Effects of Intermittent Fasting on Cardiovascular Health
Recent evidence suggests that intermittent fasting may have mixed effects on cardiovascular health, with potential benefits for metabolic parameters but concerning data regarding cardiovascular mortality when fasting periods are too restrictive (less than 8 hours eating window). 1
Potential Cardiovascular Benefits
- Intermittent fasting has been shown to improve various cardiovascular health indicators in both animals and humans, including blood pressure, resting heart rate, lipid profile, insulin resistance, and glucose levels 1
- Time-restricted feeding during fasting periods can lead to reductions in systolic blood pressure, triglycerides, and fasting glucose levels 1
- Intermittent fasting may favorably modify body composition and reduce ectopic fat deposition, which can indirectly benefit cardiovascular health 1
- Metabolic improvements include reductions in serum triglycerides, total cholesterol, LDL cholesterol, diastolic blood pressure, and increases in HDL cholesterol, particularly in metabolically unhealthy individuals 1, 2
- These benefits may be mediated through multiple pathways, including reduced oxidative stress, optimization of circadian rhythms, and ketogenesis 3, 4
Cardiovascular Risks and Concerns
- According to the most recent 2025 evidence, individuals who restricted their eating to less than 8 hours per day had a higher risk of cardiovascular disease mortality, both in the general population and among those with existing cardiovascular disease, compared to those who ate over a span of 12-16 hours per day 1
- The European Society of Cardiology (ESC) recommends that patients with acute coronary syndrome, advanced heart failure, recent percutaneous coronary intervention, or cardiac surgery should avoid fasting 1, 5
- Certain cardiac conditions including severe aortic stenosis, poorly controlled arrhythmias, and severe pulmonary hypertension are considered high risk for intermittent fasting 1, 6
- Observational studies suggest cardiovascular benefits from extended rather than reduced eating windows, contradicting some earlier assumptions about fasting benefits 7
Weight Loss and Metabolic Effects
- Time-restricted feeding during fasting periods can result in variable weight loss in individuals with overweight/obesity, with greater benefits (>5% weight reduction) when caloric intake is also restricted 1, 2
- Improvements in insulin sensitivity and glycemic responses throughout the day have been documented with intermittent fasting regimens 1, 4
- However, several randomized clinical trials have shown that intermittent fasting is not more effective than standard daily caloric restriction for short-term weight loss or cardiometabolic improvements in patients with obesity 7, 8
Recommendations Based on Cardiovascular Risk
- Low to moderate cardiovascular risk: Intermittent fasting may be permitted with appropriate precautions 1, 5
- High cardiovascular risk: Patients with severe aortic stenosis, poorly controlled arrhythmias, severe pulmonary hypertension, acute coronary syndrome, advanced heart failure, or recent cardiovascular procedures should avoid fasting 1, 6
- If implementing intermittent fasting, an eating window of 8-12 hours appears safer than more restrictive regimens based on recent mortality data 1, 7
Research Limitations
- There are currently no large, randomized controlled trials examining the relationship between intermittent fasting and long-term cardiovascular outcomes 3, 8
- It remains uncertain whether intermittent fasting provides more cardiovascular disease benefit than caloric restriction alone, particularly in the absence of weight reduction 1, 8
- More research on cardiometabolic risk factors, related outcomes, and mechanisms of benefit is strongly recommended 1, 7
Practical Considerations
- When implementing intermittent fasting, choose an eating window that aligns with natural circadian rhythm (preferably 8-12 hours) to minimize potential cardiovascular risks 5, 7
- Focus on improving overall diet quality rather than just restricting eating windows 6, 7
- Individuals with existing cardiovascular conditions should consult healthcare providers before attempting any form of intermittent fasting 1, 5