Relative validity of the food recording app Libro, adapted for young people: a crossover study (Preprint)

Abstract

Dietary intake plays a crucial role in health research, yet existing methods for its measurement present several challenges such as participant burden, lengthy recording processes and human errors, and do not account for age-specific variations.

This study assessed the relative validity of a food recording program within Libro, a real time diet tracking app, compared to a 24-hour recall method, specifically Intake24, among a group of young people sampled from a population vulnerable to eating misbehaviour. The food recording program was customized for the target population based on feedback gathered from a focus group.

The relative validity of Libro was tested by adopting a cross-over design which recorded food intake over a period of 3 non-consecutive weekdays and 1 weekend day with both methods. The primary outcome was concordance of total energy intake between the two methods, with secondary outcomes focusing on intake of protein, carbohydrates, fats, free sugars, fibre, and trans-fatty acids. Test-retest validity was assessed per each method with the intraclass correlation coefficient; a Bland-Altman plot and t-test were performed to test agreement at group level; correlation coefficient and cross-classification were performed to assess agreement at individual level.

The average intraclass correlation coefficient for energy intake measured by Libro over four days was 0.85 (95% CI: 0.76-0.91). Compared to Intake24, average energy intake recorded using Libro was significantly lower (mean difference: -554 Kcal, 95% CI: -804.1 to -305.6 Kcal, p < 0.001), potentially driven by the reduced reporting of foods rich in free sugars. The correlation coefficient for average energy intake measured by Libro vs Intake24 was 0.32 (p = 0.03), with only 27.7 % of subjects classified in the same quartile with both methods (κ = 0.31, p = 0.03). Concordance varied across specific dietary component measures.

While Libro had good test-retest reliability if adopting a multi recall method, it underreported energy and other aspects of dietary intake, along with poor classification performance compared to Intake24. These results might be partially explained by the absence of pop-up memory prompts (which are a feature of Intake24), and the inability to customise the notification system throughout the day. We also suggest that a user-centred interface, graphic design, and implementation of strategies to enhance motivation may play a role in affecting participants compliance and should be improved to enhance the overall food recording process.