Award details

Understanding decisions about portion size: The key to acceptable foods that reduce energy intake?

Reference	BB/G005443/1
Principal Investigator / Supervisor	Professor Jeffrey Brunstrom
Co-Investigators / Co-Supervisors	Professor Peter Rogers
Institution	University of Bristol
Department	Experimental Psychology
Funding type	Research
Value (£)	376,251
Status	Completed
Type	Research Grant
Start date	01/03/2009
End date	31/08/2012
Duration	42 months

Abstract

People have very clear expectations about the satiety that will develop after consuming particular foods. Nevertheless, our findings show that a considerable mismatch exists between expected satiety and actual energy content (e.g. 200 kcal of pasta and 894 kcal of cashews are expected to deliver equal satiety). This observation is critical, because foods that have high-expected satiety are likely to promote reduced energy intake. In Phase 1 we will formally investigate the importance of portion-size decisions. We will draw upon a range of measures, including cutting edge 'e-diary' technology that enables participants to report their hunger and satiety and record images of food portions using mobile phones that are loaded with bespoke software. In Phase 2 we will quantify food expectations using a psychophysical tool (developed at Bristol) that uses an adapted method of constant stimuli. By assessing a wide range of foods we will identify particular food characteristics that promote high levels of expected satiation/satiety. We will focus on nutrient composition and other attributes, including perceived amount/volume, beliefs about energy content, perceived health benefits, and product labelling. We will also explore the relative importance of the affective (hedonic) qualities of test foods and how they combine in the mind of the assessor when making decisions about portion size. In so doing, our aim is to propose particular foods that will help to reduce energy intake, and to deliver a rigorous methodology for exploring other foods and food characteristics in future. In Phase 3 we will explore how decisions about ideal portion-size change after repeated exposure to an otherwise identical high- or low-energy dense food. In so doing we aim to explain changes that can occur in the acceptability 'diet foods' as they become more familiar. In a second study we will explore whether product information or food familiarity can militate against this relearning.

Summary

Researchers have long been interested in the prospect of developing enjoyable foods that are filling yet low in calories. In almost all studies the critical dependent measure has been 'amount eaten' or some other assessment of feelings of hunger and fullness after a particular test food has been consumed. The logic here is that the amount eaten is normally determined by psychological and physiological effects of eating that take place during and towards the end of a meal. This project will 1) challenge this fundamental assumption and 2) show how an understanding of portion-size decisions can help us to identify palatable foods that promote lower energy intake. The first phase of this project will seek evidence that on occasions when we have control over meal size (which we suspect is very often), the most important determinant of food intake is the decision-making that underlies how much is chosen before a meal begins. In so doing, we aim to provide 1) evidence that 'traditional' methods are not best placed to develop foods that reduce energy intake, and 2) a justification for a new approach for asking questions about food characteristics and their effect on decisions about portion size. After establishing the importance of portion-size decisions, phase two will explore the basis on which decisions about portion-sizes are made. Particular emphasis will be placed on modelling the relative importance of liking for the test foods and expectations about how filling they are, focusing on how these factors combine in the mind of a consumer. In so doing, we will be able to propose particular foods that may help to reduce energy intake, and we will deliver new methods that can be used to explore many other foods in future. Finally, it is important to say that we are not proposing that physiological effects of eating play little or no role in influencing energy intake, merely that their role is secondary to portion-size decisions during individual meals. Inthe longer term, physiological feedback of this kind could be very important. Indeed, we suspect that portion-size decisions are, in part, learned from previous experiences of the filling effects of different foods. The final phase (phase 3) of this project will test this proposition. This research will inform our understanding of the origin of portion-size decisions. This may explain changes that can occur in the acceptability and use of low-energy 'diet foods' after they become familiar to a consumer, and it will highlight ways of 'protecting' against a decrease in acceptability over time.

Committee	Closed Committee - Agri-food (AF)
Research Topics	Diet and Health, Neuroscience and Behaviour
Research Priority	X – Research Priority information not available
Research Initiative	Diet and Health Research Industry Club (DRINC) [2008-2014]
Funding Scheme	X – not Funded via a specific Funding Scheme

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