Does Intermittent Fasting Cause Heart Disease? Here’s What Experts Say

In recent years, intermittent fasting has become one of the most popular and widely practiced eating patterns — not just as a method for weight loss, but as a holistic approach to improving overall health.

This dietary strategy focuses on when to eat rather than what to eat, by alternating between fasting periods (no food) and eating windows. During fasting, the body is believed to activate biological mechanisms that enhance fat burning, regulate blood sugar, and improve cellular function.

However, despite many proven benefits, intermittent fasting continues to raise questions — particularly about its effects on heart health, hormones, and women’s health.

Nutritionist Jana Harb explains several key points that should be considered before assuming intermittent fasting causes heart disease.

Does Intermittent Fasting Really Cause Heart Disease?

The study that sparked these concerns is an observational study, not a randomized controlled trial.

That means it identifies a correlation, not a cause-and-effect relationship. Many confounding factors could be influencing the results.

Potential limitations include:

Recall bias: Participants were asked to recall what they ate over just two 24-hour periods — an unreliable reflection of long-term habits.
Selection bias: Some participants may have adopted intermittent fasting because of existing health conditions (like obesity or heart disease), not the other way around — a phenomenon known as reverse causation.
Follow-up duration: The average follow-up was about eight years, which is solid but not long enough to confirm long-term cardiovascular effects.
Food quality and lifestyle factors: The study focused on timing of eating, not on the quality or composition of food, nor on exercise, sleep, or stress — all of which strongly affect heart health.
Muscle mass: Participants with shorter eating windows tended to have lower lean body mass, which can negatively affect metabolism, blood sugar regulation, and bone density over time.

Possible Mechanisms Behind Heart Risks

Although not confirmed, some scientific articles propose mechanisms that might link extreme fasting patterns to cardiovascular risk:

Physiological stress: Prolonged fasting may raise stress hormones (like cortisol), which can increase blood pressure and affect lipid and insulin levels — especially in older adults or people with existing conditions.
Muscle loss: Reduced muscle mass can impair metabolic efficiency and glucose control.
Nutrient deficiencies: Restrictive eating windows might lead to skipped meals and inadequate intake of essential nutrients, vitamins, and minerals.
Poor food choices: Some people eat unhealthy foods (high in sugar, saturated fat, or processed ingredients) within their eating window, negating the potential benefits of fasting.

Limits of the Current Study

The study does not prove causation — it shows an association only.
It has not yet been peer-reviewed or published in a scientific journal; findings were presented as a conference abstract by the American Heart Association.
It did not fully control for key lifestyle factors such as exercise, smoking, sleep quality, or psychological stress.
The definition of “intermittent fasting” was inconsistent — participants were grouped based on self-reported eating durations, not standardized fasting protocols.

Should You Be Concerned About Intermittent Fasting?

According to nutritionist Jana Harb, this study is important and thought-provoking, but not a reason to panic.

It reminds us that intermittent fasting is not universally safe or suitable for everyone, especially without medical guidance.

Rather than rejecting it entirely, the focus should be on individualization and safe application.

Guidelines for Practicing Intermittent Fasting Safely

Consult your doctor or a dietitian, especially if you have heart disease, diabetes, or a family history of cardiovascular problems.
Start gradually — begin with a 12–14-hour fasting window instead of jumping to an extreme 6–8-hour plan.
Prioritize food quality — choose balanced meals rich in fiber, protein, and healthy fats, and low in added sugar and trans fats.
Incorporate resistance training — to preserve muscle mass and maintain a healthy metabolism.
Manage stress, sleep, and activity levels — these lifestyle factors have major impacts on heart health.
Monitor your health markers — such as blood pressure, lipid profile, and blood glucose levels, especially before and during fasting routines.

Final Takeaway

The recent findings suggest an observed association between very short eating windows (less than 8 hours per day) and a higher risk of heart-related mortality — particularly in people with preexisting conditions.

However, there is no solid evidence yet that intermittent fasting directly causes heart disease.

The relationship is complex and influenced by many other factors.

In conclusion, intermittent fasting may offer benefits for certain individuals but isn’t a one-size-fits-all solution.

A personalized, well-balanced approach — under professional supervision — remains the safest path to achieving health and longevity.