Optimizing an mHealth Intervention to Change Food Purchasing Behaviors for Cancer Prevention

"If participants are randomized to have this component ON, the app will send the notification when the participant's smartphone is within a 50-meter geofence around designated grocery stores. No more than one notification will be sent per week. Mindfulness of program goals in the moment of decision making is expected to facilitate program-consistent food purchasing behaviors. Participants assigned to have location-triggered message delivery OFF will receive their weekly recommendations and reminders messages at standard times throughout the week. The content of the messages will not differ according to whether this component is ON vs. OFF."

Participants will reflect on anticipated benefits of purchasing healthy foods, consistent with motivational interviewing and self-determination theory. Message content will be personalized as follows: During the initial workshop, all participants will complete an exercise identifying benefits of healthy eating that are important to them. Message content will then be programmed to be personalized according to anticipated rewards important to that participant. Participants assigned to have this intervention component OFF will not have content about anticipated benefits of change added to any messages.

Coaches will monitor participant food purchases via a dashboard for viewing purchase data, and send messages designed to provide feedback and enhance supportive accountability for program goals. The messages will provide reinforcement for purchases consistent with program goals and express concern for areas in which adherence is low. Participants assigned to have this component OFF will not receive these extra messages or phone calls, and their food purchases will only be viewed by research staff for research outcome assessment purposes.

If participants are assigned to have household support ON, one adult in the household will receive weekly text messages designed to elicit support for changing food purchases. In addition, the index participant and household member will be invited to participate in one extra workshop session and three brief coaching calls focused on household support. If participants are assigned to have this OFF, household members will have no program involvement.