A recent study by Stuber et al. in BMC Medicine reports that in-supermarket nudges and price interventions combined with personalized mobile physical activity coaching improve lifestyle behaviors and cardiometabolic health. has been done. [6] The Supreme Nudge study is a parallel cluster randomized controlled trial of 12 supermarkets located in low socio-demographic areas across the Netherlands. Supermarkets were randomly assigned to either operate as usual (control) or implement a series of co-designed interventions to promote healthier purchasing. A sample of 361 people within these supermarkets were then randomized to receive physical activity instruction via the mobile His app or a simpler pedometer app. Participants were followed for up to 12 months to see if there were improvements in diet quality, food purchasing behavior, physical activity, and cardiometabolic risk factors. However, the authors reported that none of these results changed significantly compared to the control group at the end of the study.
The Supreme Nudge study is an example of a carefully designed, complex intervention that targets individuals to increase their motivation to increase physical activity, as well as environments that promote healthier food choices. However, the lack of efficacy across all outcomes is worth considering to understand why. Supermarket interventions primarily focused on nudging strategies targeting healthier foods, including shelf position, stock availability, and signage, which account for approximately 9% of all products sold in supermarkets. The pricing strategy consisted of price reductions for healthier products and price increases for less healthy products, and was rolled out within each food category over a short period of time, targeting approximately 3% of all products. As with other low-risk supermarket-led interventions that reach a compromise between effectiveness, sustainability, and feasibility, the impact is too small to be detected. However, there are examples where interventions designed in collaboration with supermarkets have provided evidence that shopping behavior has improved without negatively impacting the business. Successful interventions were particularly dependent on limiting price promotions, positioning, and availability across the full range of discretionary foods and beverages. [7, 8]rather than focusing primarily or exclusively on encouraging healthier choices through a single mode of intervention.
One key difference between the Supreme Nudge study and other studies is that it used a measure of an individual's dietary intake as the primary outcome over a period of up to 12 months. Much of the evidence reports short-term effects on sales of the target product without considering how other products outside the target category are marketed or any compensatory effects. Therefore, changes in sales or purchasing behavior do not necessarily lead to individual changes of sufficient magnitude to improve diet quality in the long term. Stuber et al. found no significant changes in dietary intake or grocery shopping behavior, but the use of food frequency questionnaires, which are prone to reporting bias and have low sensitivity for detecting changes over time, may have influenced the results. This may have been one of the reasons why they were not obtained. Finally, the Supreme Nudge trial was conducted during the coronavirus disease (COVID-19) pandemic, which reflected significant changes to initial protocols and, due to the restrictions imposed. It may have particularly influenced typical customer behavior.
