Two heart doctors share if you should be concerned about intermittent fasting heart attacks and weigh in on just who should skip the fast.
Intermittent Fasting and Heart Attacks: Doctors Address the Link
Published on Jan. 01, 2025
Intermittent fasting, a diet that alternates between periods of eating and fasting, is popular due to its touted benefits, including cases of weight loss, improved insulin sensitivity, and better brain health. However, while millions have embraced this eating pattern and reaped the rewards, there’s a concern that’s mirroring what critics have flagged about diets like keto: the impact on heart health.
Heart disease remains the leading cause of death in the United States, with over 800,000 Americans experiencing a heart attack each year, according to data from the Centers for Disease Control and Prevention (CDC). Although intermittent fasting has been linked to health improvements, preliminary studies suggest it may have the opposite effect.
No matter what, diet alone is just one piece of the puzzle when it comes to heart health. “As a cardiologist, I tell my patients that a diet like intermittent fasting is only part of the solution,” says Majid Basit, MD, board-certified cardiologist and interventional cardiologist at Memorial Hermann Health System in Houston.
To reduce your risk of heart disease, it’s essential to adopt a holistic approach. This includes engaging in regular exercise, following a balanced diet rich in whole, nutrient-dense foods, managing stress, avoiding smoking and excessive alcohol consumption, and working closely with your doctor to control key health factors like blood pressure, cholesterol, and blood glucose levels.
Ahead, Dr. Basit and Donald Lloyd-Jones, MD, ScM, board-certified cardiologist and professor of preventative medicine at the Northwestern Medicine Feinberg School of Medicine, explore whether intermittent fasting could contribute to heart attacks. They also share if they recommend it to their patients and which individuals might need to approach this diet with caution.
What is intermittent fasting?
Dr. Lloyd-Jones explains, “Intermittent fasting is more correctly referred to as ‘time-restricted eating,’ where one limits the period during the day when food intake occurs.”
The goal is to extend the fasting interval—typically around 16 hours—to give the liver and metabolic system ample time to process previous meals. This extended break allows the body to reset, preparing it to handle the next intake of calories more efficiently.
“This tends to result in less fat storage in the liver and other tissues,” he adds.
Types of intermittent fasting
“There are many variations of intermittent fasting, including eating only 8 hours per day. Other variations include fasting every other day or only on the weekends,” explains Dr. Basit.
Here are some of the most popular approaches:
16/8 Method (time-restricted eating)
This is the method most people associate with intermittent fasting. It involves fasting for 16 hours a day and eating during an 8-hour window. For example, you might eat between 12:00 p.m. and 8:00 p.m., then fast until noon the next day. It’s known for being flexible and sustainable.
5:2 Diet
With this approach, you eat normally five days a week and significantly reduce your calorie intake (typically to 500–600 calories) on the other two non-consecutive days.
Eat-Stop-Eat
This method involves a full 24-hour fast once or twice a week. For instance, if you finish dinner at 7:00 p.m., you wouldn’t eat again until 7:00 p.m. the next day. While effective for some, it can be more challenging and isn’t suitable for everyone.
Alternate-Day Fasting (ADF)
As the name suggests, this method alternates between days of regular eating and days of fasting or very restricted calorie intake. Some variations allow for up to 500 calories on fasting days.
Spontaneous meal skipping
This involves skipping meals occasionally when you’re not hungry or too busy to eat. It creates fasting periods without adhering to a strict schedule.
Can intermittent fasting cause heart attacks?
The connection between intermittent fasting and heart health remains a topic of ongoing research, with no definitive answers yet. “We have no credible evidence that this is the case. And, to the extent that intermittent fasting may reduce weight and improve insulin sensitivity, there are many potential health benefits,” explains Dr. Lloyd-Jones.
However, a 2024 preliminary study has raised questions, suggesting a possible increased risk of death from cardiovascular disease among those following a time-restricted eating plan.
Still, experts caution against jumping to conclusions based on this data. “Unfortunately, this research relied on people answering questions in a database,” says Dr. Basit. “A more extensive controlled study would be required to show if there are any ill effects of intermittent fasting.”
The study in question, which involved over 20,000 adults, found that those who adhered to an 8-hour eating window had a 91% higher risk of death from cardiovascular disease compared to those following a more typical eating schedule of 12 to 16 hours. The increased risk was especially notable in individuals with pre-existing heart disease or cancer.
For now, experts recommend balancing the potential benefits of intermittent fasting with individual health needs and conditions. Consulting a healthcare provider before making dietary changes is always the best approach.
Potential intermittent fasting side effects
While intermittent fasting is known for its potential health benefits, it’s important to be aware of possible side effects. Here are some key considerations:
- Hunger and cravings: These can lead to irritability and difficulty concentrating, especially in the early stages.
- Low blood sugar: For some, particularly diabetics, fasting may cause dizziness, fatigue, or fainting.
- Nutritional deficiencies: An unbalanced diet during non-fasting periods increases the risk of missing essential nutrients.
- Digestive issues: Some individuals experience bloating, constipation, or diarrhea.
- Fatigue and weakness: A lack of sufficient calories may result in low energy levels.
- Mood swings: Blood sugar and hormonal fluctuations may contribute to irritability or anxiety.
- Sleep problems: Fasting can sometimes disrupt sleep patterns.
- Headaches: Dehydration or low blood sugar levels are common triggers.
- Overeating: Compensatory overeating during eating windows can undermine the benefits of intermittent fasting.
- Hormonal changes: Women may notice disruptions in their menstrual cycles or potential impacts on fertility.
According to Dr. Lloyd-Jones, “It may take some adjustment to eating only between 11 a.m. and 7 p.m. (as one example of intermittent fasting), but for most people, they can overcome that with good water intake.”
If you have conditions such as diabetes or low blood pressure, it’s essential to consult your doctor to ensure your intermittent fasting plan is safe and properly coordinated with your medication schedule.
Who should try intermittent fasting?
Intermittent fasting can be an effective strategy for weight control and even weight loss, but it’s not a one-size-fits-all solution. Both Dr. Lloyd-Jones and Dr. Basit agree that it’s worth considering in certain cases. “As with many things in health behaviors, it works well for some people and doesn’t for others, depending on their daily routines,” says Dr. Lloyd-Jones.
Dr. Basit highlights that intermittent fasting may benefit those who need a structured eating schedule. He advises starting gradually with a more flexible eating plan and keeping healthy, ready-to-eat snacks on hand to manage cravings. However, Dr. Basit cautions against intermittent fasting for people with diabetes, as it may pose challenges in maintaining stable blood sugar levels.
How to practice intermittent fasting safely
Intermittent fasting can be beneficial when done properly. Here are some tips to ensure you practice it safely:
- Start gradually: Begin with shorter fasting periods (for example, 12:12) and increase as your body adapts.
- Stay hydrated: Drink plenty of water during fasting hours.
- Eat nutrient-rich foods: Focus on whole foods like fruits, veggies, lean proteins, and healthy fats. “It is unhealthy to follow an intermittent fasting diet and also eat poor-quality foods,” says Dr. Basit.
- Plan meals ahead: Prepare healthy snacks to avoid impulsive eating.
- Listen to your body: Adjust if you feel dizzy, fatigued, or unwell.
And always remember to consult your doctor. “Regardless of the chosen diet, it is important to seek the advice of your doctor. People with pre-existing heart disease should talk to their cardiologist,” advises Dr. Basit. “Warning signs of heart disease or heart attack include chest pain, chest pressure, shortness of breath, dizziness, and fatigue.”
About the experts:
- Majid Basit, MD, is a board-certified cardiologist and interventional cardiologist at Memorial Hermann Health System in Houston. He is a fellow of the American College of Cardiology and is an adjunct clinical professor at McGovern Medical School at UTHealth.
- Donald Lloyd-Jones, MD, ScM, is a board-certified cardiologist, past volunteer president of the American Heart Association, and professor of preventative medicine at the Northwestern Medicine Feinberg School of Medicine. He completed his cardiology fellowship at Massachusetts General Hospital, where he also joined the junior faculty at Harvard Medical School. In 2004, he moved to Northwestern University, and in 2009, he was appointed Chair of the Department of Preventive Medicine.
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