This study is a randomized controlled trial (RCT) which investigates the effect of a Future-Self Avatar intervention (FutureMe App) on physical activity (PA) and nutrition. The Health Action Process Approach (HAPA) and principles from consumer behavior theory were used to guide the development of the intervention.

The study investigates the impact of avatar-based interventions on PA and food purchasing behavior and aims to understand if avatars can help increase the stand-alone effectiveness of mHealth interventions.

Consumer behavior is a key determinant for chronic disease risk. Mobile health (mHealth) technologies are promising in addressing the rise in risky lifestyle behaviors, as they can be leveraged in large population samples without high human resource or monetary requirements. However, research shows that mHealth technologies are less effective when used stand-alone, meaning without intervention components that require human to human interaction. Leveraging virtual reality in mHealth applications could help increase their stand-alone effectiveness.

Building on behavioral biases, and the health-action-process approach (HAPA), this trial investigates the use of a future-self avatar smartphone intervention (FutureMe app) on consumers' physical activity and food purchasing behavior. A 12-week field experiment aims to show that avatar-based health applications can support behavior change towards more active lifestyles and healthier food choices.

The FutureMe trial has the following objectives:

1. To understand if avatar-based applications are more effective in promoting physical activity and improving food purchasing behavior compared to conventional tracking applications.
2. To understand if providing individualized shopping tips promotes self-efficacy.
3. To understand if providing consequential health behavior feedback increases behavior- related control over future health (outcome expectancy).
4. To understand if avatar-based applications increase intrinsic motivation compared to conventional health-tracking applications.
5. To understand if self-efficacy, outcome expectancy, user engagement or specific types of motivation moderate the effect on PA and foor purchasing.

The study participants recruitment process is supported by a large Swiss health insurance company. The insurer only provides access to potential study participants and is not involved in the design or execution of the study. The insurer has no access to participant study data. Participants are randomized into two groups and either receive the innovative FutureMe intervention or a control intervention consisting of a more conventional nutrition and physical activity tracking app (numeric feedback). Participants will download the respective apps to their personal mobile phone.

Step counts and food purchasing data is collected continuously throughout the trial. The respective psychological constructs (see outcome overview) are collected at baseline and after 12 weeks (end of intervention) via an online questionnaire.

The results of this study enable the evidence-based development of scalable interventions for sustainable physical activity and nutrition behavior change and advance the understanding of the psychological processes behind health behavior change.

Inclusion Criteria:

• Living in Switzerland
• German speaking
• Participating in at least one grocery loyalty program (Migros Cumulus and/or Coop SuperCard)
• Apple or Android smartphone
• Healthy (self-declaration)

Exclusion Criteria

• <18 years
• Increasing PA or adjusting nutrition creates health risk (e.g. diabetic)
• Not living in Switzerland
• Not German speaking
• Not using a grocery loyalty card

Based on the data privacy statement of the study and the ethic's commission application, data cannot be analyzed or shared on an individual participant basis.

Participants are blinded. Investigators are also blinded. The intervention is delivered through a mobile phone application (care provider) and automatically and objectively assessed (through sensor and purchasing data).

Some constructs are assessed via self-reported questionnaire at baseline, 12 weeks and during the 6 month voluntary follow-up (Treatment Self-Regulation Questionnaire (TSRQ); International Physical Activity Questionnaire (IPAQ short-form); Perceived competence maintaining a healthy diet (Williams, Deci & Ryan); Perceived behavior-related control (Renner & Schwarzer)).