When hunger and thirst part ways: a longitudinal comparison of men and women across the Ramadan fasting-recovery cycle, with non-fasting controls.

INTRODUCTION

The Ramadan fast imposes abstinence from food and water during daytime for 28-29 days, providing an ecological model of prolonged intermittent dry fasting. Longitudinal data characterizing hunger, thirst, and hydration trajectories across fasting and recovery remain limited.

METHODS

In the 2021-2023 Circadian Ramadan (CiRAM) Study (registered in the Open Science Framework, DOI: https://doi.org/10.17605/OSF.IO/ETMU4), self-reported daily peak hunger and thirst levels, daily peak appetite timing, and estimated daily fluid intake were assessed in a prospective longitudinal cohort of 287 Ramadan-observing Israeli Muslims (mean age 26.89 ± 6.77, 58.2% female) and 76 ethnically comparable controls (mean age 24.28 ± 6.55, 63.2% female) at five time points spanning pre-, early-, and late-fasting and two post-fasting timepoints.

RESULTS

Hunger declined significantly at Ramadan onset and remained suppressed one month post-Ramadan (medium effect, η2 = 0.067), with a more rapid within-sex decline in women (η2 = 0.098 vs. 0.038). The sexes differed significantly only at one-month recovery, when women reported higher hunger (medium effect, Cramér's V = 0.21). Thirst rose incrementally, remained elevated through late fasting, then fell below pre-Ramadan baseline after fasting (medium effect, η2 = 0.071). Peak appetite timing was delayed during Ramadan and returned to baseline post-Ramadan (small effect, η2 = 0.052). Fluid intake rose post-Ramadan, earlier in men (small effect, η2 = 0.04). Normalized intake was higher in women throughout in the Muslim group and at 3 timepoints in controls. Controls showed no comparable transition-specific changes, though a small omnibus reduction in hunger was observed (small effect, η2 = 0.051).

DISCUSSION: Over Ramadan and recovery, partially dissociable trajectories were observed: progressive hunger suppression contrasted with an incremental rise in thirst, alongside a circadian delay in peak appetite timing. Sex differences were limited to hunger and fluid intake. The absence of comparable changes in controls suggests these trajectories are not attributable to seasonal variation alone, with effects on hunger, thirst, and fluid intake persisting one month after Ramadan.