfasts were similar and in the range of 5-6h. The rye porridge resulted in high levels of breath hydrogen 4-8h after intake, showing extensive colonic fermentation. This was however not related to any changes in appetite during this time-period. There were no significant differences in self-reported macronutrient- and energy intake between diets. This study shows that the satiating effect of rye persists after repeated daily consumption for up to three weeks. Clinicaltrials.gov Identifier: NCT01117363., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Weight gain and appetite regulation are complex interplays between internal and external cues. Our aim was to investigate the association of eating behaviors with ghrelin taking into account lifestyle. We conducted a cross-sectional analysis in a sample of first-year university students at the Université de Sherbrooke. We collected medical history, anthropometric measurements, vital signs, fitness index, and fasting blood samples. Questionnaires included a lifestyle questionnaire and the Three-Factor Eating Questionnaire (TFEQ) estimating dietary restraint, disinhibition and hunger. We recruited 308 participants aged 20.7±3.2 years and a mean BMI of 23.3±3.4 kg/m(2). Hunger score was significantly associated with ghrelin levels (r=0.11, P<0.05). In women, this association was independent of age, BMI, dietary and lifestyle factors (P=0.02). The association between ghrelin level and hunger score was observable in leaner individuals (r=0.28, p<0.0001) but not in heavier individuals (r=-0.08, p=0.34; stratified by BMI < vs > 22.6 kg/m(2)). Restraint (R) and disinhibition (D) were not associated with ghrelin levels. The three eating behaviors demonstrated expected correlations with lifestyle supporting the validity of the TFEQ in this cohort. In conclusion, we demonstrated that ghrelin, a biological marker, is associated with self-reported perception of hunger, independently of anthropometric measures and lifestyle., (Copyright © 2011 Elsevier Inc. All rights reserved.)

The anticipation of food intake comprises endocrine changes that according to animal experiments include a rise in HPA axis activity. In humans, HPA axis responses to food anticipation and withdrawal, although of clinical relevance, have not been thoroughly examined. We assessed neuroendocrine and psychological effects of food anticipation and of withholding anticipated food in healthy human subjects. Food anticipation was induced in 14 men at 0800 h by the announcement and subsequent presentation of a breakfast buffet. The expected meal was surprisingly withheld at 1000 h under the pretense of an organizational problem. Fifteen fasted controls were informed at 0800 h that they would remain fasted throughout the experiments. In both groups, hunger, mood and circulating concentrations of glucose, insulin, cortisol, ACTH, leptin and ghrelin were assessed. At 1200 h, all subjects were allowed to eat from a plate of cookies. Compared to non-anticipation, food anticipation was associated with a relative increase in serum cortisol levels, an acute drop in plasma glucose and increased self-rated hunger. When anticipated food was withheld, self-rated mood deteriorated and cortisol levels remained elevated, while plasma glucose levels decreased with a delay of 50 min. Other endocrine parameters and cookie intake were comparable between groups. Our results indicate that food anticipation without subsequent food reward increases cortisol levels and reduces blood glucose availability. They support the assumption that dietary restraint, being associated with habitually extended periods of anticipating food that is temporarily withheld, may contribute to the development of overweight by detrimental effects on HPA-axis activity., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Stress may induce eating in the absence of hunger, possibly involving changes in food reward, i.e. 'liking' and 'wanting'. The objective of this study was to assess the effects of acute psychological stress on food reward, and on energy intake, in visceral overweight (VO) vs. normal weight (NW) subjects. Subjects (27 NW, age=26 ± 9 yrs, BMI=22 ± 2 kg/m²; 15 VO, age=36 ± 12 yrs, BMI=28 ± 1 kg/m²) came to the university twice, fasted, for either a rest or stress condition (randomized cross-over design). Per test-session 'liking' and 'wanting' for 72 items divided in six categories (bread, filling, drinks, dessert, snacks, and stationery (control)) were measured twice, each time followed by a wanted meal. Appetite profile (visual analogue scales, VAS), heart rate, mood state and level of anxiety (POMS/STAI questionnaires) were measured. High hunger and low satiety (64 ± 19, 22 ± 20 mmVAS) confirmed the fasted state. Elevated heart rate, anger and confusion scores (p ≤ 0.03) confirmed the stress vs. rest condition. Consumption of the first meal decreased hunger, increased satiety, and decreased ranking of 'liking' of bread vs. increased ranking of 'liking' of the control (p<0.001). 'Wanting' for dessert and snacks, energy intake, carbohydrate and fat intake for the second meal stress vs. rest relatively increased in VO vs. decreased in NW (p<0.02). During stress vs. rest VO showed a 6 ± 9% increase in percentage of daily energy requirements consumed over the two meals (p=0.01). To conclude, visceral overweight subjects showed stress-induced food intake in the absence of hunger, resulting in an increased energy intake., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Rats learn to prefer flavors that are followed by postingestive effects of nutrients. This experiment investigated whether the timing of a flavor (specifically, in the first or second half of the meal) influences learning about that flavor. Stronger learning about earlier or later flavors would indicate when the rewarding postingestive effects of nutrients are sensed. Rats with intragastric (IG) catheters drank saccharin-sweetened, calorically-dilute solutions with distinct flavors added, accompanied by IG infusion of glucose (+sessions) or water (-sessions). In both types of sessions, an "Early" flavor was provided for the first 8 min and a "Late" flavor for the last 8 min. Thus, rats were trained with Early(+) and Late(+) in high-calorie meals, and Early(-) and Late(-) in low-calorie meals. Strength of the learned preference for Early(+) and Late(+) was then assessed in a series of two-bottle choice tests between Early(+) vs. Early(-), Late(+) vs. Late(-), Early(+) vs. Late(+), and Early(-) vs. Late(-). Rats preferred both Early(+) and Late(+) over the respective (-) flavors. But Early(+) was only preferred when rats were tested hungry. Late(+) was preferred when rats were tested hungry or recently satiated. This indicates qualitatively different associations learned about flavors at different points in the meal. While not supporting the idea that postingestive effects become most strongly associated with later-occurring ("dessert") flavors, it does suggest a reason dessert flavors may remain attractive in the absence of hunger., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Associative conditioning of satiety indicates that concentrated maltodextrin (cMD) may induce a mildly aversive visceral signal within 20 min of its ingestion, as well as satiating normally. Individuals' awareness of this adverse state was tested on ratings of statistically distinct descriptions of factors liable to suppress hunger, whether distressing or comfortably satisfying. Wanted amount of a food and the pleasantness of eating it correlated highly for each of five foods, once again refuting the widespread presumption that "pleasant" refers to sensory pleasure; hence, as in previous reports, suppression of hunger was measured as a reduction of the averaged pleasantness of functionally related foods. At 20 min after the start of ingestion of a small meal on a near-empty stomach, cMD reliably reduced hunger. The greatest influence on hunger, besides normal sating, was thirst, but there were also tendencies to nausea and bloat, although all less than after a full sized meal. Visceral processes shortly after a meal can create dissociable conscious states, only one of which is satiety for food., (2010 Elsevier Inc. All rights reserved.)

Associations between hunger and eating and between thirst and drinking are generally weak. This stems, in part, from limitations in the measurement of these sensations which generally rely on temporal, motivational, metabolic and/or self-reported descriptive indices. Each is critically reviewed. Also problematic is the fact that the deterministic depletion-repletion concept of ingestive behavior fails to account for influences of a multitude of contravening cognitive, social, sensory and logistical factors. Although hunger and thirst serve some parallel purposes, sharp distinctions are also present with health implications. Of particular note are the observations that thirst ratings are higher and more stable over the day compared to hunger and thirst may be more motivating to drink than hunger is to eat. Coupling these observations with evidence that beverages have limited satiety value, they pose particular challenges and opportunities. Beverages can facilitate the delivery of nutrients to those desiring or requiring them, but also to those where they are not desired or required. The benefits and risks are a function of their use rather than their inherent properties., (Copyright 2010 Elsevier Inc. All rights reserved.)

Sleep restriction alters hormone patterns and appetite in men, but less is known about effects on women. We assessed effects of overnight sleep restriction on cortisol and leptin levels and on appetite in young women. Participants' baseline sleep duration and eating habits were monitored for a week before the study. Salivary cortisol and leptin were sampled from fifteen healthy women (aged 18-25) during two consecutive days: first after a 10h overnight sleep opportunity (Baseline day) and then after a night including only 3h sleep (Post sleep-restriction day). Participants also completed appetite questionnaires on both days. Sleep restriction significantly reduced morning cortisol levels (p=0.02), elevated morning leptin levels (p=0.04), elevated afternoon/evening cortisol area under the curve values (p=0.008), and slowed the decline in cortisol concentration during the day (p=0.04). Hunger and craving scores did not differ significantly between days. A single night of restricted sleep affected cortisol rhythms and morning leptin levels in young women., ((c) 2010 Elsevier Inc. All rights reserved.)

Objective: To investigate the relation between ghrelin responses and meal initiation and the effects of BMI and energy status on this., Design: The experiment had a randomised, cross-over design., Setting and Subjects: Nine normal-weight (age: 33.2+/-4.8 y, BMI: 23.2+/-0.5 kg/m2) and eleven obese (age: 40.8+/- 4.7 y, BMI: 33.2+/-0.8 kg/m2) healthy men were recruited from a pool of volunteers and by advertisements., Interventions: Subjects followed a three-day energy restrictive and a three-day energy balanced diet separated by one month. Each diet was followed by a time-blinded (overnight) stay at the research facility. Subjects received a breakfast (preload) and were instructed to ask for lunch when they felt hungry. Ghrelin, insulin, glucose, free fatty acids, appetite, IMI and energy intake during lunch were assessed., Results: Postprandial decreases in ghrelin (r=-0.54; p<0.05) and the AUC of the ghrelin response (r=-0.57, p=0.01) were associated with the intermeal interval, independent of diet, but in normal weight subjects only. Lunch request was preceded by an increase in ghrelin, reaching at least 93% of fasting values. These preprandial increases in ghrelin were correlated with IMI, after energy restriction only. Ghrelin concentrations but not changes in ghrelin were correlated with appetite., Conclusion: Meal-related changes in ghrelin are correlated with the IMI in normal weight subjects only, independent of diet. Ghrelin concentrations may need to reach a certain threshold level before the next meal is initiated.

Dietary protein plays a role in body weight regulation, partly because of its effects on appetite. The objective was to compare the effects of high or normal casein-, soy-, or whey-protein breakfasts on appetite, specific hormones, amino acid responses and subsequent energy intake. Twenty-five healthy subjects (mean+/-SEMBMI:23.9+/-0.3 kg/m2; age:22+/-1 years) received standardized breakfasts: custards with either casein-, soy, or whey-protein with either 10/55/35 (normal) or 25/55/20 (high)En% protein/carbohydrate/fat in a randomized, single-blind design. Appetite profile (Visual Analogue Scales) and amino acid concentrations were determined for 4 h whereas plasma glucose, insulin, active Glucagon-like Peptide 1 (GLP-1), and active ghrelin concentrations were determined for 3 h; the sensitive moment for lunch was determined. Subjects returned for a second set of experiments and received the same breakfasts, ad lib lunch was offered 180 min later; energy intake (EI) was assessed. At 10En%, whey decreased hunger more than casein or soy (p <0.05), coinciding with higher leucine, lysine, tryptophan, isoleucine, and threonine responses (p<0.05). At 25En% there were no differences in appetite ratings. Whey triggered the strongest responses in concentrations of active GLP-1 (p<0.05) and insulin (p<0.05) compared with casein and/or soy. There were no differences in EI. In conclusion, differences in appetite ratings between different proteins appeared at a normal concentration; at 10En% whey-protein decreased hunger more than casein- or soy-protein. At 25En% whey-protein triggered stronger responses in hormone concentrations than casein- or soy-protein. The results suggest that a difference in appetite ratings between types of protein appears when certain amino acids are above and below particular threshold values.

Although it is possible that binge eating in humans is due to increased responsiveness of orosensory excitatory controls of eating, there is no direct evidence for this because food ingested during a test meal stimulates both orosensory excitatory and postingestive inhibitory controls. To overcome this problem, we adapted the modified sham feeding technique (MSF) to measure the orosensory excitatory control of intake of a series of sweetened solutions. Previously published data showed the feasibility of a "sip-and-spit" procedure in nine healthy control women using solutions flavored with cherry Kool Aid and sweetened with sucrose (0-20%). The current study extended this technique to measure the intake of artificially sweetened solutions in women with bulimia nervosa (BN) and in women with no history of eating disorders. Ten healthy women and 11 women with BN were randomly presented with cherry Kool Aid solutions sweetened with five concentrations of aspartame (0, 0.01, 0.03, 0.08 and 0.28%) in a closed opaque container fitted with a straw. They were instructed to sip as much as they wanted of the solution during 1-minute trials and to spit the fluid out into another opaque container. Across all subjects, presence of sweetener increased intake (p<0.001). Women with BN sipped 40.5-53.1% more of all solutions than controls (p=0.03 for total intake across all solutions). Self-report ratings of liking, wanting and sweetness of solutions did not differ between groups. These results support the feasibility of a MSF procedure using artificially sweetened solutions, and the hypothesis that the orosensory stimulation of MSF provokes larger intake in women with BN than controls.

There is a widely held view that hunger prompts feeding to ensure energy needs are met, while thirst cues drinking to address hydration requirements. However, recent changes in the nature of the food supply and eating patterns have raised questions about the functionality of these relationships with respect to maintaining energy balance. The increasing consumption of energy-yielding beverages and foods with diluted energy density, through the use of ingredients such as high-intensity sweeteners and fat replacers, poses new challenges to presumed homeostatic energy regulatory mechanisms. This review draws on findings from a recent observational study and other published evidence to explore whether shifts of food composition and use patterns may be disrupting relationships between thirst, hunger, drinking, and eating, resulting in positive energy balance (e.g., drinking low satiety, energy-yielding beverages in response to hunger). The observational study entailed collecting hourly appetitive ratings and dietary recalls from 50 adults for seven consecutive days. These data reveal a clear bimodal daily hunger pattern, whereas thirst is stronger and more stable throughout the day. Further, approximately 75% of fluid intake occurs peri-prandially, with the majority derived from energy-yielding beverages. While there is published evidence that drinking is responsive to feeding, support for the view that drinking is the more tightly regulated behavior is stronger. Our data indicates that, due to a number of plausible factors, neither absolute values nor changes of hunger or thirst are strong predictors of energy intake. However, it is proposed that stable, high thirst facilitates drinking, and with the increased availability and use of energy-yielding beverages that have low satiety properties, can promote positive energy balance. There are marked individual differences in mean daily hunger and thirst ratings with unknown implications for energy balance.

A growing body of research on caloric restriction (CR) in many species of laboratory animals suggests that underfeeding leads to better health and longevity in the calorically-restricted animal (e.g., see [[34]. J.P. Pinel, S. Assanand and D.R. Lehman, (2000). Hunger, eating and ill health. Am Psychol, 55, 1105-1116.], for a review). Although some objections have been raised by scientists concerned about negative psychological and behavioral sequelae of such restriction, advocates of CR continue to urge people to adopt sharply reduced eating regimes in order to increase their longevity. Yet very few people are even attempting to reap the benefits of such restriction. The present paper explores one factor that may deter many humans from drastically reducing their food consumption--the presence of abundant, attractive food cues in the environment. Research on the influence of food cues on food-related behaviors is reviewed to demonstrate that the presence of food cues makes restriction of intake more difficult.

Flavor-flavor and flavor-nutrient associations can modify liking for a flavor CS, while flavor-flavor associations can also modify the sensory experience of the trained flavor. Less is known about how these associations modify behavioral responses to the trained CS. To test this, 60 participants classified as sweet likers were divided into five training conditions with a novel flavor CS. In the flavor-flavor only condition, participants consumed the target CS in a sweetened, low-energy form, with energy (maltodextrin) but no sweetness added in the flavor-nutrient only condition and both energy and sweetness (sucrose) in the combined flavor-flavor, flavor-nutrient condition. Comparison groups controlled for exposure to the CS, and repeat testing. Training was conducted in a hungry state on four non-consecutive days. To test for acquired changes in evaluation and intake, the flavor CS was processed into a low-energy sorbet, which was evaluated and consumed ad libitum on test days before and after training. Liking for the flavor CS increased only in the sucrose-sweetened condition, but intake increased significantly in both high-energy conditions. In contrast, rated sweetness of the sorbet increased in both sucrose-sweetened and aspartame-sweetened conditions. These findings suggest that liking changes were maximal when flavor-flavor and flavor-nutrient associations co-occurred, but that behavioral changes were specific to flavor-nutrient associations.

Release of peptide YY(3-36) (PYY(3-36)) has been proposed to contribute to postprandial satiety. Using a randomized, double-blind design, we examined the effects of a 417 kcal beverage with 95% of the calories from long-chain fatty acids compared to a 21 kcal lipid-free control beverage on the temporal profiles of total plasma PYY levels and appetite ratings in 12 normal-weight human subjects. Ratings were taken before ingestion of the beverage and 15, 30, 60, 120, and 180 min later. Blood samples were taken from the subjects when ratings were made. The lipid beverage increased plasma PYY relative to the control beverage at 60-180 min after ingestion. Subjects were divided into High and Low PYY groups (N=6 in each group) on the basis of a median split. In the High PYY group, the lipid beverage was more effective in suppressing hunger and enhancing satiety than in the Low PYY group, in which the lipid beverage had no effects on appetite. Within the High PYY group, changes in mean relative hunger suppression (changes in hunger specifically attributable to the lipid load) across the 3-h test closely paralleled changes in plasma PYY after ingestion of the lipid beverage relative to the control beverage. The close temporal correspondence between these variables supports the proposed role of this peptide in the intermediate-term control of intake, possibly acting to regulate appetite during the intermeal interval.

A novel flavour may become liked if it is presented repeatedly and in combination with a second flavour that is already liked. Conceptually, this 'flavour-flavour learning' is important, because it can account for many of our everyday food and flavour preferences. However, relatively little is known about the underlying process because learning paradigms have lacked reliability. Based on previous research we explored whether learning is determined by three variables; i) hunger state, ii) demand and contingency awareness, and iii) dietary restraint. Participants (male n=15/female n=15) consumed three different and novel-tasting fruit teas. One of the teas had a non-caloric sweetener added (CS+) and two were unsweetened (CS-). Before and after this training the participants ranked their preference for unsweetened versions of the three teas. We found that the training increased preference for the CS+ relative to the CS- teas. However, this effect was only found in hungry participants. We also found little evidence that learning was related to whether the participants could identify (recognition test) the specific tea that had been sweetened during training, suggesting that the underlying process is automatic and it operates outside conscious awareness. Learning was not predicted by dietary restraint (measured using the DEBQ-R scale). Together, these findings provide further evidence for a linkage between flavour-flavour learning and flavour-nutrient learning.

Anticipatory hunger is a learnt increase in intake of food having a flavour or texture that predicts a long fast. This learning was studied in rats trained on a single food or a choice between protein-rich and carbohydrate-rich foods, presented for 1.5 h after 3 h without maintenance food at the start of the dark phase. Eight training cycles provided a pseudo-random sequence of 3 h and 10 h post-prandial fasts with a day on maintenance food between each training fast. The measure of anticipatory hunger is the difference over one 4-day cycle between the intake of test food having an odour predictive of the longer fast (TL) and intake of food with an odour cuing to the shorter fast (TS). Previous experiments showed that conditioning of preference for the odour before the shorter fast competes with learning to avoid hunger during the longer fast (anticipatory hunger), generating a cubic or quartic contrast. TL minus TS showed a strong cubic trend over 8 training cycles with both single and choice meals. There was a switch from preference for the short-fast odour at cycle 2 (TL-TS=-0.86 g) to a peak of anticipatory hunger at cycle 6 (TL-TS=1.57 g). We conclude that anticipatory hunger is learnt when a choice is given between protein-rich and carbohydrate-rich foods as well as on a single food. In addition, since anticipatory hunger extinguishes itself, such learning improves on negative-feedback homeostasis with a feed-forward "hyper-homeostatic" mechanism.

An increasing proportion of human food consumption appears to be driven by pleasure, not just by the need for calories. In addition to its effects on body mass and health, the food environment in affluent societies may be creating an appetitive counterpart to the psychological effects of other hedonically-driven activities such as drug use and compulsive gambling. This phenomenon is referred to here as "hedonic hunger." Animal literature is reviewed indicating that brain-based homeostatic and hedonic eating motives overlap but are nonetheless dissociable. In humans there is evidence that obese individuals prefer and consume high palatability foods more than those of normal weight. Among normal weight individuals it has long been assumed that the appetitive anomalies associated with restrained eating are due to diet-induced challenges to the homeostatic system, but we review evidence suggesting that they more likely stem from hedonic hunger (i.e., eating less than wanted rather than less than needed). Finally, a recently-developed measure (the Power of Food Scale; PFS) of individual differences in appetitive responsiveness to rewarding properties of the food environment is described. Preliminary evidence indicates that the PFS is reliable and valid and is related to clinically-relevant variables such as food cravings and binge eating. This measure, combined with environmental manipulations of food availability and palatability, may constitute a useful approach to studying hedonic hunger.

Experimentally-induced hyperglycemia by prolonged glucose infusion allows investigation of the effects of sustained stimulation of the pancreatic beta-cell on insulin secretion and sensitivity. Hormonal responses to a meal following prolonged glucose infusions have not been investigated. To determine if a 48-h glucose infusion alters hormonal responses to a test meal as well as food intake and hunger in normal weight individuals, 16 subjects (8 men, 8 women, age 18-30 years, mean BMI=21.7+/-1.6 kg/m2) were infused for 48 h with either saline (50 ml/h) or 15% glucose (200 mg/m2/min). Subjects ingested a 600 kcal mixed nutrient meal 3 h after infusion termination. Blood samples were taken during the 48 h and for 4 h following food ingestion. The 48-h glucose infusion elicited a metabolic profile of a glucose intolerant obese subjects, with increased plasma glucose, insulin and leptin (all P<0.01) and increased HOMA-IR (P<0.001). During meal ingestion, early insulin secretion was increased (P<0.05) but post-prandial glucose (P<0.01) and insulin (P<0.01) excursions were lower following the glucose infusion. Post-prandial plasma triglyceride concentrations were increased after glucose compared with saline. Food intake and hunger ratings were not different between the two conditions. Plasma leptin levels were inversely correlated with hunger (P<0.03) in both conditions and with food intake (P<0.003) during the glucose condition only. Thus, a 48-h glucose infusion does not impair post-prandial hormonal responses, alter food intake or hunger in normal weight subjects. The glucose-induced increases in plasma leptin result in a stronger inverse relationship between plasma leptin and hunger as well as food intake. These data are the first to demonstrate a relationship between leptin and hunger in normal weight, non-calorically restricted human subjects.

Explicit cues associated with food consumption when hunger prevails will enhance eating when they are subsequently presented under conditions of satiety. Here we examined whether contextual conditioned stimuli (CSs) paired with consumption of food pellets while rats were food-deprived would enhance consumption of this food in rats that were not food-deprived. The conditioning context enhanced rats' consumption of the training food, but it did not change their consumption of the familiar, lab chow. These results show that the contextual CSs, like discrete cues, could modulate food consumption in a CS-potentiated eating paradigm. Furthermore, the data suggest that CS-potentiation of eating does not induce a general motivation to eat, akin to hunger, but instead more likely produces a more specific motivational state, akin to craving.

Berridge's model (e.g. [Berridge KC. Food reward: Brain substrates of wanting and liking. Neurosci Biobehav Rev 1996;20:1-25.; Berridge KC, Robinson T E. Parsing reward. Trends Neurosci 2003;26:507-513.; Berridge KC. Motivation concepts in behavioral neuroscience. Physiol Behav 2004;81:179-209]) outlines the brain substrates thought to mediate food reward with distinct 'liking' (hedonic/affective) and 'wanting' (incentive salience/motivation) components. Understanding the dual aspects of food reward could throw light on food choice, appetite control and overconsumption. The present study reports the development of a procedure to measure these processes in humans. A computer-based paradigm was used to assess 'liking' (through pleasantness ratings) and 'wanting' (through forced-choice photographic procedure) for foods that varied in fat (high or low) and taste (savoury or sweet). 60 participants completed the program when hungry and after an ad libitum meal. Findings indicate a state (hungry-satiated)-dependent, partial dissociation between 'liking' and 'wanting' for generic food categories. In the hungry state, participants 'wanted' high-fat savoury>low-fat savoury with no corresponding difference in 'liking', and 'liked' high-fat sweet>low-fat sweet but did not differ in 'wanting' for these foods. In the satiated state, participants 'liked', but did not 'want', high-fat savoury>low-fat savoury, and 'wanted' but did not 'like' low-fat sweet>high-fat sweet. More differences in 'liking' and 'wanting' were observed when hungry than when satiated. This procedure provides the first step in proof of concept that 'liking' and 'wanting' can be dissociated in humans and can be further developed for foods varying along different dimensions. Other experimental procedures may also be devised to separate 'liking' and 'wanting'.

Eating in competition with other tasks has been shown to increase food intake, particularly when tasks are cognitively demanding. To test the hypothesis that social facilitation of eating occurs, in part, as a function of distraction which impairs the ability to self-monitor, eating with others was compared with eating alone or in front of the television. Using a repeated measure within-subjects design, thirty-seven participants (21 males) visited the laboratory 4 times to eat a buffet-style lunch ad libitum. All eating episodes were filmed. Energy intake (EI) was measured when participants ate alone (A), ate alone while watching TV (B), ate with two same sex strangers (C), and ate with two same sex friends (D) in a counterbalanced order. EI was significantly enhanced by presence of familiar others (D: 4565+/-272 kJ, p < 0.001) and watching TV (B: 4350+/-252 kJ, p < 0.05) compared to baseline (A: 3861+/-200 kJ). Length of eating episode correlated significantly (p < 0.05) with EI, however, amount of time spent eating and looking at food differed by condition with a greater percentage of time focussed on food during baseline (p < 0.001). Eating with friends increased EI by 18% and eating in front of the TV increased EI by 14% relative to baseline. Engaging in conversation or watching TV draws attention away from the eaten food and can stimulate food intake. However, since eating with strangers also drew attention away from food but did not result in increased intake, social facilitation effects are not simply due to distraction. Thus food intake can be enhanced when attention to food and self-monitoring are impaired during distraction, however, this effect is moderated when eating with strangers.

Television viewing (TVV) has been linked with obesity, possibly through increased sedentary behavior and/or through increased ingestion during TVV. The proposition that TVV causes increased feeding, however, has not been subjected to experimental verification until recently. Our objective was to determine if the amount eaten of two familiar, palatable, high-density foods (pizza and macaroni and cheese) was increased during a 30-min meal when watching TV. In a within-subjects design, one group of undergraduates (n = 10) ate pizza while watching a TV show of their choice for one session and when listening to a symphony during the other session. A second group of undergraduates (n = 10) ate macaroni and cheese (M&C). TVV increased caloric intake by 36% (one slice on average) for pizza and by 71% for M&C. Eating patterns also differed between conditions. Although the length of time to eat a slice of pizza remained stable between viewing conditions, the amount of time before starting another slice was shorter during TVV. In contrast, M&C was eaten at a faster rate and for a longer period of time during TVV. Thus, watching television increases the amount eaten of high-density, palatable, familiar foods and may constitute one vector contributing to the current obesity crisis.

Broiler breeder chickens show apparently abnormal behaviours when subjected to routine quantitative food restriction during rearing. By using a combination of videorecording and radiotelemetry, this experiment addressed the question of whether such behaviours are associated with de-arousal. In each of 2 years, 3 female chickens had radiotelemetry devices (Data Sciences) implanted surgically at 12 weeks of age, for measuring putative physiological indices of arousal (heart rate, blood pressure, body temperature, telencephalic EEG). Subsequently, when caged individually and moving freely, they were monitored over 2 days when their daily food ration (60 g pellets provided at 0900 h) was all eaten in <10 min. Their behaviour (nine categories) and arousal indices were recorded in every minute during the photoperiod (0700 to 1900 h), using special computer software for videorecording (Noldus) and radiotelemetry (Dataquest LabPRO) analyses. Most time was spent in behaviour categories stand, push bar and feeder directed. Heart rate, blood pressure, body temperature, and relative powers in delta (1-4 Hz) and theta (4-8 Hz) frequency bands of the EEG power spectrum were all highest during feeder directed, whereas heart rate, temperature and delta EEG were all lowest during stand. Judging from significant correlation coefficients between times spent in different behaviours and corresponding physiological variables, across the day, and between ranked mean values of the 6 birds, other trends were also evident. For example, total time spent in all (non-food directed) oral behaviours was related positively to an index of de-arousal (slow wave EEG) and negatively to an index of arousal (heart rate). Collectively, however, these results provide apparently conflicting evidence of both arousal and de-arousal being associated with every behaviour analysed. This conclusion is explicable if abnormal behaviours are related to arousal in a homeostatic way [Savory, C.J., Kostal, L. Temporal patterning of oral stereotypies in restricted-fed fowls: 1. Investigations with a single daily meal. Int. J. Comp. Psychol. 1996, 9:117-139.], being both stimulated by it and reducing it.

Recent evidence indicates that rats can learn to avoid aversive consequences of several hours of food deprivation by eating more of food having orosensory characteristics that predict a protracted fast. Two new studies tested if macronutrient composition of a flavoured meal before the reinforcing fast influences this acquisition of anticipatory hunger/satiety in a smooth-brained mammal. In one study, female Sprague-Dawley rats were trained for 11 cycles of 4 days with experimental meals of either carbohydrate or protein flavoured with either grape or cherry, with one odour followed by a 3-h fast and the other by 10 h of food deprivation. Both nutrient groups acquired anticipatory hunger. Then that learnt increase in meal size started to extinguish the hunger-avoidance response to the longer fast. The other study tested if this finding extended to experimental meals that combined carbohydrate and protein, and had vanilla or chicken flavours, to fasts of 4 and 12 h and to male rats as well as females within a training period of 6 cycles of 4 days. Evidence of anticipatory hunger early in training was clear only in the males. The combined results from the two experiments indicate that either carbohydrate or protein is sufficient for negative reinforcement of flavour-specific anticipatory hunger when the shorter fast lasts for 3 h. This food-discriminative anticipatory adjustment of meal size could be an automatically learnt part of hunger management for socially scheduled eating in human beings.

The factors that regulate food intake and satiation are complex; it has been suggested that signals arising from the small intestine and the stomach play an important role. It is still unknown, to what extent pure mechanical distension of the gastric fundus and antrum can alter food intake. Our aim was therefore to investigate whether transient gastric fundus and antrum distension applied prior to meal ingestion can trigger satiation in healthy humans. Two sequential, randomized, double-blind, four-period cross-over designed studies were performed in 24 healthy male volunteers: (1) 12 subjects underwent four intragastric balloon distension experiments of the fundus (0, 400, 600, 800 ml) before a standard meal intake; (2) 12 subjects underwent intragastric balloon distension experiments of the antrum under the following conditions: 0 ml balloon distension of the antrum plus intraduodenal (ID) saline or ID fat, and 300 ml antrum distension plus ID saline or ID fat. Shortly after the distension period, subjects were free to eat and drink as much as they wished. Neither gastric fundus nor antrum distension showed a reduction in calorie intake. Distending the fundus affected the mean Visual Analogue Scale (VAS) in the premeal period: subjects experienced a reduced degree of hunger and a concomitant feeling of fullness, but the effect was only apparent during distension with a volume of 600 ml or even 800 ml. Cholecystokinin (CCK) and peptide YY (PYY) were not altered by gastric distension. Transient pure mechanical distension of the fundus or the antrum prior to a meal does not trigger satiation.

Prior exposure to hypoglycemia impairs neuroendocrine counterregulatory responses (CRR) during subsequent hypoglycemia. Defective CRR to hypoglycemia is a component of the clinical syndrome hypoglycemia-associated autonomic failure (HAAF). Hypoglycemia also potently stimulates food intake, an important behavioral CRR. Because the increased feeding response to hypoglycemia is behavioral and not hormonal, we hypothesized that it may be regulated differently with recurrent bouts of hypoglycemia. To test this hypothesis, we simultaneously evaluated neuroendocrine CRR and food intake in rats experiencing one or three episodes of insulin-induced hypoglycemia. As expected, recurrent hypoglycemia significantly reduced neuroendocrine hypoglycemic CRR. Epinephrine (E), norepinephrine (NE) and glucagon responses 120 min after insulin injection were significantly reduced in recurrent hypoglycemic rats, relative to rats experiencing hypoglycemia for the first time. Despite these neuroendocrine impairments, food intake was significantly elevated above baseline saline intake whether rats were experiencing a first (hypoglycemia: 3.4+/-0.4 g vs. saline: 0.94+/-0.3 g, P<0.05) or third hypoglycemic episode (hypoglycemia: 3.8+/-0.3 g vs. saline: 1.2+/-0.3 g, P<0.05). These findings demonstrate that food intake elicited in response to hypoglycemia is not impaired as a result of recurrent hypoglycemia. Thus, neuroendocrine and behavioral (stimulation of food intake) CRR are differentially regulated by recurrent hypoglycemia experience.

Objective: The purpose of the study was to examine the effect of energy density and food weight (volume) on subsequent intake., Design: Sixteen lean men were each studied four times during a 2-d protocol at the Rowett's Human Nutrition Unit. On day 1, subjects were fed a mandatory diet at 1.6 x resting metabolic rate (RMR). On day 2, during the mandatory morning period (08.30-12.30) subjects consumed a fixed breakfast (08.30) plus a snack (10.30) in one of four treatments [with values in weight (kg), ED (kJ/100g), Energy (MJ)]: (i) zero intake, 0:0:0 (ii) low energy density (LED), 0.615: 400: 2.46; (iii) high energy density (HED), 0.615: 800: 4.92; (iv) 2 x LED, 1.225: 400: 4.91. From 12.30, throughout the remainder of the day, subjects had ad libitum access to 15 high-protein, 15 high-fat and 15 high-carbohydrate foods. Motivation to eat was tracked hourly using 100 mm line scales., Results: ANOVA showed subjects were hungrier after the zero and LED treatments in the mandatory period (p<0.001). Lunch time EI was 5.0, 3.1, 4.2 and 3.2 MJ on the zero, HED, LED and 2 x LED treatments, respectively (p<0.001). Total ad libitum EI was 11.7, 9.6, 10.3 and 9.5 MJ/d, respectively (p=0.033). Total ad libitum plus mandatory intakes amounted to 11.7, 14.5, 12.6 and 14.4 MJ/d, respectively (p=0.001). Corresponding food intakes were 2.18, 2.39, 2.51 and 3.06 kg/d, respectively (p<0.001)., Conclusions: The present study showed that subjects respond to both the amount of food eaten in the morning and to the energy density of those foods. However, compensation was only partial and short-term. Subjects only compensated EI by approximately 40% and that compensation only occurred at the next meal.