Popular Diet Linked to 91% Higher Risk of Cardiovascular Death, Study Finds
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A new study finds intermittent fasting is linked to a higher risk of dying from cardiovascular disease.
The researchers say they’re surprised by the findings.
Experts say more studies are needed.
Intermittent fasting has been a buzzy eating plan for years, but new research from the American Heart Association (AHA) suggests it may not be all that great for your cardiovascular health.
The study, which was presented at an AHA conference this week, analyzed data from two days of eating in more than 20,000 adults and found that people who limited their eating to less than eight hours a day were more likely to die from cardiovascular disease compared to people who had a more typical eating pattern across 12 to 16 hours a day.
Limiting eating to eight hours a day or less is a popular choice of intermittent fasting thanks to the 16:8 eating schedule, which encourages people to fast for 16 hours and have an eating window of eight hours.
For the study, the researchers looked at dietary patterns for people who participated in the annual 2003-2018 National Health and Nutrition Examination Surveys (NHANES) and compared that to data about people who died in the U.S. from 2003 through December 2019.
The researchers found that people who followed a pattern of eating all of their food across fewer than 8 hours per day had a 91% higher risk of death due to cardiovascular disease. In people who already had cardiovascular disease, eating less than 10 hours a day was also linked with a 66% higher risk of death from heart disease or stroke.
Time-restricted eating didn’t lower the risk of death from any cause, the study found.
But messaging around intermittent fasting, including the 16:8 diet, has been that it’s good for your health. Experts break it down.
The data on this has been mixed.
One of the reasons why intermittent fasting has built up such a following is that research has found it’s beneficial for your health. Among other things, intermittent fasting has been linked with improvements in blood pressure, blood glucose, and cholesterol levels. Intermittent fasting has also found to be similarly effective to calorie restriction when it comes to weight loss.
Even the scientists who led the latest study say they didn’t expect what they discovered. “We were surprised to find that people who followed an eight-hour, time-restricted eating schedule were more likely to die from cardiovascular disease,” senior study author Victor Wenze Zhong, Ph.D., a professor and chair of the department of epidemiology and biostatistics at the Shanghai Jiao Tong University School of Medicine in Shanghai, China, said in a statement. “Even though this type of diet has been popular due to its potential short-term benefits, our research clearly shows that, compared with a typical eating time range of 12-16 hours per day, a shorter eating duration was not associated with living longer.”
Cheng-Han Chen, M.D., an interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, agrees that the study findings are a little confusing. “These findings run counter to many previous studies, which find benefits of time-restricted eating to cardiovascular and metabolic health,” he says.
But Ragavendra Baliga, M.D., a heart failure specialist at The Ohio State University Wexner Medical Center, points out that there have been hints in the past that intermittent fasting isn’t always good for heart health. “A previous study showed skipping breakfast was associated with hardening of arteries,” he says.
Why might an eight-hour eating window be linked with cardiovascular disease?
The study didn’t spell out why an eight-hour eating window was linked to a higher risk of developing cardiovascular disease—it just found an association. Dr. Chen also points out that the full study hasn’t been published yet, which may help parse out why this link exists.
But there are a few theories on what could be behind this. “What’s more obvious is that it still matters what someone eats during their eating window,” says Jessica Cording, M.S., R.D., author of The Little Book of Game-Changers: 50 Healthy Habits For Managing Stress & Anxiety. Meaning, if you eat an unhealthy diet during your eating window, it’s not going to do your heart health any favors. Other factors like age, socioeconomics, and lifestyle habits like eating and exercise can play a role, too, Cording points out.
Going without food for longer periods of time can be hard on the body as well, Cording says. “There does seem to be a sweet spot where someone is experiencing the benefits of fasting without putting stress on the body,” she says. “When someone fasts for too long, it can put stress on the body and end up working against their goals.”
But these findings shouldn’t be the end-all, be-all when it comes to intermittent fasting, says Keri Gans, R.D.N., author of The Small Change Diet. “This study is not a randomized double-blind controlled study, which is the gold standard, and it leads us to many unanswered questions,” she says.
Gans also notes that the study only took diet samples from study participants over a few days. “We have no idea how and what they ate the rest of the year, including exact foods and nutrients, how much exercise they engage in, their sleep patterns, and their overall lifestyle,” she points out.
The bottom line
Experts stress that the findings aren’t conclusive at this point, noting that intermittent fasting has still been linked to health benefits. “I would still recommend intermittent fasting for my patients as a way to lose weight, improve blood sugar control, improve cholesterol, and for overall cardiovascular health,” Dr. Chen says.
Dr. Baliga takes a different approach, though. “I usually recommend that individuals eat like a horse for breakfast, puppy for lunch, and a birdie for dinner,” he says. People who eat a hearty breakfast tend to have fewer issues with obesity and cardio-metabolic syndrome, he says. Dr. Baliga also suggests having breakfasts that are high in protein and fiber, with some carbohydrates in the mix. “I also recommend low carbs at night because carbs is a fuel and one does not need fuel at night while sleeping,” he says.
Cording suggests paying attention to your body’s natural hunger cues when it comes to deciding on an eating pattern. If you’re interested in intermittent fasting, she recommends first doing a 12-hour overnight fast and seeing how you feel. “It’s a good introduction to see if you want to extend that window or not,” Cording says.
Of course, if you’re concerned about your cardiovascular health, it’s best to consult a medical professional for more personalized advice.
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