Plain English Summary
Background and study aims
Prompting people with healthier alternative foods is a simple way to shift people towards buying healthier food, and has been used in a number of healthy eating campaigns. Recent work has explored the impact of offering automatically-selected lower-calorie swaps on an experimental supermarket website. This study found no overall effects of swaps, due to participants often not accepting the swaps or accepting swaps with a smaller reduction in calories. Those people who accepted more swaps did show reductions in the calories of their purchases. The current study aims to extend this work by testing whether framing the swap without appealing to health, instead using cost or social norms, might improve swap acceptance, and the impact of combining two of these frames.
Who can participate?
People aged 18-80 who are responsible for “about half” or “all or most” of the food/grocery shopping.
What does the study involve?
All participants are asked to shop for 10 items in an online supermarket shopping situation using an experimental website. At the end of the shopping task participants are presented with swaps offering healthier food choices, which are also cheaper than the initially selected item. Participants are randomly allocated to one of three groups, with each group using one of the following three phrases to offer the swaps:
1. “Swap to save calories”
2. “Swap to save money”
3. “Swap to this product chosen by customers who buy similar groceries to you”
What are the possible benefits and risks of participating?
Participants are unlikely to gain or lose anything from participating in the study.
Where is the study run from?
Behaviour and Health Research Unit, Cambridge University (UK).
When is study starting and how long is it expected to run for?
The study will run for 1 week in October 2015.
Who is funding the study?
Public Health England (UK).
Who is the main contact?
Message framing for uptake of within-category healthy food swaps: an experimental online supermarket study across socio-economic groups
1. Swaps framed in terms of the cost benefit or social norms are more likely to be accepted than swaps framed in terms of health benefit
2. Swaps framed in terms of cost are more accepted by individuals in low socioeconomic status (SES) groups whereas swaps framed in terms of health are more accepted by those in high SES groups
Cambridge Psychology Research ethics committee, 03/09/2015, PRE 2015 056
Three-arm randomised controlled trial
Primary study design
Secondary study design
Randomised controlled trial
Patient information sheet
Online supermarket shopping
The study will follow a between-subjects experimental design with three arms, assessing the impact of swap framing on swap acceptance. The effects will be compared with a simple health framing control. All participants are randomly allocated to one of three conditions. Groups will differ in the wording used at the top of the swap window.
1. Swap framed in terms of health alone (control): “Swap to save calories”
2. Swap framed in terms of cost alone: “Swap to save money”
3. Swap framed in terms of social norm alone: “Swap to this product chosen by customers who buy similar groceries to you”
Primary outcome measure
Proportion accepted swaps: number of swaps accepted, number of swaps offered
Secondary outcome measures
1. Energy density (kJ per 100g) of the basket of goods purchased and the basket of original goods chosen, i.e. had swaps not been offered
2. Nutrient content of basket of goods purchased and of basket of original goods chosen including saturated fat, total sugar and salt
3. Acceptability of intervention – measured after completion of shopping.
6. Self-reported weight
7. Self–reported height
8. SES: individual level – both highest educational qualification (UK census levels) and household income
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
Participants will be recruited via a research agency and will cover a spread of socio-economic status ABC1 (53%), C2DE (47%), gender (50:50) and age (18 to 80). Screening questions will be used to ensure all participants are responsible for “about half” or “all or most” of the food/grocery shopping (UK national surveys indicate this to be the case for 73% of the population (Food Standards Agency, 2011)).
Target number of participants
Participant exclusion criteria
Participants who are not responsible for “about half” or “all or most” of the food/grocery shopping
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Public Health England
Trial participating centre
Behaviour and Health Research Unit, Cambridge University
Public Health England
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Conferences and academic journals
Intention to publish date
Participant level data
Not expected to be available
Basic results (scientific)