SUstainable PREvention of cardioMEtabolic risk through NUDGing hEalth behaviors

In the Supreme Nudge project, we will study the effects of pricing and nudging strategies in the supermarket – one of the most important point-of-choice settings for food choices – and of a context-specific mobile physical activity promotion app.

The Supreme Nudge trial includes nudging and pricing strategies cluster-randomised on the supermarket level, with: i) control group receiving no intervention; ii) intervention group receiving healthy food nudges (e.g., product placement or promotion) and pricing strategies (taxing of unhealthy foods and subsidizing healthy foods). In collaboration with a Dutch supermarket chain we selected eight stores located in low SEP neighbourhoods.

Across the clusters, a personalized mobile coaching app targeting moderate physical activity (walking behaviour) will be individually-randomised, with: i) control group receiving no intervention; ii) a group receiving the mobile PA app intervention.

The primary outcome is the mean individual change in adherence to the Dutch Dietary Guidelines. Secondary outcomes include cardiometabolic outcomes, and the number of steps per day, healthy food purchasing in the supermarket, food decision styles, social cognitive factors in relation to nudges and in relation to walking behaviours, supermarket customer satisfaction, at 3, and 6 (and 12; depending on participant enrolment date) months and technology acceptance and acceptance of nudges at 6 and 12 months.

The trial is reflexively monitored to support current and future implementation. The findings can guide future research and public health policies on reducing lifestyle related health inequalities and contribute to a supermarket-based health interventions implementation roadmap.

Changing the context in which individuals make lifestyle choices has a sustained impact on the dietary intake and cardiometabolic health.

The intervention phase will be 6 or 12 consecutive months (depending on participant enrolment date) to account for seasonal variation in shopping and physical activity behaviour and allow measurement of long-term effects. The short-term (3 months) measurements will be used to measure changes in behaviours and intermediate psychological constructs, whereas the longer term follow up (6 and 12 months) will be used to evaluate changes in dietary intake, and for the process-evaluation.

This cluster-randomised controlled trial will implement nudging and pricing strategies on the supermarket level, using two trial arms:

- control group receiving no intervention;

- intervention group receiving healthy food nudges and pricing strategies.

An mHealth PA coaching app will be implemented and randomised at the individual level across all supermarket level clusters to prevent clustering of mHealth participants within store locations:

- control group receiving a step count app for tracking of step count data;

- an intervention group receiving the step count app plus the PA coaching app.