The GRoceries Aimed at Increasing Nutrition Study

The overall objective of this study is to determine if behaviorally informed marketing strategies or those same strategies plus dynamically adapted financial incentives can prompt consumers with prediabetes or diabetes to switch from refined to whole grain products when grocery shopping online. The specific aims of the study are:

Aim 1: To demonstrate the feasibility of conducting a randomized controlled trial (RCT) via an online grocery delivery platform and to refine mechanism-based marketing nudges and incentives based on user insights. The overall objective of this aim is to customize the online grocery store experience to align with the needs of the consumers while also supporting the objectives of the two intervention arms outlined in Aim 2. Customizations will include displaying whole grains (e.g., whole wheat bread, brown rice) at the top of the study's online grocery store, featuring whole grain banner displays, and offering product swaps to highlight whole grain alternatives. Additionally, the study team will ensure that all refined grain items have corresponding whole grain options, to the extent possible. To evaluate the platform's usability and gather insights for refining the interventions, the study team will recruit 9 participants to test the customized online grocery store. Participants will provide feedback on the online shopping environment and whole grain options in an end-of-study survey. This feedback will be used to refine the marketing nudge interventions for Aim 2.

Aim 2: To test whether behaviorally informed marketing strategies or those same strategies plus dynamically adapted financial incentives can prompt consumers with prediabetes or diabetes to switch from buying refined grain products to whole grain products when grocery shopping online. Enrolled participants will be randomized to one of three intervention arms: 1) control (no intervention), 2) marketing nudges, or 3) marketing nudges + dynamically adapted financial incentives. Participants will select groceries from the study's online grocery store, and the orders will be delivered to their homes via a third-party delivery service. The first two weeks will serve as a baseline period for data collection. Starting in Week 3, participants in intervention arms 2 and 3 will be exposed to marketing nudges promoting whole grains for 8 weeks. Participants in the third intervention arm will additionally receive personalized financial incentives with individual incentive amounts optimized weekly based on prior whole grain purchasing behavior and engagement. In a typical healthy eating incentive study, all participants would get the same incentive amount each week. An innovative aspect of this study is to dynamically adapt the incentive, so each person experiences a personalized offering of incentives each week based on their whole grain shopping habits in prior weeks. This means participants who did not buy a whole grain item in response to a smaller incentive in a prior week may receive a larger incentive than participants who did purchase whole grains when offered the smaller incentive. This will not be gameable since it will not be apparent to participants a priori. This approach enables us to mimic current retailer practices, rather than more outdated strategies that provide the same incentive weekly.

Aim 3: To examine whether whole grain purchasing behaviors have become habitual and persist after the marketing nudges and dynamically adapted financial incentives cease. The overall objective of this aim is to explore the potential for marketing strategies and dynamically adapted financial incentives to create lasting changes in grocery shopping habits, specifically by examining whether participants continue purchasing whole grain products once the intervention has ended. Participants will be followed for an additional 8 weeks post-intervention to track their online grocery shopping behavior in the absence of the marketing nudges and financial incentives. During this period, participants will continue to shop through the study's online grocery store and have their groceries delivered to them through a third-party delivery service. In addition, for the first 4 weeks of follow-up, they will continue to receive their weekly $10 incentive if they shop in the study's online grocery store. At the conclusion of the study, participants will receive a $25 incentive for completing a survey assessing the intervention's salience, their acceptance of whole grains, and any remaining barriers to switching to whole grains.

• Change in calories purchased from products that are majority refined grains over time [Time frame: 18 weeks]
• Percent of cart spent on whole grains (total dollar on whole grains/cart total) [Time frame: 18 weeks]
• Change in dollars spent on products that are majority whole grains over time [Time frame: 18 weeks]
• Assessing whole and refined grain purchasing frequency [Time frame: Assessed at baseline and in end-of-study survey (Week 18)]
• Percentage of time grains were purchased as whole and refined grains [Time frame: Assessed at baseline and in end-of-study survey (Week 18)]
• Assessing whole and refined grain consumption frequency [Time frame: Assessed at baseline and in end-of-study survey (Week 18)]
• Percentage of time grains were consumed as whole and refined grains [Time frame: Assessed at baseline and in end-of-study survey (Week 18)]
• Amount of grains eaten at a time [Time frame: Assessed at baseline and in end-of-study survey (Week 18)]
• Perception of whole grains: satisfaction with current whole grain consumption [Time frame: Assessed at baseline and in end-of-study survey (Week 18)]
• Perception of whole grains: beliefs about the impact of eating whole grains on health [Time frame: Assessed at baseline and in end-of-study survey (Week 18)]
• Perception of whole grains: enjoyment of eating whole grains [Time frame: Assessed at baseline and in end-of-study survey (Week 18)]
• Perception of whole grains: efforts to include whole grains in diet [Time frame: Assessed at baseline and in end-of-study survey (Week 18)]