Presenting a food in multiple smaller units increases expected satiety

Presentation of the same amount of a food in multiple smaller units (‘segmentation’) has been shown to reduce food intake and increase estimates of the amount of food consumed. However, this effect has been demonstrated for ad libitum food intake only. In the majority of cases, meals are not consumed ad libitum, but are pre-selected and consumed in their entirety, Expected satiety (ES; the anticipated capacity of a portion of food to relieve hunger between meals) is an excellent predictor of portion size selection. This study tested the hypothesis that segmentation increases ES. It was also hypothesised that perceived volume (PV) may account for the relationship between segmentation and ES. Sixty-eight participants made computer-based ES and PV judgments for equicaloric portions of three test foods (salted peanuts, spaghetti Bolognese, and chicken tikka masala), which were presented in either a single unit or as multiple smaller units (three or six units). Results revealed a consistent effect of segmentation on ES - foods presented in multiple smaller units were expected to deliver significantly greater satiety than when presented in a single unit (p < 0.005). Furthermore, results indicated that the effect of segmentation on ES was attributable to an increase in PV. ES plays an important role in determining the portion sizes that people select. Therefore, awareness of the effect of segmentation on ES may help to inform the design of foods that confer benefits for healthy weight maintenance.

Disinhibited eating mediates differences in attachment insecurity between bariatric surgery candidates/recipients and lean controls

Previous research has shown that attachment anxiety is a good predictor of body mass index. This relationship is significantly mediated by disinhibited (over-) eating and is likely to reflect a specific form of affect regulation. This study explored whether obese bariatric surgery candidates (BSC; N=34) and bariatric surgery recipients (BSR; N=15) would show higher levels of attachment insecurity (higher attachment anxiety and/or higher attachment avoidance) than a group of age and gender-matched lean controls (N=54). Mediation analyses showed that compared to lean controls (M=2.96, SE=0.1), both BSC (M=3.5, SE=0.2) and BSR (M=3.4, SE=0.2) groups had a more insecure attachment orientation. These relationships were significantly mediated by disinhibited eating (BSC: lower limit confidence interval (LLCI)=0.06 and upper limit confidence interval (ULCI)=0.62; BSR: LLCI=0.02 and ULCI=0.76). There was no such relationship when the BSC and BSR groups were compared (LLCI=−0.15 & ULCI=0.3). These observations suggest that attachment insecurity may be a risk factor for obesity and bariatric surgery because of associated disinhibited eating. Moreover, these factors may be important to consider when bariatric surgery results in poor outcomes.

Food portion size area mediates energy effects on expected anxiety in anorexia nervosa

A study in which adolescent patients with anorexia nervosa (n = 24) rated their expected food-anxiety in response to images of portions of food (potatoes, rice pizza, and M&Ms) showed that lower energy-dense foods elicited higher expected anxiety per kilocalorie than higher energy-dense foods. However, the area of the portion sizes could be an unmeasured variable driving the anxiety response. To test the hypothesis that area mediates the effects of energy content on expected anxiety, the same images of portions were measured in area (cm2), and standardized values of expected anxiety were regressed from standardized values of energy and area of portions. With regression of expected anxiety from portion size in area, M&Ms, which had the highest energy density of the four foods, elicited the highest expected anxiety slope (β = 1.75), which was significantly different from the expected anxiety slopes of the other three foods (β range = 0.67 - 0.96). Area was confirmed as a mediator of energy effects from loss of significance of the slopes when area was added to the regression of expected anxiety from energy x food. When expected anxiety was regressed from food, area, energy and area by energy interaction, area accounted for 5.7 times more variance than energy, and β for area (0.7) was significantly larger (by 0.52, SE = 0.15, t = 3.4, p = 0.0007) than β for energy (0.19). Area could be a learned cue for the energy content of food portions, and thus, for weight gain potential, which triggers anxiety in patients with anorexia nervosa.

Individual variability in preference for energy-dense foods fails to predict child BMI percentile

Many studies show that higher dietary energy density is associated with greater body weight. Here we explored two propositions: i) that child BMI percentile is associated with individual differences in children's relative preference for energy-dense foods, ii) that child BMI percentile is associated with the same individual differences between their parents. Child-parent dyads were recruited from a local interactive science center in Bristol (UK). Using computerized tasks, participants ranked their preference and rated their liking for a range of snack foods that varied in energy density. Children (aged 3–14 years, N = 110) and parents completed the tasks for themselves. Parents also completed two further tasks in which they ranked the foods in the order that they would prioritize for their child, and again, in the order that they thought their child would choose. Children preferred (t(109) = 3.91, p < 0.001) and better liked the taste of (t(109) = 3.28, p = 0.001) higher energy-dense foods, and parents correctly estimated this outcome (t(109) = 7.18, p < 0.001). Conversely, lower energy-dense foods were preferred (t(109) = − 4.63, p < 0.001), better liked (t(109) = − 2.75, p = 0.007) and served (t(109) = − 15.06, p < 0.001) by parents. However, we found no evidence that child BMI percentile was associated with child or parent preference for, or liking of, energy-dense foods. Therefore, we suggest that the observed relationship between dietary energy density and body weight is not explained by individual differences in preference for energy density.

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Higher dietary energy density (ED) is associated with greater body weight.

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A novel, computerized task was implemented to assess preference for ED.

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Children's and parent's relative preferences for ED were measured.

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Variation in relative ED preference was not associated with child BMI percentile.

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Alternate explanations of the association between dietary ED and BMI are discussed.

Modulation of sweet preference by the actual and anticipated consequences of eating

Previous research has shown that non-human animals exhibit an inverted-U pattern of sweet preference, with consumption increasing across moderate levels of sweetness and then declining for high levels of sweetness. In rodents, this pattern reflects an avoidance of the postingestive effects of consuming energy-dense sugar solutions (conditioned satiation). Here, we examined whether humans also adjust their preferences to compensate for the anticipated energy content/satiating outcomes of consuming sweetened foods. In two experiments (each N = 40), participants were asked to taste and imagine eating small (15 g) and large (250 g) portions of five novel desserts that varied in sweetness. Participants evaluated the desserts' expected satiety, expected satiation, and expected sickliness. A measure of estimated energy content was also derived using a computerized energy compensation test. This procedure was completed before and after consuming a standard lunch. Across both experiments, results confirmed that participants preferred a less sweet dessert when asked to imagine eating a large versus a small portion, and when rating the dessert in a fed versus fasted state. We also obtained evidence that participants anticipated more energy from the sweeter desserts (even in Experiment 2 when half of the participants were informed that the desserts were equated for energy content). However we found only partial evidence for anticipated satiation-expected sickliness was related systematically to increases in sweetness, but expected satiation and expected satiety were only weakly influenced. These findings raise questions about the role of sweetness in the control of food intake (in humans) and the degree to which 'sweet-calorie learning' occurs in complex dietary environments where sweetness may actually be a poor predictor of the energy content of foods.

Large Portions Encourage the Selection of Palatable Rather Than Filling Foods

BACKGROUND

Portion size is an important driver of larger meals. However, effects on food choice remain unclear.

OBJECTIVE

Our aim was to identify how portion size influences the effect of palatability and expected satiety on choice.

METHODS

In Study 1, adult participants (n = 24, 87.5% women) evaluated the palatability and expected satiety of 5 lunchtime meals and ranked them in order of preference. Separate ranks were elicited for equicaloric portions from 100 to 800 kcal (100-kcal steps). In Study 2, adult participants (n = 24, 75% women) evaluated 9 meals and ranked 100-600 kcal portions in 3 contexts (scenarios), believing that 1) the next meal would be at 1900, 2) they would receive only a bite of one food, and 3) a favorite dish would be offered immediately afterwards. Regression analysis was used to quantify predictors of choice.

RESULTS

In Study 1, the extent to which expected satiety and palatability predicted choice was highly dependent on portion size (P < 0.001). With smaller portions, expected satiety was a positive predictor, playing a role equal to palatability (100-kcal portions: expected satiety, β: 0.42; palatability, β: 0.46). With larger portions, palatability was a strong predictor (600-kcal portions: β: 0.53), and expected satiety was a poor or negative predictor (600-kcal portions: β: -0.42). In Study 2, this pattern was moderated by context (P = 0.024). Results from scenario 1 replicated Study 1. However, expected satiety was a poor predictor in both scenario 2 (expected satiety was irrelevant) and scenario 3 (satiety was guaranteed), and palatability was the primary driver of choice across all portions.

CONCLUSIONS

In adults, expected satiety influences food choice, but only when small equicaloric portions are compared. Larger portions not only promote the consumption of larger meals, but they encourage the adoption of food choice strategies motivated solely by palatability.

Variation in the Oral Processing of Everyday Meals Is Associated with Fullness and Meal Size; A Potential Nudge to Reduce Energy Intake?

Laboratory studies have demonstrated that experimental manipulations of oral processing can have a marked effect on energy intake. Here, we explored whether variations in oral processing across a range of unmodified everyday meals could affect post-meal fullness and meal size. In Study 1, female participants (N = 12) attended the laboratory over 20 lunchtime sessions to consume a 400-kcal portion of a different commercially available pre-packaged meal. Prior to consumption, expected satiation was assessed. During each meal, oral processing was characterised using: (i) video-recordings of the mouth and (ii) real-time measures of plate weight. Hunger and fullness ratings were elicited pre- and post-consumption, and for a further three hours. Foods that were eaten slowly had higher expected satiation and delivered more satiation and satiety. Building on these findings, in Study 2 we selected two meals (identical energy density) from Study 1 that were equally liked but maximised differences in oral processing. On separate days, male and female participants (N = 24) consumed a 400-kcal portion of either the "fast" or "slow" meal followed by an ad libitum meal (either the same food or a dessert). When continuing with the same food, participants consumed less of the slow meal. Further, differences in food intake during the ad libitum meal were not compensated at a subsequent snacking opportunity an hour later. Together, these findings suggest that variations in oral processing across a range of unmodified everyday meals can affect fullness after consuming a fixed portion and can also impact meal size. Modifying food form to encourage increased oral processing (albeit to a lesser extent than in experimental manipulations) might represent a viable target for food manufacturers to help to nudge consumers to manage their weight.

Sensory specific satiety: More than 'just' habituation?

Sensory specific satiety (SSS) describes the decline in pleasantness associated with a food as it is eaten relative to a food that has not been eaten (the ‘eaten’ and ‘uneaten’ foods, respectively). The prevailing view is that SSS is governed by habituation. Nevertheless, the extent to which SSS results solely from this ‘low-level’ process remains unclear. Three experiments were conducted to explore the hypothesis that ‘top-down’ cognitive activity affects the expression of SSS; specifically, we manipulated participants' expectations about whether or not they would have access to alternative test foods (uneaten foods) after consuming a test meal (eaten food). This manipulation was motivated by ‘Commodity Theory,’ which describes the relative increase in value of a commodity when it becomes unavailable. We tested the hypothesis that a decline in the pleasantness and desire to eat the eaten food is exaggerated when uneaten foods are unavailable to participants. None of our findings supported this proposition – we found no evidence that SSS is dependent on top-down processes associated with the availability of other uneaten test foods.

Elasticity in portion selection is predicted by severity of anorexia and food type in adolescents

The size of portions that people select is an indicator of underlying mechanisms controlling food intake. Fears of eating excessive portions drive down the sizes of portions patients with anorexia nervosa (AN) can tolerate eating significantly below those of healthy controls (HC) (Kissileff et al., 2016). To determine whether patients with AN will also reduce the sizes of typical or ideal portions below those of controls, ANOVA was used to compare maximum tolerable, typical, and ideal portions of four foods (potatoes, rice, pizza, and M&M's) in the same group of 24 adolescent AN patients and 10 healthy adolescent controls (HC), on which only the maximal portion data were previously reported. Typical and ideal portion sizes did not differ on any food for AN, but for HC, typical portions sizes (kcals) became larger than ideal as the energy density of the food increased, and were significant for the most energy dense food. Ideal portions of low energy dense foods were the same for AN as for in HC. There was a significant 3-way (group × food × portion type) interaction, such that HC selected larger maximum than typical portions only for pizza. We therefore proposed that individuals of certain groups, depending on the food, can be flexible in the amounts of food chosen to be eaten. We call this difference between maximum-tolerable, and typical portion sizes selected "elasticity." Elasticity was significantly smaller for AN patients compared to HC for pizza and was significantly inversely correlated with severity of illness. This index could be useful for clinical assessment of AN patients, and those with eating problems such as in obesity and bulimia nervosa and tracking their response to treatment.

Visual exposure to large and small portion sizes and perceptions of portion size normality: Three experimental studies

Portion sizes of many foods have increased in recent times. In three studies we examined the effect that repeated visual exposure to larger versus smaller food portion sizes has on perceptions of what constitutes a normal-sized food portion and measures of portion size selection. In studies 1 and 2 participants were visually exposed to images of large or small portions of spaghetti bolognese, before making evaluations about an image of an intermediate sized portion of the same food. In study 3 participants were exposed to images of large or small portions of a snack food before selecting a portion size of snack food to consume. Across the three studies, visual exposure to larger as opposed to smaller portion sizes resulted in participants considering a normal portion of food to be larger than a reference intermediate sized portion. In studies 1 and 2 visual exposure to larger portion sizes also increased the size of self-reported ideal meal size. In study 3 visual exposure to larger portion sizes of a snack food did not affect how much of that food participants subsequently served themselves and ate. Visual exposure to larger portion sizes may adjust visual perceptions of what constitutes a 'normal' sized portion. However, we did not find evidence that visual exposure to larger portions altered snack food intake.

Computerized measurement of anticipated anxiety from eating increasing portions of food in adolescents with and without anorexia nervosa: Pilot studies

Dieting and excessive fear of eating coexist in vulnerable individuals, which may progress to anorexia nervosa [AN], but there is no objective measure of this fear. Therefore, we adapted a computer program that was previously developed to measure the satiating effects of foods in order to explore the potential of food to induce anxiety and fear of eating in adolescent girls. Twenty four adolescents (AN) and ten healthy controls without eating disorders rated pictures of different types of foods in varying sized portions as too large or too small and rated the expected anxiety of five different portions (20-320 kcal). Two low energy dense (potatoes and rice) and two high energy dense (pizza and M&Ms) foods were used. The regression coefficient of line lengths (0-100 mm) marked from "No anxiety" to "this would give me a panic attack", regressed from portions shown, was the measure of "expected anxiety" for a given food. The maximum tolerated portion size [kcal] (MTPS), computed by method of constant stimulus from portions shown, was significantly smaller for high energy dense foods, whereas the expected anxiety response was greater, for all foods, for patients compared to controls. For both groups, expected anxiety responses were steeper, and maximum tolerated portion sizes were larger, for low, than high, energy dense foods. Both maximum tolerated portion size and expected anxiety response were significantly predicted by severity of illness for the patients. Those who had larger maximum tolerated portion sizes had smaller anticipated anxiety to increasing portion sizes. Visual size had a greater influence than energy content for these responses. This method could be used to quantify the anxiety inducing potential of foods and for studies with neuro-imaging and phenotypic clarifications.

Effects of eating rate on satiety: A role for episodic memory?

Eating slowly is associated with a lower body mass index. However, the underlying mechanism is poorly understood. Here, our objective was to determine whether eating a meal at a slow rate improves episodic memory for the meal and promotes satiety. Participants (N=40) consumed a 400ml portion of tomato soup at either a fast (1.97ml/s) or a slow (0.50ml/s) rate. Appetite ratings were elicited at baseline and at the end of the meal (satiation). Satiety was assessed using; i) an ad libitum biscuit 'taste test' (3h after the meal) and ii) appetite ratings (collected 2h after the meal and after the ad libitum snack). Finally, to evaluate episodic memory for the meal, participants self-served the volume of soup that they believed they had consumed earlier (portion size memory) and completed a rating of memory 'vividness'. Participants who consumed the soup slowly reported a greater increase in fullness, both at the end of the meal and during the inter-meal interval. However, we found little effect of eating rate on subsequent ad libitum snack intake. Importantly, after 3h, participants who ate the soup slowly remembered eating a larger portion. These findings show that eating slowly promotes self-reported satiation and satiety. For the first time, they also suggest that eating rate influences portion size memory. However, eating slowly did not affect ratings of memory vividness and we found little evidence for a relationship between episodic memory and satiety. Therefore, we are unable to conclude that episodic memory mediates effects of eating rate on satiety.

Energy-dense snacks can have the same expected satiation as sugar-containing beverages

Sugar-sweetened beverages (SSBs) are thought to be problematic for weight management because energy delivered in liquid form may be less effective at suppressing appetite than solid foods. However, little is known about the relative 'expected satiation' (anticipated fullness) of SSBs and solid foods. This is relevant because expected satiation is an important determinant of portion selection and energy intake. Here, we used a method of constant stimuli to assess the expected satiation of test meals that were presented in combination with different caloric and non-caloric beverages (500 ml) (Experiment 1 and 2), as well as with high-energy solid snack foods (Experiment 2). All energy-containing beverages and snack foods were presented in 210 kcal portions. Both experiments found that expected satiation was greater for meals containing caloric versus non-caloric beverages (201.3 ± 17.3 vs. 185.4 ± 14.1 kcal in Experiment 2; p < 0.05). Further, Experiment 2 showed that this difference was greater in participants who were familiar with our test beverages, indicating a role for learning. Notably, we failed to observe a significant difference in expected satiation between any of the caloric beverages and snack foods in Experiment 2 (range: 192.5-205.2 kcal; p = 0.87). This finding suggests that it may be more appropriate to consider beverages and solid foods on the same continuum, recognizing that the expected satiation of some solid foods is as weak as some beverages.

Are You Sure? Confidence about the Satiating Capacity of a Food Affects Subsequent Food Intake

Expectations about a food’s satiating capacity predict self-selected portion size, food intake and food choice. However, two individuals might have a similar expectation, but one might be extremely confident while the other might be guessing. It is unclear whether confidence about an expectation affects adjustments in energy intake at a subsequent meal. In a randomized cross-over design, 24 subjects participated in three separate breakfast sessions, and were served a low-energy-dense preload (53 kcal/100 g), a high-energy-dense preload (94 kcal/100 g), or no preload. Subjects received ambiguous information about the preload’s satiating capacity and rated how confident they were about their expected satiation before consuming the preload in its entirety. They were served an ad libitum test meal 30 min later. Confidence ratings were negatively associated with energy compensation after consuming the high-energy-dense preload (r = −0.61; p = 0.001). The same relationship was evident after consuming the low-energy-dense preload, but only after controlling for dietary restraint, hunger prior to, and liking of the test meal (p = 0.03). Our results suggest that confidence modifies short-term controls of food intake by affecting energy compensation. These results merit consideration because imprecise caloric compensation has been identified as a potential risk factor for a positive energy balance and weight gain.

So Many Brands and Varieties to Choose from: Does This Compromise the Control of Food Intake in Humans?

The recent rise in obesity is widely attributed to changes in the dietary environment (e.g., increased availability of energy-dense foods and larger portion sizes). However, a critical feature of our "obesogenic environment" may have been overlooked - the dramatic increase in "dietary variability" (the tendency for specific mass-produced foods to be available in numerous varieties that differ in energy content). In this study we tested the hypothesis that dietary variability compromises the control of food intake in humans. Specifically, we examined the effects of dietary variability in pepperoni pizza on two key outcome variables; i) compensation for calories in pepperoni pizza and ii) expectations about the satiating properties of pepperoni pizza (expected satiation). We reasoned that dietary variability might generate uncertainty about the postingestive effects of a food. An internet-based questionnaire was completed by 199 adults. This revealed substantial variation in exposure to different varieties of pepperoni pizza. In a follow-up study (n= 66; 65% female), high pizza variability was associated with i) poorer compensation for calories in pepperoni pizza and ii) lower expected satiation for pepperoni pizza. Furthermore, the effect of uncertainty on caloric compensation was moderated by individual differences in decision making (loss aversion). For the first time, these findings highlight a process by which dietary variability may compromise food-intake control in humans. This is important because it exposes a new feature of Western diets (processed foods in particular) that might contribute to overeating and obesity.

Expected Satiety: Application to Weight Management and Understanding Energy Selection in Humans

Recent advances in the approaches used to quantify expectations of satiation and satiety have led to a better understanding of how humans select and consume food, and the associated links to energy intake regulation. When compared calorie for calorie some foods are expected to deliver several times more satiety than others, and multiple studies have demonstrated that people are able to discriminate between similar foods reliably and with considerable sensitivity. These findings have implications for the control of meal size and the design of foods that can be used to lower the energy density of diets. These methods and findings are discussed in terms of their implications for weight management. The current paper also highlights why expected satiety may also play an important role beyond energy selection, in moderating appetite sensations after a meal has been consumed, through memory for recent eating and the selection of foods across future meals.

Effects of meal variety on expected satiation: evidence for a 'perceived volume' heuristic

Meal variety has been shown to increase energy intake in humans by an average of 29%. Historically, research exploring the mechanism underlying this effect has focused on physiological and psychological processes that terminate a meal (e.g., sensory-specific satiety). We sought to explore whether meal variety stimulates intake by influencing pre-meal planning. We know that individuals use prior experience with a food to estimate the extent to which it will deliver fullness. These 'expected satiation' judgments may be straightforward when only one meal component needs to be considered, but it remains unclear how prospective satiation is estimated when a meal comprises multiple items. We hypothesised that people simplify the task by using a heuristic, or 'cognitive shortcut.' Specifically, as within-meal variety increases, expected satiation tends to be based on the perceived volume of food(s) rather than on prior experience. In each trial, participants (N = 68) were shown a plate of food with six buffet food items. Across trials the number of different foods varied in the range one to six. In separate tasks, the participants provided an estimate of their combined expected satiation and volume. When meal variety was high, judgments of perceived volume and expected satiation 'converged.' This is consistent with a common underlying response strategy. By contrast, the low variety meals produced dissociable responses, suggesting that judgments of expected satiation were not governed solely by perceived volume. This evidence for a 'volume heuristic' was especially clear in people who were less familiar with the meal items. Together, these results are important because they expose a novel process by which meal variety might increase food intake in humans.

Acute sleep deprivation increases portion size and affects food choice in young men

Acute sleep loss increases food intake in adults. However, little is known about the influence of acute sleep loss on portion size choice, and whether this depends on both hunger state and the type of food (snack or meal item) offered to an individual. The aim of the current study was to compare portion size choice after a night of sleep and a period of nocturnal wakefulness (a condition experienced by night-shift workers, e.g. physicians and nurses). Sixteen men (age: 23 ± 0.9 years, BMI: 23.6 ± 0.6 kg/m(2)) participated in a randomized within-subject design with two conditions, 8-h of sleep and total sleep deprivation (TSD). In the morning following sleep interventions, portion size, comprising meal and snack items, was measured using a computer-based task, in both fasted and sated state. In addition, hunger as well as plasma levels of ghrelin were measured. In the morning after TSD, subjects had increased plasma ghrelin levels (13%, p=0.04), and chose larger portions (14%, p=0.02), irrespective of the type of food, as compared to the sleep condition. Self-reported hunger was also enhanced (p<0.01). Following breakfast, sleep-deprived subjects chose larger portions of snacks (16%, p=0.02), whereas the selection of meal items did not differ between the sleep interventions (6%, p=0.13). Our results suggest that overeating in the morning after sleep loss is driven by both homeostatic and hedonic factors. Further, they show that portion size choice after sleep loss depend on both an individual's hunger status, and the type of food offered.

Episodic memory and appetite regulation in humans

Psychological and neurobiological evidence implicates hippocampal-dependent memory processes in the control of hunger and food intake. In humans, these have been revealed in the hyperphagia that is associated with amnesia. However, it remains unclear whether ‘memory for recent eating’ plays a significant role in neurologically intact humans. In this study we isolated the extent to which memory for a recently consumed meal influences hunger and fullness over a three-hour period. Before lunch, half of our volunteers were shown 300 ml of soup and half were shown 500 ml. Orthogonal to this, half consumed 300 ml and half consumed 500 ml. This process yielded four separate groups (25 volunteers in each). Independent manipulation of the ‘actual’ and ‘perceived’ soup portion was achieved using a computer-controlled peristaltic pump. This was designed to either refill or draw soup from a soup bowl in a covert manner. Immediately after lunch, self-reported hunger was influenced by the actual and not the perceived amount of soup consumed. However, two and three hours after meal termination this pattern was reversed - hunger was predicted by the perceived amount and not the actual amount. Participants who thought they had consumed the larger 500-ml portion reported significantly less hunger. This was also associated with an increase in the ‘expected satiation’ of the soup 24-hours later. For the first time, this manipulation exposes the independent and important contribution of memory processes to satiety. Opportunities exist to capitalise on this finding to reduce energy intake in humans.