Intermittent Fasting and Cardiovascular Risk: What New Research Reveals

Understanding the complex relationship between intermittent fasting and cardiovascular health based on recent research.

By Sneha Tete, Integrated MA, Certified Relationship Coach

Created on Sep 24, 2025

Understanding the complex relationship between intermittent fasting and cardiovascular health based on recent research.

Intermittent fasting (IF) has long been promoted as a dietary strategy for weight loss, metabolic health, and potentially extending lifespan. However, new research is prompting both healthcare professionals and the general public to reconsider the safety of this trend—specifically as it relates to cardiovascular health and long-term risk of heart disease. This article provides a comprehensive look at intermittent fasting, synthesizing new findings with previous evidence to help you make informed choices about your own nutritional approach.

What Is Intermittent Fasting?

Intermittent fasting encompasses several eating patterns that cycle between periods of calorie restriction (or complete fasting) and periods of normal food intake. The most popular forms include:

Time-Restricted Eating (TRE): Limiting food consumption to a daily window, often 8–12 hours (e.g., only eating between 10 a.m. and 6 p.m.).
Alternate-Day Fasting (ADF): Alternating between days of normal eating and days where calories are highly restricted or eliminated.
Modified Fasting Regimens: Such as the 5:2 diet, where individuals eat normally for five days per week and restrict calories on the other two.

The Appeal: Potential Benefits of Intermittent Fasting

Past research has found intermittent fasting may be associated with a variety of health benefits, including:

Reduced body weight and fat mass
Improved blood pressure
Lowered inflammation
Enhanced metabolic markers such as blood sugar and cholesterol levels
Improved endurance and brain function
Short-term reduction in cardiovascular risk factors
Possible neuroprotective effects (lower risk of Alzheimer’s, Parkinson’s, and multiple sclerosis)

These benefits have contributed to the widespread popularity of IF among both health enthusiasts and those at risk of chronic disease.

The Latest Evidence: Raising New Cardiovascular Concerns

Despite previous enthusiasm, new observational research published in early 2024 has cast doubt on the long-term safety of certain intermittent fasting regimens for heart health. Specifically, the focus is on time-restricted eating windows shorter than eight hours per day.

Key Findings from Recent Studies

Increased Cardiovascular Death Risk: An American Heart Association analysis found that individuals restricting food intake to just eight hours a day had a 91% higher risk of death from cardiovascular disease compared to those with longer eating windows (12–16 hours). The effect was strongest among people with pre-existing heart disease.
No Longevity Benefit: Limiting eating to under eight hours per day was not linked to longer life compared to standard meal schedules.
Specific Risks for Vulnerable Groups: In people already diagnosed with cardiovascular disease, an eight-hour eating window was linked with more than a 50% increase in risk of death from stroke or heart disease.
Effect on Cancer Patients: Though IF did not increase cancer mortality risk, those with cancer who ate for more than 16 hours per day had lower cancer mortality risk.
Short Eating Windows May Not Affect Overall Mortality: The risk appeared specific to heart disease, not death from all causes.

How the Studies Were Conducted

The landmark study from 2024 used dietary recall data from over 20,000 U.S. adults ages 18 and over. Participants reported their daily eating windows on two occasions, and researchers tracked health outcomes—including causes of death—over a median follow-up of eight years. Notably:

Nearly all participants using an eight-hour eating window showed increased cardiovascular death risk.
The association remained even after adjusting for health status, lifestyle habits, and demographic factors.
Similar results were found in independent analyses and in presentation at national conferences.

Understanding the Contradiction: Short-Term Gains, Long-Term Doubts

These new findings pose a stark contrast to previous research suggesting benefits:

Early, Short-Term Benefits: Studies and meta-analyses demonstrate that IF can improve several cardiovascular risk factors in the short term, including weight, waist circumference, and blood pressure.
Long-Term Safety Under Debate: The adverse effects—specifically increased cardiovascular mortality with very short eating windows—only appear after prolonged follow-up and may not be captured in short trials.
Lack of Consistency: Not all studies report similar findings, and variables like participant selection, fasting method, and duration complicate direct comparison.

What Could Explain the Risk?

The reasons behind the observed increase in cardiovascular risk with extreme time-restricted feeding are not fully understood. Possible explanations include:

Nutrient Deficiency: Condensing nutrition into a narrow window may lead to poorer dietary balance or skipped meals, resulting in deficiencies in essential macro- and micronutrients.
Stress on the Cardiovascular System: Sudden metabolic shifts, prolonged fasting-induced stress, or suboptimal timing of medication for heart disease may play a role.
Biological Timing: Disrupting normal eating patterns could negatively affect circadian rhythms, metabolism, and hormone cycles which are crucial for cardiovascular health.
Confounding and Bias: Observational studies can be influenced by self-reporting errors, recall bias, and uncontrolled confounding variables (e.g., sicker individuals being more likely to try restrictive diets).
Effects in Vulnerable Populations: Those with existing heart disease or cancer seemed most at risk in these studies, suggesting the need for personalized dietary guidelines.

How Does This Compare to Animal Research?

Rodent studies subjected to long-term intermittent fasting have shown potential downsides at the heart muscle level, such as:

Reduced left ventricular diastolic compliance (the ability of the heart to fill properly)
Increased heart muscle fibrosis (scarring)
Decreased cardiac reserve

These changes, observed after the equivalent of many human years, support the hypothesis that chronic restrictive eating could have unrecognized cardiovascular effects.

Summary Table: Intermittent Fasting Effects on Cardiovascular Health

Fasting Pattern	Short-Term Benefits	Long-Term Risks Reported
Time-Restricted Eating (<8 hrs/day)	Weight loss, lower blood pressure, improved glucose	Increased risk of cardiovascular death; no increase in overall mortality
Alternate-Day Fasting	Reduced body weight, waist circumference, blood pressure	Potential stress on the heart (animal data); lack of robust human long-term data
5:2 Diet (Calorie Restriction 2 days/week)	Improved metabolic markers; easy adherence for some	No major long-term risks identified; more research needed
Normal Eating Window (12–16 hrs)	No fasting-related benefits	Lower risk of heart disease death

What Do Heart Experts Advise?

Given the conflicting evidence, cardiovascular experts urge caution:

Don’t make drastic changes without consultation: Especially those with known heart disease, diabetes, or on medications affecting blood sugar or blood pressure.
Personalize dietary advice: Nutrition needs can differ by age, health status, and overall risk factors.
Prioritize evidence-based practices: Long-standing heart-healthy dietary principles, like the DASH and Mediterranean diets, continue to be validated by prospective randomized trials.
Monitor regularly: Any significant dietary shift should be monitored by a physician, including periodic checks of blood pressure, cholesterol, glucose, and weight.
Avoid overly restrictive approaches: Extreme eating patterns might not be suitable or safe for the majority, and long-term consequences remain under scrutiny.

What to Consider Before Trying Intermittent Fasting

Assess your personal health history, especially if you have cardiovascular disease or are at high risk.
Discuss with your healthcare provider whether IF or restricted eating patterns are appropriate.
Be realistic—focus on sustainable, balanced nutrition rather than quick fixes.
Ensure critical medications for hypertension or other chronic conditions are timed to match your eating windows.
Watch for symptoms of nutrient deficiencies, low blood sugar, dizziness, or fatigue and report them to your doctor.

Red Flags to Watch For

Pre-existing cardiovascular disease
Chronic medical conditions (e.g., diabetes, kidney disease)
Pregnancy or breastfeeding
Elderly individuals at risk of frailty
History of disordered eating

Frequently Asked Questions (FAQs)

Q: Is intermittent fasting safe for everyone?

A: No. Especially for people with pre-existing heart disease, diabetes, chronic illness, or pregnant women, intermittent fasting may carry serious risks. Always consult a healthcare provider before beginning IF.

Q: Does a longer daily eating window reduce heart disease risk?

A: Recent evidence suggests eating across a window of 12–16 hours per day may reduce the risk of cardiovascular death compared to eating within a narrow 8-hour window.

Q: Are there proven long-term benefits to intermittent fasting?

A: While short-term studies show improvements in weight and certain heart risk factors, the long-term effect—especially for heart health—remains uncertain and recent data suggests possible increased risk with extreme restriction.

Q: Should intermittent fasting be used in conjunction with other diets?

A: Any restrictive eating pattern should focus on balanced, nutrient-dense foods. IF should not be seen as a replacement for established healthy eating patterns, such as the DASH or Mediterranean diets.

Q: What should someone already practicing IF do in light of new research?

A: Do not abruptly stop without consulting your medical provider, especially if you have underlying health conditions. Discuss alternative approaches and ensure you’re getting regular medical monitoring.

Key Takeaways for the Future

Long-term safety data on intermittent fasting is evolving: New research suggests previously reported benefits may not extend to cardiovascular mortality and may, in fact, pose risks for some.
Short-term intermittent fasting regimens can improve some heart disease risk factors—but may not translate into improved survival, especially with extreme daily restriction.
Personalized nutrition remains crucial. Consult your doctor before making significant dietary shifts, especially if you have a history of chronic disease or complex medical needs.
The safest path to heart health continues to be a balanced, nutrient-rich diet managed over the long term, combined with exercise, not drastic intermittent fasting regimens.

References: This article is based on a synthesis of current peer-reviewed studies, expert consensus, and the latest updates from research institutes and cardiovascular health organizations. For further reading, please consult recent statements from the American Heart Association and clinical nutrition journals.

References

Author

Sneha TeteBeauty & Lifestyle Writer

Sneha is a relationships and lifestyle writer with a strong foundation in applied linguistics and certified training in relationship coaching. She brings over five years of writing experience to thebridalbox, crafting thoughtful, research-driven content that empowers readers to build healthier relationships, boost emotional well-being, and embrace holistic living.

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