Duration-dependent cardiovascular responses to prolonged fasting: A systematic review and meta-analysis with meta-regression

Introduction: Prolonged fasting may influence cardiovascular function, but the magnitude and duration dependence of these effects remain unclear. This systematic review and meta-analysis quantified changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) and examined duration-related patterns. Materials and Methods: PubMed, Web of Science, and Scopus were searched for human studies reporting pre–post SBP, DBP, and/or HR after prolonged fasting. Hedges’ g and absolute mean differences were pooled using random-effects models. Duration effects were examined using prespecified subgroups (≤3 vs. > 3 days) and cluster-robust meta-regression. Results: Twenty-four studies were included. Prolonged fasting reduced SBP (k = 23; g = −0.617; 95% CI, −0.824 to −0.409; mean difference, −8.294 mmHg) and DBP (k = 20; g = −0.435; 95% CI, −0.636 to −0.233; mean difference, −3.982 mmHg), and increased HR (k = 11; g = 0.296; 95% CI, 0.009 to 0.583; mean difference, 3.450 beats·min−1). Heterogeneity was high. Between-subgroup differences were significant for SBP and HR but not DBP. Continuous meta-regression identified significant study-level associations between fasting duration and both SBP (β = −0.0547, p = 0.013) and HR (β = 0.1126, p = 0.007), whereas no significant association was observed for DBP (β = −0.0088, p = 0.650). Conclusions: Prolonged fasting was associated with lower SBP and DBP and a small increase in HR. Longer fasting duration was associated with greater reductions in SBP and greater increases in HR at the study level, whereas no significant linear association was observed for DBP. These findings should be interpreted cautiously because the meta-regression analyses were exploratory, substantial between-study heterogeneity was present, and study-level associations should not be interpreted as causal duration–response relationships.