This study will be a 2x2 randomised controlled trial with information-based intervention (no labelling / labelling) and structural intervention (default proportion / increased proportion of lower energy density food items) as between-subject factors and energy density (kcal/g) of food purchases during an online supermarket-shopping task as dependent variable. This study will use an online supermarket platform developed to mimic an online supermarket website and participants will be asked to complete a shopping task using a pre-determined shopping list of 10 items.
See attached protocol documents.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
NONE
Enrollment
1,000
The proportion of lower energy density vs. higher energy density items will be reversed (67% lower - 33% higher) relative to the default proportion condition (D and DL) (33% lower - 67% higher). Lower energy density items will be defined as lower energy density ≤ median of energy density distribution within a food category.
When energy density of an item ≤ median of ED distribution within a food category, "healthier choice" badges will be added to the food item pictures on the online supermarket. Instructions when logging-into the platform will introduce the badges to the participants: "In the online supermarket, the green tick allows you to see which products (e.g. muesli) in each product category (e.g. cereals) are healthier choices with fewer calories per gram than most other products in the same category."
University of Liverpool
Liverpool, Merseyside, United Kingdom
Mean ED of the food items purchased (kcal/100g)
Calculated as the sum of the energy of the purchased items (kcal) divided by the sum of their weight (g) and multiplied by 100.
Time frame: 20 minutes (the time frame denotes time taken to make the food shopping task online and there is no follow up)
Total energy of the food items purchased (kcal)
Calculated as the sum of the energy of the purchased items (kcal)
Time frame: 20 minutes (the time frame denotes time taken to make the food shopping task online and there is no follow up)
Energy from total sugar (% of total energy)
Calculated as the percentage of total energy of the purchased items from total sugar
Time frame: 20 minutes (the time frame denotes time taken to make the food shopping task online and there is no follow up)
Energy from saturated fatty acids (SFA) (% of total energy)
Calculated as the percentage of total energy of the purchased items from SFA
Time frame: 20 minutes (the time frame denotes time taken to make the food shopping task online and there is no follow up)
Salt content (g/100g)
Calculated as the sum of the salt content of the purchased items (g) divided by the sum of their weight (g) and multiplied by 100.
Time frame: 20 minutes (the time frame denotes time taken to make the food shopping task online and there is no follow up)
Proportion of lower energy density food items in the basket of foods purchased
Lower energy density items will be defined as ≤ median of energy density distribution within a food category
Time frame: 20 minutes (the time frame denotes time taken to make the food shopping task online and there is no follow up)
Cost (GPB)
Calculated as the sum of the prices of the purchased items
Time frame: 20 minutes (the time frame denotes time taken to make the food shopping task online and there is no follow up)
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