JMIR Publications

ABSTRACT

Background:

Accurately assessing an individual’s diet is vital in the management of personal nutrition and in the study of the effect of diet on health. Despite its importance, the tools available for dietary assessment remain either too imprecise or expensive for clinical or research use. Image-based methods offer a potential new tool to improve the reliability and accessibility of dietary assessment. Though promising, image-based methods are sensitive to adherence, as images cannot be captured from meals that have already been consumed. Adherence to image-based methods may be improved with prompting via text message.

Objective:

This study aims to quantitatively examine the effect of prompt timing on adherence to a photo food diary, and qualitatively explore the participant experience of dietary assessment in order to inform the design of a novel image-based dietary assessment tool.

Methods:

This study used a randomised cross-over design to examine the intra-individual effect of three prompt settings on the number of images captured in a photo food diary. The prompt settings were control, where no prompts were sent; standard, where prompts were sent at the same time for every participant; and tailored, where prompt timing was specific to each participant. Participants completed a written food record at baseline to determine the timing of tailored prompts, and underwent resting metabolic rate measurement to assess the plausibility of the written food record. Participants were randomised to one of six study sequences, each with a unique order of the three prompt settings, with each three-day photo food diary separated by a wash-out period of at least seven days. The qualitative component comprised semi-structured interviews and questionnaires exploring the experience of dietary assessment.

Results:

Thirty seven people were recruited and 30 participants, (11 male, 19 female; mean (SD) age 30 (10.8) years), completed all photo food diaries. Image rate increased by 0.83 images per day in the standard setting compared to control (P=.23) and increased by 1.78 images per day in the tailored setting compared to control (P=<.001). Sixty two percent of participants preferred to use the photo food diary versus the written food record but reported method-specific challenges with each method, particularly the inability to record via image after a meal had been consumed.

Conclusions:

Tailored prompting improves adherence to image-based dietary assessment. Future image-based dietary assessment tools should use tailored prompting and offer both image-based and written input options to improve record completeness. Clinical Trial: Not registered.