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

Lead Research Organisation: University of Bristol
Department Name: Experimental Psychology

Abstract

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. In the 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.

Technical Summary

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.

Publications

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Brunstrom J (2010) Expected satiety influences actual satiety in Appetite

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Brunstrom JM (2012) Episodic memory and appetite regulation in humans. in PloS one

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Brunstrom JM (2009) Popular Journal in Nutrition in Practice

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Hinton E (2011) 'Anticipatory' sensory specific satiety in Appetite

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Rogers PJ (2016) Appetite and energy balancing. in Physiology & behavior

 
Description Researchers with an interest in energy intake tend to focus on 'amount eaten' or self-reported hunger and fullness after a test food has been consumed. The logic here is that meal size is normally determined by psychological and physiological 'events' during and towards the end of a meal. This project challenged this fundamental assumption and showed how an understanding of portion-size decisions can help us to identify palatable foods that promote lower energy intake.
A key objective was to develop a new methodology that can be used to provide insight into consumer expectations associated with food. During the project we developed a 'Consumer Expectations Toolbox.' This comprises a range of software that can be used to quantify various expectations, including 'expected satiety,' 'expected satiation,' food liking, food reward, memory for food, and maximum and ideal portion sizes. This software represents the implementation of techniques that were developed and validated as part of this project. Together, they enable researchers to characterise and quantify beliefs about a food or product. This approach is very novel. Nevertheless, its value has been recognised by several large national and multinational food companies who have adopted this methodology in their portfolio of industry-based research tools. It is also used widely by academic researchers, both nationally and internationally.
A second objective was to explore variables that increase 'expected satiety' (and related measures) and, critically, whether this form of learning can be sustained over time. In two large studies we used the toolbox to explore the effects of a single exposure to a novel test food. Responses to high and low energy-dense versions were influenced by i) 'eating to fullness' and ii) attention to associated visceral cues. Importantly, this pattern of results was observed and at a follow up 3-4 month later.
We also found that dieters and non-dieters responded in different ways. This is consistent with previous observations of dietary learning in these groups. Together, these findings reveal how complex beliefs change over time and they illustrate how our approach might be applied to study the dynamic nature of beliefs about a product in a commercial setting.
Exploitation Route Our findings and related methods have been used by several large food manufacturers to help them to develop foods that might confer benefits for weight management.
Sectors Agriculture, Food and Drink,Communities and Social Services/Policy,Healthcare,Other

 
Description A key objective of this project was to develop a new methodology that can be used to provide insight into consumer expectations associated with foods. During the project we developed a 'Consumer Expectations Toolbox.' This is a package of software that can be used to quantify a range of expectations, including 'expected satiety,' 'expected satiation,' food liking, food reward, memory for food, and maximum and ideal portion sizes. This software represents the implementation of techniques that were validated as part of this project. Together, they enable researchers to characterise and quantify beliefs about a food or product. This approach is very novel. Nevertheless, its value has been recognised by several large national and multinational food companies who have adopted this methodology in their portfolio of industry-based research tools. We have also used our research as a platform for a successful and ongoing BBSRC-LINK funded project (BB/J005622/1) that is joint funded by Nestlé. This work is exploring ways in which the expected satiety of foods might be increased by understanding the relationship between oral processing of food and its effect on satiation and satiety. More generally, It is important that the public are aware that expectations about satiety and satiation differ considerably across foods. Our work has helped to develop this awareness and this has been achieved in several public dissemination activities.
First Year Of Impact 2011
Sector Agriculture, Food and Drink
Impact Types Societal,Economic

 
Description FP7 EU consortium (Nudge-it)
Amount £567,528 (GBP)
Funding ID Grant Agreement 607310 (Nudge-it) 
Organisation European Commission 
Department Seventh Framework Programme (FP7)
Sector Public
Country European Union (EU)
Start 01/2014 
End 12/2018
 
Title Consumer Expectations Toolbox 
Description In addition to quantifying expected satiation and expected satiety, this software can be used to evaluate expected liking, food reward, memory for food, and maximum and ideal portion sizes. All of these techniques were evaluated and validated during the project. Together, they enable researchers to characterise and quantify beliefs about a specific food or product. 
Type Of Material Improvements to research infrastructure 
Year Produced 2010 
Provided To Others? Yes  
Impact This approach is very novel. Nevertheless, its value has already been recognised by several national and multinational food companies who have adopted this methodology in their portfolio of research tools. In addition, the tools have been adopted by other research labs, both nationally and internationally. 
 
Description Collaboration with Prof Jennie Fisher, Temple University, Philadelphia 
Organisation Temple University
Country United States 
Sector Academic/University 
PI Contribution Work conducted as part of our BBSRC-DRINC project has generated psychophysical tools that are being applied to understand dietary behaviour in obese children recruited in the Philadelphia area. This work is sponsored by Ajinomoto and forms the basis for a 12-month project.
Collaborator Contribution Our collaborators are responsible for participant recruitment and for day-to-day execution of the project.
Impact Data collection is nearing completion. No outcomes to report at this stage.
Start Year 2013
 
Description 'The Incredible Edible Show' - An interactive event based at a local science museum - 'Explore at-Bristol' 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Helped to develop and deliver demonstrations of psychological controls of food intake. Audience was primarily school-age children and their parents.

Feedback from the public-science exhibition staff was extremely positive. This led to a longer-term collaboration to enable further public dissemination of activities in this museum.
Year(s) Of Engagement Activity 2012
 
Description . "What is 'expected satiety' and why is it relevant to weight management?" 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Vitafoods is the yearly event for the food industry showcasing new research findings, ingredients and raw materials for the nutraceutical, functional food and drink and nutricosmetic industries.

After this talk I engaged with a wide range of companies broadly working in the nutrition/nutraceutical space.
Year(s) Of Engagement Activity 2009
 
Description BBC Radio 4 Food Programme 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Participation in radio broadcast which sparked discussion about food cravings and preferences.

Increased public awareness regarding the factors which contribute to food choice.
Year(s) Of Engagement Activity 2012
URL http://www.bbc.co.uk/programmes/p00yyr41
 
Description Campden Foods - Jan 2009. "Understanding decisions about portion size: The key to acceptable foods that reduce energy intake?" 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Briefing to industry consortium comprising UK food companies

Discussion around future funded projects.
Year(s) Of Engagement Activity 2009
 
Description Live experiment for AT-Bristol Science Centre 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact In collaboration with At-Bristol Science Centre colleagues conducted live experiment on eating behaviour, namely sensory-specific satiety for popcorn flavours. Audience/participants were adults attending 'After Hours' event. Results were updated as each participant completed their session, accompanied by live feedback and explanation of the study and the background science.
Year(s) Of Engagement Activity 2016
URL http://www.bristol.ac.uk/expsych/research/brain/nbu/news/2016/afterhours.html
 
Description Live research demonstration at Bristol Half Marathon 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact On Sunday 13th September 2015, thousands of runners took part in Bristol's 27th annual half marathon. Dani Ferriday, Duncan McCaig, and Christina Potter from the Nutrition and Behaviour Unit (NBU) were on site in Anchor Square to speak to interested members of the public about the group's research. Using an interactive demonstration, they discussed the meaning of the term 'calorie' and illustrated how our beliefs about the amount of fullness that a food will deliver ('expected satiety') are not based solely on the number of calories that a food contains but other factors as well. For example, they showed that foods that are more familiar to us and foods that are larger are expected to deliver more fullness even when they are presented in portions with an identical number of calories. There was a lot of interest from those who participated in taking part in further NBU research.
Year(s) Of Engagement Activity 2015
URL https://www.bristol.ac.uk/expsych/news/2015/266.html
 
Description Media interest (Distraction leads to overeating) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Our results were disseminated to several international news sources (e.g., NPR, NY Times) and social networking sites.

Media coverage of our research sparked discussion about the role of cognition, particularly memory processes, in the control of appetite and food intake.
Year(s) Of Engagement Activity 2010,2011,2012
URL http://www.bristol.ac.uk/news/2010/7390.html
 
Description Media interest (Expected satiety influences actual satiety) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact This press release was picked up by several news/online outlets and on social media (e.g., twitter).

This sparked greater understanding/discussion about the role of expectations in appetite control.
Year(s) Of Engagement Activity 2010
URL http://www.bristol.ac.uk/news/2010/7105.html
 
Description Media interest (Memory influences appetite) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Results were disseminated to a variety of international news sources (e.g., NPR) and social networking sites.

Media coverage of our findings sparked discussion about the role of cognition, specifically memory processes, in the control of appetite and food intake.
Year(s) Of Engagement Activity 2010,2011,2012
URL http://www.bris.ac.uk/news/2010/7105.html
 
Description Media interest (Portion size, expected satiety, and the role of dietary variability) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Current research projects were highlighted on BBSRC website.

Web coverage of our projects highlighted our current lines of research, attracting new interest in our research team.
Year(s) Of Engagement Activity 2013
URL http://www.bbsrc.ac.uk/news/health/2013/130204-f-would-you-like-to-supersize-that.aspx
 
Description Stall at Food Matters Live 2016 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact More than 13,500 experts from across the food, health and nutrition sectors attended Food Matters Live 2016. The Nutrition and Behaviour Unit hosted a stall at this event and featured a Powerpoint projection which detailed current research projects/ideas, methodologies, facilities. Recent scientific publications were also available for distribution. This stall sparked interest, conversations and requests for further information.
Year(s) Of Engagement Activity 2016
URL https://www.foodmatterslive.com/