Accepted for/Published in: JMIR Research Protocols
Date Submitted: May 4, 2026
Date Accepted: Aug 31, 2026
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Reminder Strategies to Improve Meal-Logging Adherence: Micro-Randomized Trial Protocol
ABSTRACT
Background:
Accurate measurement of lifestyle factors is central to understanding how daily behaviors act as risk factors or protective buffers to non-communicable diseases. While wearable devices enable passive monitoring of physical activity or sleep, nutritional intake still depends on active participant input such as manual dietary logs or image-based recordings. Adherence to such logging tasks often declines rapidly, impacting data completeness and clinical utility. Theory-based reminders drawing on loss-framing or logging consistency feedback (i.e., tracking streaks) can improve adherence to lifestyle data collection, but effects of these strategies on repeated dietary logging remain unclear.
Objective:
To examine examines the effects of two theory-driven reminder strategies, loss-framing and logging consistency, on adherence to repeated, image-based meal-logging.
Methods:
We employ a micro-randomized trial (MRT) embedded within a 4-week observational lifestyle phenotyping study in Switzerland (N=200, age ≥45, BMI ≥25 kg/m²). Participants photograph their meals at each mealtime (breakfast, lunch, dinner) using a mobile app over 28 days. A decision point is scheduled prior to participant-defined habitual mealtimes. Participants are randomly assigned with equal probability to: (1) a reminder emphasizing loss of a daily financial reward for not logging ("loss-framing"), (2) a reminder providing feedback on recent logging consistency ("logging consistency"), or (3) a neutral reminder ("active control"). The proximal outcome is whether the participant logs a meal within two hours of receiving a reminder. Participants earn a daily financial reward contingent on meal logging completion. To estimate intervention effects, we will use marginal excursion effect models for binary outcomes, adjusting time-varying covariates (e.g., day in study) and baseline covariates (e.g., age, gender). Ethics approval for this study was granted by the Cantonal Ethics Committee of Eastern Switzerland (BASEC ID: 2025-00972).
Results:
Enrollment began in November 2025, and the study was initiated on December 8, 2025, with an anticipated completion date of January 2027.
Conclusions:
By clarifying the proximal effects of loss-framed and consistency-based reminders, findings will inform the design of future digital health studies to improve meal-logging adherence in daily life. This work contributes to the development of scalable, theory-driven reminder strategies for enhancing dietary data quality in observational and interventional research. Clinical Trial: ClinicalTrials.gov NCT07555262; https://clinicaltrials.gov/study/NCT07555262 ClinicalTrials.gov NCT07373418; https://clinicaltrials.gov/ct2/show/NCT07373418
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Copyright
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