Does Intermittent Fasting Increase the Risk of Cardiovascular Death?

The wellness world has recently been abuzz with claims that intermittent fasting increases the risk of cardiovascular death. Recent findings from a study presented at the American Heart Association’s Epidemiology and Prevention │ Lifestyle and Cardiometabolic Scientific Sessions have prompted a closer examination of this popular eating pattern’s cardiovascular safety. The study highlighted a 91% higher risk of cardiovascular death for participants eating during an 8-hour eating window. 

So, were all the medical professionals who recommended intermittent fasting for its many health benefits wrong the whole time? What are the potential benefits and risks of intermittent fasting on cardiovascular health and what are the limitations of this controversial research? Let’s dive deeper into the topic.

What does this study tell us about intermittent fasting and heart diseases?

The participants, whose average age was 49, were followed for 8 years between 2003 and 2018. In 2003, intermittent fasting was not as popular as it is now. Who started and consistently maintained this dietary model at that time? This is a question mark.

The research was done by telephone interview or face-to-face. The 20,000 people who participated were interviewed twice in the first year about the 24-hour diet. They were only interviewed twice in a year. This model may not be enough to get provide healthy data.

When we look at the study, the participants were categorized into five groups: 8, 8-10, 10-12, 12-16 and over 16 hours. According to this study, the mortality rate from heart disease is higher in the group with an eating time of 8 hours, that is, the group applying the 16:8 method. The rate of loss of life is reported to be higher, especially in cancer patients who are full for 8 hours or less.

When cancer-related mortality rates are examined, it is seen that this figure is lower in people who are full for 16 hours or more. But we don’t know whether these five groups differ from each other. Do people who were full for less than 8 hours and fasted for more than 16 hours have a higher incidence of diabetes, heart health, comorbidities, do any kind of exercise, and what kind of food did they eat during the study? The study does not provide much data on these issues. So we don’t know whether these groups are comparable.

Limitations of the study

While the findings of the study that initiated these discussions are compelling, several limitations of this study must be considered:

• Preliminary study: First of all, this study is a poster presentation, which means it is only a preliminary study and has not yet been published in a peer-reviewed scientific journal. In order for it to be evaluated scientifically, it needs to be sent to scientific journals, the editors need to read and review it and ask some questions. If there are satisfactory answers to the questions, this study will be published in these journals, increasing its scientific value.
• Correlational, not causal: The study establishes a correlation between intermittent fasting and increased cardiovascular risk but does not prove causation. It’s unclear whether intermittent fasting directly contributes to higher cardiovascular death rates or if other uncontrolled factors play a role.
• Lack of detailed dietary analysis: The study did not thoroughly account for the types of foods consumed during the eating window. Dietary quality can significantly influence health outcomes, and without this data, it’s difficult to isolate the effects of the fasting regimen from what is being consumed.
• Generalizability issues: The study’s participants were American adults, and results may not universally apply across different populations with varied dietary habits and health statuses.
• Short-term vs. long-term effects: Most existing research, including this study, focuses on the short-term impacts of intermittent fasting. The long-term cardiovascular effects remain less understood, requiring ongoing research for clearer insights.

Intermittent fasting and heart disease

Historical records from various cultures, including those of Ancient Greece, India, and Egypt, show that fasting was often used as a method for cleansing the body and spirit. These ancient teachings suggested that abstaining from food for a period of time could help treat bodily ailments and improve mental clarity and emotional equilibrium.

Nowadays, intermittent fasting has started to regain its fame back and this fame is not in vain, as most of them are science-backed. In 2020, several scientists published detailed research in The American Journal of Medicine about the effect of intermittent fasting on the heart. The results are quite relieving. It states three mechanisms:

• Oxidative Stress Hypothesis says fasting decreases oxidative stress in the body.
• Circadian Rhythm Theory states the synchronization of eating periods and the heart’s circadian rhythm optimizes glucose and fat usage.
• Ketosis State implies intermittent fasting creates ketogenesis, which decreases blood pressure and fatty tissue.

Benefits of intermittent fasting on heart health

Here’s a detailed look at how intermittent fasting can influence cardiovascular health:

• Improvement in lipid profile: Studies suggest that intermittent fasting has been associated with reductions in total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides, as well as increases in high-density lipoprotein (HDL) cholesterol. These changes contribute to a reduced risk of atherosclerosis, a major contributor to heart disease. Plus, evidence supports that fasting periods improve the way the body processes fats and sugars, leading to better cholesterol profiles and lower levels of circulating fats.
• Weight control: Intermittent fasting can help in weight loss and more importantly, fat burn. Excess body weight, particularly visceral fat, is a well-established risk factor for cardiovascular disease. By aiding in weight management, IF indirectly benefits heart health by reducing the workload on the heart and decreasing the likelihood of obesity-related cardiac complications.
• Reduction in blood pressure: Intermittent fasting can lead to a reduction in blood pressure, which is a significant risk factor for heart disease. This effect may be partly due to weight loss typically seen in individuals who follow an intermittent fasting regimen, as well as a direct influence on the body’s autonomic nervous system, which controls blood pressure.
• Cardiac function and structure: Some studies have shown that intermittent fasting may improve heart rate variability, a measure of the heart’s ability to respond to physiological stressors. It might also influence the heart’s structure by promoting a healthier left ventricular function and reducing heart muscle mass, which is beneficial in certain types of heart disease like hypertrophy.
• Decrease in inflammatory markers: Chronic inflammation is a known risk factor for many forms of heart disease, including coronary artery disease. Intermittent fasting has been shown to decrease levels of inflammatory markers such as C-reactive protein, interleukin-6, and tumor necrosis factor-alpha. This reduction in inflammation may protect heart health by reducing the development of plaque in the arteries.
• Autophagy enhancement: When you take a long break from eating by doing intermittent fasting, your body shifts its focus from digestion to detoxification, a process called autophagy. During autophagy, cells remove damaged and old components and produce new cells. Enhanced autophagy removes dysfunctional organelles or proteins that can lead to cellular stress and improves cellular function, which may protect against heart disease and heart failure.
• Improvement in glucose metabolism: Eating non-stop can cause frequent and severe spikes in blood sugar levels. Over time, this can lead to insulin resistance and stress on the pancreas, which are key factors in the development of type 2 diabetes. Continuous high blood sugar can result in long-term health issues like heart disease, kidney disease, and nerve damage. Whereas intermittent fasting can improve insulin sensitivity and lower blood sugar levels. Better control of glucose levels and insulin response helps in reducing the strain on the heart and vascular system.
• Molecular and hormonal benefits: Fasting triggers a cascade of molecular responses that affect hormonal balance, including the increase of norepinephrine, which aids in weight loss and lipid utilization, and changes in growth hormone levels, which may protect against heart disease.

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Potential risks of intermittent fasting on cardiovascular health

While intermittent fasting has potential benefits for cardiovascular health, it also carries certain risks that may potentially affect heart health, particularly if not properly managed or if you have pre-existing health conditions.

Here are some of the potential cardiovascular risks associated with intermittent fasting:

• Electrolyte imbalance: Fasting for extended periods can lead to disturbances in electrolyte balance, such as sodium, potassium, and magnesium levels. These electrolytes are crucial for maintaining normal heart function and an imbalance can lead to arrhythmias (irregular heartbeats) and, in extreme cases, cardiac arrest, though drinking electrolyte drinks while fasting may help balance your electrolyte levels.
• Activation of the sympathetic nervous system: Intermittent fasting can increase the activity of the sympathetic nervous system, which can raise heart rate and blood pressure. This can be particularly problematic for people with existing hypertension or other forms of heart disease.
• Hypoglycemia: For individuals taking certain diabetes medications, intermittent fasting can increase the risk of hypoglycemia (low blood sugar levels), which can be dangerous and lead to symptoms like palpitations, fainting, and in severe cases, cardiac arrhythmias.
• Negative effects on cholesterol levels: While fasting can improve cholesterol levels in some people, others may experience an increase in LDL (bad) cholesterol and a decrease in HDL (good) cholesterol, particularly during the adaptation phase or due to the types of food consumed during non-fasting periods.
• Increased stress response: Fasting can increase cortisol levels, the body’s primary stress hormone, which in prolonged high levels can lead to negative cardiovascular effects, including higher blood pressure and a higher likelihood of cardiovascular events.
• Nutrient deficiency: Prolonged intermittent fasting, especially if not well planned, can lead to deficiencies in essential nutrients such as vitamins and minerals, which are important for maintaining cardiovascular health.

Conclusion: Balancing the pros and cons of intermittent fasting

Since the benefits of intermittent fasting have so far been supported by many scientific studies, these potential benefits should not be underestimated. However, approaching fasting with caution is also important, as recommended by The American Heart Association too, especially for individuals with pre-existing heart conditions or those taking medication for heart disease.