Skipping Meals, Skipping Beats? Cardiologist Explains The Hidden Heart Risks Of Fasting

Fasting has existed for centuries through religious rituals, cultural traditions, and more recently, as a modern wellness trend. Intermittent fasting, 24-hour fasts, detox fasts and prolonged fasting cycles have all become mainstream, often promoted for weight loss, metabolic benefits and mental clarity. While research does show that short-term fasting may improve insulin sensitivity, reduce inflammation, and support metabolic health, its cardiovascular impact is much more complex, especially for people with pre-existing heart conditions.

For individuals living with hypertension, coronary artery disease, arrhythmias or heart failure, fasting is not always a simple lifestyle experiment. It alters blood sugar regulation, electrolyte balance, hydration status and medication timing, all of which directly influence heart function. As Dr Pavankumar P Rasalkar, Consultant - Interventional Cardiologist, Manipal Hospital Kanakapura Road, notes in his clinical guidance, long fasts can trigger hypoglycaemia, dehydration, lethargy, blackouts, and even rhythm disturbances in vulnerable individuals.

What Happens Inside Your Body When You Fast?

When you begin fasting, the body transitions from using glucose as its primary fuel to mobilising stored fat, a metabolic switch called ketosis. Many people experience improved alertness, reduced bloating and better energy regulation during the early hours of fasting.

But as Dr Rasalkar explains, prolonged fasting can push blood sugar levels dangerously low, leading to symptoms such as dizziness, lethargy, palpitations, or fainting. Hypoglycaemia also disturbs electrolyte balance, particularly sodium, potassium and magnesium, which are essential for maintaining a stable heartbeat.

Peer-reviewed research supports this. The National Institutes of Health notes that electrolyte imbalance can disrupt cardiac conduction, potentially triggering arrhythmias. Additionally, fasting-induced dehydration can reduce circulating blood volume, stressing the heart and increasing the risk of low blood pressure or syncope.

Why Fasting Can Be Risky For People With Heart Conditions

Dr Rasalkar highlights that fasting becomes risky when underlying cardiac problems are present. Several mechanisms explain this:

1. Medication Timing Gets Disrupted

Many heart medications, like beta blockers, anti-arrhythmics, blood thinners, antihypertensives, must be taken with food or at specific intervals. Skipping meals may:

• reduce medication absorption
• make doses more potent on an empty stomach
• increase side effects such as dizziness, low blood sugar or low blood pressure

Abruptly missing doses, especially medications for hypertension or arrhythmias, can trigger rebound symptoms, including raised blood pressure or dangerous rhythm disturbances. This aligns with guidance from the American Heart Association, which states that medication adherence is crucial for cardiac stability.

2. Electrolyte Imbalance Raises Arrhythmia Risk

Potassium, magnesium and calcium levels fluctuate when fasting is prolonged. The British Heart Foundation confirms that even mild electrolyte shifts can provoke palpitations or arrhythmias in vulnerable individuals.

3. Heart Failure Patients Face Higher Risk

People with heart failure often rely on strict fluid management. Fasting-related dehydration or sudden fluid shifts can worsen symptoms.

4. Stress Hormone Spikes

Long fasting periods increase levels of adrenaline and cortisol, which can raise heart rate and blood pressure.

Doctor's Expert Advice: How To Fast Safely If You Have A Heart Condition

Dr Pavankumar P Rasalkar emphasises that fasting can be done safely if cardiac patients take the right precautions. His recommendations:

1. Stay Hydrated: Drink sufficient water before and after fasting hours. Hydration maintains blood pressure and reduces cardiac strain.
2. Never Skip or Alter Medications Without Medical Guidance: Consult your cardiologist about whether fasting is safe for you, and how to adjust timing or dosage if needed.
3. Eat Balanced, Nutrient-Dense Meals During Non-Fasting Hours: Choose foods rich in potassium, magnesium, and protein to maintain electrolyte stability and muscle function.
4. Avoid Long Fasting Durations: Dr Rasalkar advises heart patients to avoid fasting longer than 12 hours, as extended fasts can cause sharp drops in blood sugar and blood pressure.
5. Break the Fast If Warning Symptoms Appear: Stop fasting immediately and seek help if you experience chest discomfort, dizziness, palpitations, fainting, severe weakness. These may indicate hypoglycaemia or arrhythmia.

Fasting can be beneficial for some people, but it is not universally safe particularly for those with heart disease, arrhythmias, hypertension or heart failure. The metabolic and electrolyte shifts that occur during prolonged fasting can strain the cardiovascular system and interfere with essential medications. As Dr Pavankumar P Rasalkar stresses, heart patients must approach fasting with caution, planning, and medical supervision. With proper hydration, nutrition, medication timing and shorter fasting windows, many individuals can fast safely, but the priority should always be your heart's health.

Disclaimer: This content, including advice, provides generic information only. It is in no way a substitute for a qualified medical opinion. Always consult a specialist or your own doctor for more information. NDTV does not claim responsibility for this information