Abstract
BACKGROUND/OBJECTIVES: Appetite is affected by the circadian clock and exhibits diurnal variations. Nevertheless, accurately measuring subjective appetite throughout the day in a free-living setting poses a challenge. This study presents the validation of a novel smartphone application designed to capture, process and analyze circadian appetite fluctuations in a free-living setting. METHODS: Twenty-four healthy participants (ages 38.34 ± 3.2 years) completed this randomized crossover study. Participants completed subjective appetite questionnaires every 30 min in a free-living environment, starting from waking hours until bedtime, using visual analog scale (VAS) via the pen and paper (PP) method and the new smartphone application (App). In addition, on two experimental days, separated by a week of washout, participants were provided either a high-energy breakfast (850 kcal) or a low-energy breakfast (250 kcal). Participants completed the appetite questionnaires using both methods every 30 min for 4 h, followed by an ad libitum lunch. RESULTS: The high-energy breakfast led to significantly increased fullness sensation and decreased hunger, desire to eat, prospective consumption, and appetite score compared with the low-energy breakfast. There was no significant difference between the methods (PP and App) in all measured parameters under both the free-living environment and the controlled environment. Additionally, Bland-Altman analysis revealed a high degree of agreement between the PP and App methods. Moreover, most participants rated the App as the preferred method regardless of age. CONCLUSIONS: Our findings show that the new smartphone application is a valid, reliable tool for measuring subjective appetite, suitable for use in chrononutritional studies conducted in a free-living environment and controlled settings.