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

Cross-over studies underestimate energy compensation:The example of sucrose-versus sucralose-containing drinks

AbstractThe vast majority of preload-test-meal studies that have investigated the effects on energy intake of disguised nutrient or other food/drink ingredient manipulations have used a cross-over design. We argue that this design may underestimate the effect of the manipulation due to carry-over effects. To test this we conducted comparable cross-over (n = 69) and parallel-groups (n = 48) studies testing the effects of sucrose versus low-calorie sweetener (sucralose) in a drink preload on test-meal energy intake. The parallel-groups study included a baseline day in which only the test meal was consumed. Energy intake in that meal was used to control for individual differences in energy intake in the analysis of the effects of sucrose versus sucralose on energy intake on the test day. Consistent with our prediction, the effect of consuming sucrose on subsequent energy intake was greater when measured in the parallel-groups study than in the cross-over study (respectively 64% versus 36% compensation for the 162 kcal difference in energy content of the sucrose and sucralose drinks). We also included a water comparison group in the parallel-groups study (n = 24) and found that test-meal energy intake did not differ significantly between the water and sucralose conditions. Together, these results confirm that consumption of sucrose in a drink reduces subsequent energy intake, but by less than the energy content of the drink, whilst drink sweetness does not increase food energy intake. Crucially, though, the studies demonstrate that study design affects estimated energy compensation

No difference in compensation for sugar in a drink versus sugar in semi-solid and solid foods

AbstractIt is claimed that sugar consumed in a drink is poorly compensated for by a reduction in subsequent energy intake, however very little research has tested directly the effect on appetite of adding sugar to a drink versus food. In this between subjects study, 144 participants (72 men) consumed preloads sweetened with either sucrose or the low-energy sweetener, sucralose (preload energy difference 162kcal) in the form of a blackcurrant drink, jelly or candy. The different preload viscosities were achieved by varying the amount of thickener (carrageenan) and water in the recipes. Participants completed hunger ratings before and 5, 10 and 20min after consuming their preload. After the 20-minute rating they were served a test-meal comprising an excess of bite-sized sandwiches and a sweet dessert. Energy intake measured for the same meal consumed the previous day (baseline day, no preload consumed) was used in the data analyses to control for individual differences in energy intake. Overall, there was 36% compensation for the energy difference in the preloads, but this did not vary with preload viscosity — if anything compensation was greater for the drink preload, and greater in men. The drink preload also showed an effect of sucrose versus sucralose for hunger. The lack of the predicted effect of viscosity on compensation could not be explained by differences in blood-glucose concentration 20min after the preload (measured in a separate study) or by differences in preload sweetness, flavour intensity, liking or familiarity. Comparison of baseline and test-meal food intakes indicated that, irrespective of energy content, the sweet drinks reduced the relative intake of sweet food. In conclusion, short-term energy compensation did not differ across a set of realistic drink and food stimuli

Subtle changes in the flavour and texture of a drink enhance expectations of satiety

Background: The consumption of liquid calories has been implicated in the development of obesity and weight gain. Energy-containing drinks are often reported to have a weak satiety value: one explanation for this is that because of their fluid texture they are not expected to have much nutritional value. It is important to consider what features of these drinks can be manipulated to enhance their expected satiety value. Two studies investigated the perception of subtle changes in a drink’s viscosity, and the extent to which thick texture and creamy flavour contribute to the generation of satiety expectations. Participants in the first study rated the sensory characteristics of 16 fruit yogurt drinks of increasing viscosity. In study two, a new set of participants evaluated eight versions of the fruit yogurt drink, which varied in thick texture, creamy flavour and energy content, for sensory and hedonic characteristics and satiety expectations. Results: In study one, participants were able to perceive small changes in drink viscosity that were strongly related to the actual viscosity of the drinks. In study two, the thick versions of the drink were expected to be more filling and have a greater expected satiety value, independent of the drink’s actual energy content. A creamy flavour enhanced the extent to which the drink was expected to be filling, but did not affect its expected satiety. Conclusions: These results indicate that subtle manipulations of texture and creamy flavour can increase expectations that a fruit yogurt drink will be filling and suppress hunger, irrespective of the drink’s energy content. A thicker texture enhanced expectations of satiety to a greater extent than a creamier flavour, and may be one way to improve the anticipated satiating value of energy-containing beverages

When do children learn how to select a portion size?

The reduction of portion sizes supports weight-loss. This study looks at whether children have a conceptual understanding of portion size, by studying their ability to manually serve a portion size that corresponds to what they eat. In a clinical setting, discussion around portion size is subjective thus a computerised portion size tool is also trialled, with the portion sizes chosen on the screen being compared to amounts served manually. Children (n=76) age 5-6, 7-8 and 10-11 were asked to rate their hunger (VAS scale), liking (VAS scale) and ‘ideal portion size for lunch’ of eight interactive meal images using a computerised portion size tool. Children then manually self-served and consumed a portion of pasta. Plates were weighed to allow for the calculation of calories served and eaten. A positive correlation was found between manually served food portions and the amount eaten (r =.53, 95%CI [.34, .82, P<.001), indicating that many children were able to anticipate their likely food intake prior to meal onset. A regression model demonstrates that age contributes to 9.4% of the variance in portion size accuracy (t(68)= -2.3, p=.02). There was no relationship between portion size and either hunger or liking. The portion sizes chosen on the computer at lunchtime correlated to the amount manually served overall (r=.34, 95%CI [.07, .55], p<.01), but not in 5-6-year-old children. Manual portion-size selection can be observed in five-year olds and from age seven, children’s ‘virtual’ responses correlate with their manual portion selections. The application of the computerised portion-size tool requires further development but offers considerable potential

Inadequacy of protein intake in older UK adults

The current dietary recommendation for protein intake in the UK is 0.75 g/kg/day, however, this population-wide recommendation does not necessarily reflect altered requirements for older adults to maintain muscle protein synthesis, nor does it encompass the potential impact of intake timing. Optimal muscle protein synthesis in older adults requires both higher intake requirements and a distribution of protein intake above a 25 g threshold, three times across the day. This study aimed to describe the protein intake of older adults in a UK region and compare the results to recommendations. The study re-assessed two existing datasets with rich diet information for older adults in the South Yorkshire area. Data were extracted from food diaries of 256 adults aged between 65 and 89 years old (mean ± SD 72.4 ± 5.3 years). Quantity and timing of intake were coded using Nutritics software and compared to recommendations. The relationship between body mass index (BMI), age, and protein intake was explored. Fewer than 50% of the participants met current UK recommendations (0.75 g/kg/day) and fewer than 15% met the ESPEN 1.2 g/kg/day age-specific recommendation. Only one participant met the 25 g/meal recommendation across three meals. These findings suggest that the older adult population is not achieving recommendations to maintain muscle protein synthesis. Nonetheless it identifies several straightforward opportunities for improvement, notably elevation of morning intake

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

Development and validation of a new methodological platform to measure behavioral, cognitive, and physiological responses to food interventions in real time

To fully understand the causes and mechanisms involved in overeating and obesity, measures of both cognitive and physiological determinants of eating behavior need to be integrated. Effectively synchronizing behavioral measures such as meal micro-structure (e.g., eating speed), cognitive processing of sensory stimuli, and metabolic parameters, can be complex. However, this step is central to understanding the impact of food interventions on body weight. In this paper, we provide an overview of the existing gaps in eating behavior research and describe the development and validation of a new methodological platform to address some of these issues. As part of a controlled trial, 76 men and women self-served and consumed food from a buffet, using a portion-control plate with visual stimuli for appropriate amounts of main food groups, or a conventional plate, on two different days, in a random order. In both sessions participants completed behavioral and cognitive tests using a novel methodological platform that measured gaze movement (as a proxy for visual attention), eating rate and bite size, memory for portion sizes, subjective appetite and portion-size perceptions. In a sub-sample of women, hormonal secretion in response to the meal was also measured. The novel platform showed a significant improvement in meal micro-structure measures from published data (13 vs. 33% failure rate) and high comparability between an automated gaze mapping protocol vs. manual coding for eye-tracking studies involving an eating test (ICC between methods 0.85; 90% CI 0.74, 0.92). This trial was registered at Clinical Trials.gov with Identifier NCT03610776

Protein for Life: Review of Optimal Protein Intake, Sustainable Dietary Sources and the Effect on Appetite in Ageing Adults

With an ageing population, dietary approaches to promote health and independence later in life are needed. In part, this can be achieved by maintaining muscle mass and strength as people age. New evidence suggests that current dietary recommendations for protein intake may be insufficient to achieve this goal and that individuals might benefit by increasing their intake and frequency of consumption of high-quality protein. However, the environmental effects of increasing animal-protein production are a concern, and alternative, more sustainable protein sources should be considered. Protein is known to be more satiating than other macronutrients, and it is unclear whether diets high in plant proteins affect the appetite of older adults as they should be recommended for individuals at risk of malnutrition. The review considers the protein needs of an ageing population (>40 years old), sustainable protein sources, appetite-related implications of diets high in plant proteins, and related areas for future research