Plain English Summary
Background and study aims
Poor diet is a risk factor for heart disease. Saturated fat (SFA) in food increases the type of cholesterol (LDL-cholesterol) that increases the chances of heart disease. Cutting down on food containing SFA, e.g. swapping butter for plant-based spreads, could help lower the risk of heart disease. Researchers are currently investigating new ways of reducing SFA in the population's diet. This study is an online shopping experiment to find out which are the best food swaps which achieve the greatest impact on SFA, and also the swaps which are most acceptable to people. The researchers are also interested in whether they can change purchases by changing the way foods choices are presented online.
Who can participate?
Healthy volunteers aged 18 and over
What does the study involve?
Participants do a 'pretend' shop in an online supermarket specially designed to conduct this kind of experiment. They are randomly allocated to one of for groups. One group is offered lower SFA swaps to the products they first select. In a second group the position of foods in the list which appears on screen is changed so that lower SFA options are positioned higher up. In the third group both of these interventions are applied together. The fourth group see the default version of the website with no swaps offered and a random order of the foods displayed in response to each search. The amount of SFA in the final basket is calculated for the four groups.
What are the possible benefits and risks of participating?
If successful, these strategies can be delivered at scale supporting current efforts to help people make lifestyle changes to lower their risk of chronic diseases. There are no direct benefits or risks involved in participating in this study, but the participants are reimbursed for their effort.
Where is the study run from?
University of Oxford (UK)
When is the study starting and how long is it expected to run for?
February 2018 to February 2019
Who is funding the study?
National Institute for Health Research (NIHR) (UK)
Who is the main contact?
Dr Dimitrios Koutoukidis
The effectiveness of individual-level and environmental-level interventions on food choices: an experimental online supermarket study
To investigate the magnitude of saturated fat change achieved in the shopping basket in response to an individual-level intervention and an environmental-level intervention, separately and in combination, compared to control (no intervention).
University of Oxford, Medical Sciences Interdivisional Research Ethics Committee, 08/02/2018, ref: R55722/RE001
Randomised controlled trial with a 2x2 factorial design
Primary study design
Secondary study design
Randomised controlled trial
Patient information sheet
Not available in web format, please use the contact details to request a patient information sheet
This study uses a bespoke virtual online supermarket shopping (OLS) platform, hosted by The University of Oxford, which emulates a real online supermarket for research purposes relating to food purchasing interventions. Participants will be randomly allocated to one of the following groups when shopping online:
1. Individual-level intervention: offering a swap to a product with less saturated fat (SFA)
Swaps will be offered at point of selection i.e. when a participant selects an item to put in their shopping basket, if an alternative product exists that is lower in SFA within the same food category, the participant will be offered the chance to swap the item. Products offered as swaps will be within the same general price and weight range as the original item.
2. Environmental-level intervention: prominent positioning of lower SFA options
This will apply to each list of foods offered to participants when searching for products.
3. A combination of individual- and environmental-level interventions
This group will receive both interventions as described above.
Participants in this group will see the default version of the website with no swaps offered and a random order of the foods displayed in response to each search.
Primary outcome measure
Current primary outcome measure as of 20/07/2018:
The difference in the saturated fat content of the final basket (measured in % of total energy) between each of the four trial arms
Previous primary outcome measure:
Difference in the saturated fat change of the final basket (measured in % of total energy) between each single intervention group and control; between combined intervention groups and each single intervention group; and between combined intervention groups and control
Secondary outcome measures
Current secondary outcome measures as of 20/07/2018:
The following outcomes will be compared between each of the four trial arms:
1. Difference in the proportion of products with lower saturated fat in the final basket (%)
2. Difference in the overall cost of the final shopping basket (£) weighted for the size of the basket (g)
3. Difference in the total energy, energy density, sugars (% energy), and salt (g/100g) content of the shopping basket
The following outcomes will be compared between the single individual-level intervention (swaps only) and the combined intervention arms:
4. Difference in % saturated fat content per swap accepted (% energy intake)
5. Difference in the proportion of swaps accepted out of those offered (%)
6. Difference in the proportion of swaps accepted out of those offered (%) by median observed change in saturated fat
7. Difference in the proportion of swaps accepted out of those offered (%) for (a) butter, margarine, and spreads, (b) cheese, (c) milk, (d) meat, and (e) sweets and desserts
8. Difference in the proportion of accepted swaps out of total shopping basket items (%)
Previous secondary outcome measures:
Difference between intervention vs control:
1. The proportion of products with lower saturated fat in the final basket (%)
2. % saturated fat content per swap accepted (% energy intake)
3. The proportion of swaps accepted out of those offered (%)
4. The proportion of accepted swaps out of total shopping basket items (%)
5. The overall cost of the final shopping basket (£) weighted for the size of the basket
6. The total energy, energy density, sugars (% energy) and salt (g/100g) content of the shopping basket
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1. UK adults, aged ≥18 years
2. Able to speak and read English
3. Willing and able to give informed consent for participation in the study
4. Being the main (or shared) grocery shopper for their household
5. Having access to a computer and Internet
Target number of participants
Participant exclusion criteria
Having any dietary restriction
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
University of Oxford
Radcliffe Observatory Quarter Woodstock Road
National Institute for Health Research
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
The study protocol will become available. The statistical analysis plan created prior to running the statistical analysis is available. Planned publication of the study results in a high-impact peer reviewed journal.
IPD sharing statement
The current data sharing plans for the study are unknown and will be made available at a later date.
Intention to publish date
Participant level data
To be made available at a later date
Basic results (scientific)
- ISRCTN13729526_SAP_v1.0_13Jul18.pdf Uploaded 20/07/2018