Fasting and blood pressure
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Fasting and Blood Pressure: Effects and Mechanisms
Blood Pressure Reduction with Fasting and Calorie Restriction
Multiple studies show that fasting and energy-restricting diets can significantly lower both systolic and diastolic blood pressure in adults. Meta-analyses report average reductions in systolic blood pressure (SBP) by about 1.9–4.1 mmHg and diastolic blood pressure (DBP) by about 1.3–2.3 mmHg, with fasting regimens often producing greater effects than simple calorie restriction. Shorter interventions (up to 12 weeks) and fasting protocols tend to yield the most pronounced reductions in blood pressure Kord-Varkaneh2020Mohammadzadeh2025.
Impact of Long-Term and Intermittent Fasting
Long-term fasting, even up to 41 days, has been shown to decrease blood pressure, especially in people with hypertension. In hypertensive individuals not on medication, reductions in SBP and DBP can be substantial—up to 24.7/13.1 mmHg in those with the highest baseline blood pressure. Even some medicated hypertensive patients were able to reduce or stop their medication during fasting, while normotensive individuals experienced only modest changes . One-day intermittent fasting also led to a decrease in daytime SBP in hypertensive patients, with no significant hypotension or adverse effects reported .
Religious and Fasting-Mimicking Diets
Ramadan fasting, a form of intermittent fasting practiced for a month, is associated with reductions in both SBP and DBP by about 3–7 mmHg and 2–3 mmHg, respectively. These benefits are seen in healthy individuals and those with hypertension or diabetes, but not in patients with chronic kidney disease. The effects are independent of weight loss or changes in body composition, suggesting a direct benefit of fasting on blood pressure regulation .
Fasting-mimicking diets (FMD), which simulate the effects of fasting while allowing some food intake, also significantly reduce SBP and DBP, as well as other cardiovascular risk factors like HbA1c and IGF-1 .
Mechanisms: Gut Microbiome and Metabolic Changes
Fasting alters the gut microbiome, increasing beneficial bacteria and metabolites that are linked to lower blood pressure. In metabolic syndrome patients, fasting not only reduced blood pressure and body weight but also decreased the need for antihypertensive medications. These changes were sustained for months after the intervention . Animal studies confirm that intermittent fasting can prevent the development of hypertension by modifying the gut microbiota and related metabolic pathways, such as bile acid metabolism .
Other mechanisms include improved insulin sensitivity, reduced body weight, and modulation of the local renin-angiotensin system in the heart, all contributing to lower blood pressure and better cardiovascular health Camelo2019Wan2003.
Safety and Tolerability
Fasting is generally well-tolerated, especially in overweight or hypertensive individuals. Most report good subjective well-being during fasting periods, and no significant adverse effects like hypotension have been observed in short-term studies Grundler2020Isayeva2022. However, individuals with very low baseline blood pressure may experience slight increases, and those with chronic kidney disease may not see the same benefits Grundler2020Al-Jafar2021.
Conclusion
Fasting—whether intermittent, long-term, religious, or mimicked by specific diets—consistently lowers blood pressure, especially in people with hypertension or metabolic syndrome. These effects are mediated by changes in metabolism, the gut microbiome, and cardiovascular regulatory systems. Fasting is generally safe and well-tolerated, making it a promising non-pharmacological approach for blood pressure management and cardiovascular risk reduction Kord-Varkaneh2020Grundler2020Al-Jafar2021+6 MORE.
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