Usability and Acceptability of a Mobile Food Record in Free-Living Athletes: A Single-Group Observational Study

Background/Objectives: Accurate assessment of energy intake in free-living athletes is constrained by reporting burden, reactivity, and variable adherence. Image-based dietary assessment methods, such as the mobile food record application (mFR™), may partially address these limitations, although their usability and acceptability in athletes have not been determined. This study evaluated the usability and acceptability of the mFR™ app in free-living athletes and described adherence to a four-day recording protocol. Methods: Twenty athletes (13 males, 7 females; 25.2 ± 7.6 years; 13 classified as Tier 1, recreationally active, and seven as Tier 2 to 3) were asked to record all food and drink over four consecutive days using the mFR™ app installed on their mobile phone device, capturing before- and after-eating images and including a fiducial marker. Acceptability and usability were assessed via an online questionnaire with Likert-scale items and open-ended questions. Adherence was described as recording at least one eating occasion on each of the four target days and as completion of the questionnaire; no adherence criterion was prespecified. Likert responses were summarised using frequencies and percentages, and free-text responses were analysed descriptively at a semantic level. Results: Thirteen participants (65%) recorded at least one eating occasion on all four days and all completed the questionnaire (n = 20). Most participants (85%) agreed they 'found it easy to take photos' of their food and beverage intake. Remembering to capture images before main meals was perceived as manageable (55% agreement), whereas capturing images before snacks was considered challenging (15% agreement). No problems with the app were reported by 90% of participants, and 80% expressed willingness to use the mFR application again. Half of the participants (50%) reported that recording influenced their dietary behaviour, with qualitative responses describing increased awareness of food choices. Conclusions: Usability and acceptability of the mFR™ app were generally rated favourably by participants in this study, whereas adherence declined across the four-day recording period and the completeness of recording within each day could not be established. These findings provide preliminary evidence of acceptability, alongside incomplete adherence and unverified within-day completeness, which require attention before the mFR™ app is used to estimate habitual intake in athletes.