Intermittent fasting probably won’t harm your heart if you do it right

Intermittent fasting has come under scrutiny since the American Heart Association (AHA) released information earlier this week from a study linking this eating pattern to a higher risk of death from heart disease. The findings, which have not been peer-reviewed or published, are controversial.

According to the AHA press release, the study collected data from more than 20,000 adults based on two days of eating as part of a national survey conducted from 2003 to 2018. The researchers compared this information with data collected from people who died in the U.S. from 2003 to December 2019

The researchers concluded that people who had an eight-hour eating interval per day – which mimics the popular 16:8 intermittent fasting diet model – were 91% more likely to die from heart disease than those who ate more than 12 to 16 hours a day, which is a more typical eating pattern.

The study also found that people who already had cardiovascular disease and ate for less than 10 hours a day had a 66% higher risk of dying from heart disease or stroke. Overall, following any form of time-restricted eating pattern did not reduce the risk of death from any cause, according to the findings.

Joseph Dibes, DO, an interventional cardiologist with Northwell Health, urges people to look at the details of studies before jumping to big conclusions.

“I don’t think the American Heart Association did it justice by releasing this summary, which was not completely complete and poorly designed, knowing it would cause a stir,” Dibes told Verywell. “I get phone calls asking if patients should stop their diet and change their lifestyle. There is no reason to do so based on these findings.

There are red flags to look out for

The study hasn’t been published yet — the AHA just shared a press release about it — and it’s also not peer-reviewed.

“Peer review is an important part of the medical publishing process to ensure accurate scientific research and dissemination of research findings in a methodologically sound manner,” Megan Kamat, MD, a cardiologist at UCLA Health, told Verywell.

The data is also based on only two days of dietary intake.

“Two days of dietary data is a limited amount of time when looking at outcomes like cardiovascular mortality and all-cause mortality,” Kamath said. She also noted that there is “limited information” about what people ate during their eating windows. “This would be useful in analyzing this type of study as well as other co-morbidities that these patients have,” she said.

The study relied on survey data, meaning people filled in information about their eating habits. That can be difficult in science because people aren’t always completely honest about what they ate, and they also may not fully remember what they ate or how much, Dybes ​​said.

The study lacked information on other lifestyle risk factors for cardiovascular disease, such as physical activity levels and tobacco and alcohol use.

Dibbs suggested that these findings should be viewed as “preliminary data for a study that may one day become larger.”

There Well Evidence to support intermittent fasting for health

One of the study’s researchers said in the AHA statement that he was “surprised” by the findings, given that most data support the use of intermittent fasting for heart health.

“We have data that shows that intermittent fasting and time-restricted eating are good for your health for many reasons,” Dybe said.

A meta-analysis of human and animal studies published in 2019 found that limiting eating windows was associated with a range of benefits, including lower blood pressure, weight loss and improved life expectancy.

The data also shows that while intermittent fasting can help a person lose weight, it is no more effective than traditional calorie restriction. One study of 139 adults in China who were obese found that those who followed an intermittent fasting diet lost about the same amount of weight and had similar cardiovascular health after one year as people who counted calories .

A randomized controlled trial of 116 people published in 2020 also found no significant differences in weight loss between people who didn’t eat from 8pm to noon the next day (the 16:8 diet) and those who didn’t followed an intermittent fasting diet.

Dybes ​​said intermittent fasting can indirectly help heart health by limiting the amount of insulin spikes you have in a day.

“It’s very good for your metabolism. Your baseline glucose will stay more stable throughout the day,” he said.

Intermittent fasting can also be a useful tool for weight management in some people, simply because maintaining a healthy weight is associated with good cardiovascular health, Daibes added.

Does breakfast matter?

If you’re following an intermittent fasting diet, some scientists think it’s best for your heart health not to skip breakfast, but Kamath said that’s still being researched.

“This is an area that is also being debated in the medical field,” she said. “Most of the thinking behind not skipping breakfast is around the theory that breakfast boosts your metabolism and people who eat breakfast have healthier eating habits, but these haven’t been proven in large-scale studies.”

Dibes agreed that the data is inconclusive about whether skipping breakfast is bad. But “breakfast should be your highest-calorie meal, and the meals that follow should be lower in calories and less heavy,” he said.

Ultimately, the doctors said more research needs to be done to examine the potential benefits and drawbacks of following an intermittent fasting diet for cardiovascular health.

“We’ve seen previous studies show a potential benefit [of intermittent fasting] in terms of obesity, blood pressure and diabetes management, but further work needs to be done to understand this better,” Kamath said. “This is an area of ​​medicine where we’re still trying to figure out what’s best, and more research needs to be done to make a formal recommendation in this space.”

How to practice intermittent fasting in a healthy way

Following a healthy diet when eating is critical, Dybes ​​said.

“You have to eat time-restricted food the right way,” he said. “You can’t say, ‘During these eight hours, I can eat whatever I want.’

He recommends following a balanced, mostly plant-based diet that includes lots of vegetables, with little white meat and fish.

“The Mediterranean diet has been shown repeatedly to be the best for cardiovascular outcomes,” he said.

If you’re planning to follow an intermittent fasting diet, Kamath recommends checking with your doctor first to “take into account individual medical conditions and long-term health goals.”

If your budget allows, it can also be helpful to consult with a registered dietitian to make sure you’re eating well during your eating windows, Dybes ​​said.

“I send quite a few patients to nutritionists to discuss what their food intake should be,” he said.