JMIR Publications

ABSTRACT

Background:

Establishing a methodology to assess nutritional behavior comprehensively and accurately is extremely challenging. Mobile technologies such as mobile applications (apps) enable eating events to be assessed in-the-moment in real-time, which reduces the memory biases that are inherent in retrospective food records. However, users might find it challenging to take images of the food they consume at every eating event over an extended period of time, which might lead to incomplete eating event records (“missing events”).

Objective:

The three present studies assessed how often eating events (meals and snacks) were missed over a period of 8 days in a naturalistic stetting by comparing the number of recorded events (1) to the number of normative expected events, (2) over time, and (3) to recollections of missing events.

Methods:

The participants in three eating event-based EMA studies using mobile image-based dietary assessments (MIDA) were asked to record all eating events for 8 consecutive days (Study 1, N=38, 1,070 eating events; Study 2, N=35, 934 eating events; Study 3, N=110, 3,469 eating events). Study 1 used a “basic” app, Study 2 included one fixed reminder and an addendum feature, and Study 3 included two fixed reminders and the option to record skipped meals. Later recordings of missed events and their reasons were also assessed.

Results:

Overall, the 183 participants reported 5,473 eating events (3,803 main meals, 1,505 snacks, 165 afternoon teas). While the momentary adherence rate as indexed by a comparison with normative expected events was generally high across all three studies, a differential pattern of results emerged with a higher rate of logged meals in the more technically intensive Study 3. Multilevel models for the logging trajectories of reported meals in all three studies showed a significant, albeit small decline over time (b = -0.11- -0.14, p < .001, pseudo-R² = .04-.06), mainly due to a drop in reported snacks between days 1 and 2. Intra-class coefficients indicate that 38% or less of the observed variance was due to individual differences. The most common reasons for missing events were being engaged in competing activities and technical issues, while situational barriers were less important.

Conclusions:

The three different criteria (normative, time stability and recalled missing events) consistently indicated missing events. However, given the intensive nature of diet EMA protocols, the effects sizes were rather small and the logging trajectories over time were remarkably stable. Moreover, the actual state of the individual and the context seem to be of greater influence on adherence rates than stable individual differences, which emphasizes the need for a more nuanced understanding of the factors that affect momentary adherence.