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Lifestyle Medicine: Intermittent Fasting

Writer's picture: Maryal ConcepcionMaryal Concepcion

Is Fasting for More Than 14 Hours Too Long?



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Intermittent fasting (IF) is gaining popularity for its potential health benefits, including weight loss and improved heart health. But for people with heart conditions, fasting for extended periods may not always be the best idea. Let’s dive into why fasting longer than 14 hours might be risky for heart patients.


Why 14 Hours Might Be the Limit

Research suggests that fasting for more than 14 hours could increase risks for patients with heart conditions. For example, a study found that nighttime fasting durations longer than 14 hours were linked to higher rates of cardiovascular problems and even early death. This highlights the importance of keeping fasting periods manageable.


Some trials, like the INTERFAST-MI study, explored longer fasting (16 hours) in heart patients under strict monitoring and controlled conditions. While there were some benefits, these results shouldn’t be applied without caution, especially in real-world settings where patients don’t have constant medical supervision.


Risks of Fasting for Heart Patients

  1. Electrolyte Imbalance and DehydrationFasting for long periods can upset the balance of important minerals like potassium and sodium. For heart patients, this can lead to arrhythmias (irregular heartbeats) or other cardiac issues.

  2. HypoglycemiaIf you have diabetes or take medications to lower your blood sugar, fasting could cause dangerous drops in glucose levels. Low blood sugar can increase the risk of heart attacks or other cardiovascular events.

  3. Nutritional DeficienciesExtended fasting may mean missing out on key nutrients that your body—and your heart—need to function properly.

  4. Higher LDL CholesterolSome studies suggest that fasting might increase "bad" cholesterol (LDL-C) levels, which could raise the risk of heart disease.

  5. Increased Risk of Heart EventsEvidence shows that being in a fasting state could make the heart more vulnerable during a heart attack. Staying in a fed state might actually offer some protection.

  6. Risks for Older AdultsIf you’re older or have advanced heart disease, fasting could be even more challenging. It might worsen existing conditions or lead to complications like fainting or dizziness.


Is Fasting All Bad?

Like most things, it depends! When done carefully, fasting can offer some heart health benefits, like:

  • Lowering blood pressure

  • Reducing cholesterol

  • Improving insulin sensitivity


Fasting methods like time-restricted eating (e.g., eating within an 8-hour window) have shown mild weight loss and better management of risk factors like triglycerides and inflammation.


What’s the Takeaway?

For people with heart conditions, fasting longer than 14 hours should be approached with caution and medical guidance. The risks—like dehydration, low blood sugar, and increased cardiovascular events—can outweigh the benefits without proper supervision.


If you’re considering intermittent fasting, consult your doctor to tailor a plan that keeps your heart safe while helping you meet your health goals. Remember, moderation is key!

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A Direct Primary Care Clinic in Arnold, CA

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