Ramadan fasting lowered blood pressure and raised heart rate in Syrian adolescents

Healthy adolescents in Daraa, Syria, showed measurable cardiovascular changes during Ramadan fasting, according to a repeated-measures observational study published in BMC Nutrition. Compared with the first week of Ramadan, the third week was associated with significant reductions in both systolic and diastolic blood pressure, alongside a modest but consistent increase in resting heart rate.

Because every participant served as their own control, the within-person design reduces the influence of individual differences that often complicate comparisons between separate groups.

Systolic blood pressure fell from an average of 129 mmHg in the first week to 113 mmHg in the third week, a mean difference of −17 mmHg with a 95% confidence interval of −20 to −14 mmHg and a p-value below 0.001. The effect size was large, with Cohen’s d of 1.17. Diastolic blood pressure dropped from 81 mmHg to 73 mmHg, a mean difference of −8 mmHg (95% CI −11 to −6; p < 0.001; Cohen’s d = 0.65).

Resting heart rate moved in the opposite direction, rising from 90 to 95 beats per minute, a mean increase of 5 beats per minute (95% CI 3 to 8; p < 0.001; Cohen’s d = 0.45). The researchers also examined two derived hemodynamic indices. The rate pressure product, which reflects cardiac workload, decreased significantly, while the shock index, the ratio of heart rate to systolic blood pressure, increased during established fasting.

Notably, these cardiovascular shifts occurred without concurrent changes in body mass, body mass index, or self-reported fatigue-related symptoms. The absence of weight change suggests the blood pressure and heart rate adaptations were not simply a byproduct of altered body mass over the study window, although the observational design cannot establish the underlying mechanisms.

Subgroup analyses revealed some differences between participant groups. Sex-stratified analyses showed comparable reductions in blood pressure among males and females, but the increase in heart rate was more pronounced among males. Participants who omitted Suhoor, the pre-dawn meal, demonstrated greater reductions in both systolic and diastolic blood pressure and a greater increase in heart rate compared with those who consumed it, hinting that hydration and meal timing may modulate the cardiovascular response.

Ramadan fasting is a naturally occurring model of time-restricted eating, involving substantial changes in meal timing, hydration patterns, and circadian behavior. Cardiovascular responses to Ramadan fasting have been studied extensively in adults, but evidence in adolescents remains limited, particularly in populations exposed to low-resource and conflict-affected environments. By providing repeated within-person cardiovascular data from an understudied adolescent population, the study addresses a gap in the existing literature.

The authors caution that 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. As an observational study without such measures, it characterizes short-term physiological adaptation but cannot explain why blood pressure fell or heart rate rose, nor determine whether the changes persist beyond the fasting month or carry clinical significance for healthy adolescents.

Subject of Research: Short-term cardiovascular adaptations to Ramadan fasting in healthy Syrian adolescents

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

Article References: Jabr, S. J., Al-Karad, D., Alrefaai, K. M., Alatma, O. A. A., & Nabulsi, A. (2026). Short-term cardiovascular adaptations to Ramadan-associated time-restricted eating in healthy adolescents: a repeated-measures observational study. BMC Nutrition. https://doi.org/10.1186/s40795-026-01489-9

Image Credits: AI Generated

DOI: 10.1186/s40795-026-01489-9

Keywords: Ramadan fasting, time-restricted eating, adolescents, blood pressure, heart rate, hemodynamics, Syria, observational study, rate pressure product, shock index, Suhoor, cardiovascular adaptation