Can Fasting Repair Cardiac Damage after a Heart Attack?

Throughout evolutionary history, organisms developed resilience in response to various environmental stressors, including food scarcity, which shaped the adaptive mechanisms essential for survival. These adaptations, such as the ability to switch between energy sources during times of nutrient depletion, remain embedded in our biology today.

Intermittent fasting taps into this ancient metabolic switch, promoting cellular stress resistance and resilience—inducing metabolic changes that protect against oxidative stress, inflammation, and DNA damage.

By harnessing the power of metabolic switching, intermittent fasting might offer a promising, non-invasive strategy to support heart health and accelerate recovery following cardiac events.

A recent study showed just that — practicing time-restricted eating in the 6 months after a heart attack led to robust improvements in cardiac function and rejuvenation—improvements that weren’t observed in patients who stuck to their regular meal timing. This was accompanied by a significant reduction in blood pressure and body weight.

What might explain these improvements? And should we start to consider fasting as a therapy for heart-attack patients? Let’s explore the study some more.

Fasting has system-wide benefits

The benefits of intermittent fasting and time-restricted eating (TRE) extend beyond weight loss and calorie restriction. In fact, it’s these benefits that I’m much more interested in. For example, time-restricted eating improves blood pressure and glucose regulation, effects that are more pronounced when practicing early time-restricted eating or eTRE. That’s because this pattern of eating aligns with our body’s circadian rhythms in metabolism. Something special happens when we shift our meal timing to earlier in the day that can’t be explained by calorie restriction alone.

Then there’s cancer. Fasting and fasting-mimicking diets (advocated by Dr. Valter Longo) may have anti-tumor effects—they sensitize cancer cells to chemotherapy while protecting normal healthy tissues from treatment-induced adverse events.

It’s tempting to speculate that these resilience-enhancing effects of fasting might extend to other clinical scenarios, for example, to people who’ve suffered a cardiovascular event.

What happens during a heart attack?

Heart attack—also known as a myocardial infarction—occurs when blood flow to a part of the heart is restricted, depriving the heart muscle of oxygen. A lack of blood flow leads to the production of reactive oxygen species. The heart’s cells are forced to switch from aerobic metabolism to anaerobic metabolism, leading to inefficient energy production and the accumulation of metabolic byproducts that cause cellular and molecular damage. Without oxygen, the heart’s cells undergo apoptosis and necrosis, or cell death. As cells die, they release proinflammatory signals that worsen cellular and tissue damage. This cardiac cascade can lead to long-term reductions in the heart’s pumping efficiency and, eventually, heart failure.

Heart attack recovery hinges on more than just reestablishing blood flow—it’s about helping the heart regenerate. This involves rebuilding blood vessels, strengthening heart cells, and adapting to new energy demands. Intermittent fasting has been shown to impact all these critical processes, from promoting angiogenesis to supporting metabolic shifts, positioning it as a potential tool in improving heart healing.

The benefits are not merely theoretical; they’re deeply rooted in the biological stress responses that once helped our ancestors survive in challenging environments. And now they’ve been demonstrated in a randomized controlled study.

Fasting rejuvenates the heart

Just one month after their heart attack, participants assigned to 16:8 time-restricted eating experienced a 6.6% increase in a measure of their heart’s pumping efficiency known as left ventricular ejection fraction (LVEF) compared to a mere 1.5% increase in the regular diet group.

That wasn’t the most surprising part. The improvement in the heart’s pumping efficiency persisted and was even larger at 3 months and 6 months of intermittent fasting—increasing by 8.4% and 10.3%, respectively. The longer the participants practiced intermittent fasting, the more their heart function continued to improve!

In contrast, the heart’s pumping efficiency only improved by 2.2% and 2.5% in the regular diet group at 3 and 6 months, respectively.

Both groups lost some weight and improved their BMI—the intermittent fasting group’s BMI fell by 1.34 kg/m² and the regular diet group’s BMI dropped by 0.58 kg/m²—with the intermittent fasting group experiencing a larger change. The only other major difference was in diastolic blood pressure, which fell from 81 mmHg to 71 mmHg in the intermittent fasting group after 3 weeks and remained at this level for the remaining 6 months. On the other hand, diastolic blood pressure increased from 73 mmHg to as high as 79 mmHg in the regular diet group between 4 weeks and 6 months.

One patient in the regular diet group died during the follow-up period, while zero deaths occurred in the intermittent fasting group.

Meal timing as chronotherapy

What’s so incredible about the findings of this (albeit smaller) study is that the improvements in heart function with fasting were similar to those observed for other clinical treatments. In one study where heart attack patients received stem cell therapy, the heart’s pumping efficiency improved by 8.5% after 4 months. Another study in which stem cells were injected into the patients’ hearts observed a 4.3% improvement in the heart’s pumping efficiency 6 months after their heart attack. Empagliflozin, a sodium-glucose cotransporter 2 (SGLT-2) inhibitor, improved the heart’s pumping efficiency by 4.7% after 6 months.

This means that 6 months of 16:8 TRE (in addition to guideline-based secondary prevention medication including a statin and blood-pressure-lowering therapy) improved cardiac function to the same degree as pharmacological and experimental invasive treatments.

Final thoughts

Could some of the benefits observed with time-restricted eating be due to improvements in body weight and blood pressure? Probably. But since few other cardiometabolic risk factors changed in the intermittent fasting group vs. the regular diet group during the 6-month follow-up period, I think there’s something else going on here, something that probably relates to fasting’s impact on circadian alignment and the cellular repair process.

Our body’s circadian system has a profound influence on the function of our heart. Circadian misalignment elevates cardiovascular risk factors like blood pressure and inflammatory cytokines and dampens the beneficial nocturnal dipping of blood pressure and reduces cardiac parasympathetic modulation. It also impairs cardiac hypertrophy and immune responses that are necessary for healing in the context of heart attack.

In this way, fasting is a form of chronotherapy—an intervention that recognizes timing as an important variable. By helping to realign circadian rhythms, fasting helped heart attack patients recover faster and stronger. And they didn’t even have to change anything about what they ate.

You don’t have to have suffered a heart attack (or know someone who has) to take interest in the implications of these findings. I think that by now you should recognize that meal timing is a very important factor not only for optimizing metabolic health, but also the health of your heart. It’s so important that I included a deep discussion of it in my recent metabolic health presentation.

While fasting may be a helpful tool in recovering from a heart attack, it might also help you avoid one in the first place. It’s all about timing.

You can hear more about my thoughts on intermittent fasting and time-restricted eating in member Q&A session #19!

Watch Q&A Session #19 Now!

Relevant timestamps related to fasting and time-restricted eating:

00:32:26 - What are the acute effects of fasting on inflammation?
00:32:48 - Is 8-hour time-restricted eating compatible with athletes?
00:33:54 - How does Ramadan fasting affect inflammatory biomarkers?
0 0 :35:27 - Does alternate-day fasting reduce inflammation in people with metabolic syndrome?
00:35:50 - The association of changes in fasting blood sugar with C-reactive protein
00:37:00 - What type of time-restricted eating does Rhonda practice?
00:37:50 - Which is better: A weekly 24-hour fast or a quarterly 3-day fast?
00:46:30 - Is there a benefit to being in ketosis when you start a fast?

With appreciation,

Rhonda and the FMF Team

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Fasting has system-wide benefits

What happens during a heart attack?

Fasting rejuvenates the heart

Meal timing as chronotherapy

Final thoughts