The study, funded by the National Institute for Health Research, was published in the open access International Journal of Behavioural Nutrition and Physical Activity.
The study's lead author, Dr Dimitrios Koutoukidis, a researcher in the Nuffield Department of Primary Care Health Sciences, said: “Finding effective ways of lowering the saturated fat in our shopping baskets, such as from meat, cheese, or desserts, may translate to eating less of it, which could help lower our risk for heart disease. This is the first randomised trial to directly compare interventions targeting the environment and the individual to encourage healthier food choices. The findings could provide effective strategies to improve the nutritional quality of online food purchases.”
Dr Koutoukidis and colleagues conducted an experiment with 1088 grocery shoppers from UK households, using an experimental online supermarket specifically designed for the study.
Participants were asked to select ten ‘everyday’ foods that they and their household would want to eat, from a pre-specified shopping list.
Participants were randomly allocated to one of four groups. The first group was shown a list of food products ranked according to their saturated fat content from low to high (environmental-level intervention). The second group was offered the option to swap a product high in saturated fat for a similar one with lower saturated fat (individual-level intervention). The third group was shown a combination of both the ranked list and offered the option to swap products (combined intervention), while the fourth group was shown neither a ranked list, nor given the option to swap products (no intervention control).
These results could be capitalised by online supermarkets which could implement either or both strategies knowing that they are potentially effective for lowering the saturated fat in their customers’ shopping baskets and thus shape healthier food choices.
Dr Dimitrios Koutoukidis
The authors found that participants in any of the intervention groups chose products with less saturated fat than those who received no intervention. Altering the default order was more effective than offering product swaps. Combining the two was more effective than offering swaps but no more effective than altering the default order of items.
For participants who received no intervention, the percentage of calories from saturated fat in their shopping baskets was 25.7%. Altering the order of foods or offering swaps reduced the percentage calories from saturated fat by 5.0% and 2.0%, respectively. A combination of both interventions reduced it by 5.4% compared to controls. The total cost of the shopping basket did not differ significantly between groups.
The authors caution that these interventions need to be tested now in real online supermarkets, as this was an experimental platform where participants chose but did not receive the food and did not spend their own money. As the pre-specified shopping list focused on foods high in saturated fat, the effect of these interventions would likely be smaller during real-life shopping which would include a broader range of products.
Prominent positioning and food swaps are effective interventions to reduce the saturated fat content of the shopping basket in an experimental online supermarket: a randomized controlled trial
Koutoukidis et al. International Journal of Behavioral Nutrition and Physical Activity 2019