Short-term cardiovascular adaptations to Ramadan-associated time-restricted eating in healthy adolescents: a repeated-measures observational study

Ramadan fasting represents a naturally occurring model of time-restricted eating associated with substantial changes in meal timing, hydration patterns, and circadian behaviour. Although cardiovascular responses to Ramadan fasting have been investigated extensively in adults, evidence regarding adolescents remains limited, particularly in populations exposed to low-resource and conflict-affected environments. This study aimed to characterize short-term cardiovascular adaptations during Ramadan fasting among healthy Syrian adolescents using a repeated within-subject design, including evaluation of conventional cardiovascular parameters and derived hemodynamic indices. A community-based repeated-measures observational study was conducted among 120 healthy adolescents (65 males and 55 females; mean age 18 years) attending a specialized secondary school in Daraa, Syria, during Ramadan 1447 AH (2026). Participants underwent standardized cardiovascular assessments during the first week of Ramadan (early fasting phase) and the third week of Ramadan (established fasting phase). Measurements included systolic blood pressure (SBP), diastolic blood pressure (DBP), resting heart rate (HR), rate pressure product (RPP), shock index (SI), body mass, body mass index (BMI), and self-reported fatigue-related symptoms. Within-participant changes were assessed using paired statistical analyses, with additional subgroup analyses according to sex and Suhoor consumption. Compared with the first week of Ramadan, the third week was associated with significant reductions in SBP (129 vs. 113 mmHg; mean difference − 17 mmHg; 95% CI − 20 to − 14; p < 0.001; Cohen’s d = 1.17) and DBP (81 vs. 73 mmHg; mean difference − 8 mmHg; 95% CI − 11 to − 6; p < 0.001; Cohen’s d = 0.65). Resting HR increased significantly (90 vs. 95 beats/min; mean difference + 5 beats/min; 95% CI 3 to 8; p < 0.001; Cohen’s d = 0.45). Similarly, RPP decreased significantly, whereas SI increased during established fasting. No significant changes were observed in body mass, BMI, or overall fatigue-related symptom profiles. Sex-stratified analyses demonstrated comparable reductions in blood pressure between males and females, while the increase in HR was more pronounced among males. Participants who omitted Suhoor demonstrated greater reductions in SBP and DBP and a greater increase in HR compared with those who consumed the pre-dawn meal. Ramadan-associated time-restricted eating was associated with measurable short-term cardiovascular adaptations among healthy adolescents, characterized by reduced blood pressure, increased resting heart rate, and altered derived hemodynamic indices without concurrent changes in body mass, BMI, or subjective fatigue burden. By providing repeated within-person cardiovascular data from an understudied adolescent population in a conflict-affected setting, this study expands current understanding of physiological adaptation during Ramadan fasting. Further longitudinal studies incorporating dietary assessment, hydration measures, autonomic evaluation, and biochemical markers are required to clarify the mechanisms and long-term clinical implications of these responses.