- Restricting eating to a brief 8-hour window daily could result in a higher risk of death from heart attack and stroke, according to a new study.
- Researchers report that people who practice this time-restricted eating plan also had poorer outcomes if they had existing cardiovascular disease or cancer.
- This study was observational, so it is hard to draw definitive conclusions, but it does add to the growing body of studies on the pros and cons of time-restricted eating.
People who follow one of the more popular time-restricted eating strategies, 16:8 intermittent fasting, may have a higher risk of cardiovascular disease and death than those who don’t fast or employ other fasting techniques, according to a new study.
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Intermittent fasting — where people purposefully restrict the hours during which they consume their daily calories —has become a trendy way to help lose weight, improve cholesterol, increase metabolism, and potentially reduce the risk of certain chronic diseases.
However, this new research casts some doubt as to the long-term health benefits of this eating strategy.
Researchers looked at a group of 20,000 adults who answered questions about their dietary patterns for the annual 2003-2018 National Health and Nutrition Examination Surveys (
The researchers said they found that the participants who practiced 16:8 intermittent fasting were 91% more likely to have died from cardiovascular disease than those who didn’t practice this type of fasting.
They also reported that those with existing cardiovascular disease who consumed all their calories between an 8 and 10-hour frame also had a 66% higher risk of dying from heart disease and stroke.
In addition to the fact they found no benefit to time-restricted eating on death risk in general, the researchers also noted that among people with cancer, those who did not practice fasting and consumed their daily calories over a 16-hour frame actually had a lower risk of cancer mortality than those who ate in a more restricted time frame.
“The study included a large sample size and had a longitudinal design, looking at the individuals over an average of 8 years. However, the dietary information collected was by two 24-hour recalls at the time of enrollment, which can limit the study’s findings and accuracy given that dietary patterns can change over a period of time,” Michelle Routhenstein, RD, CDN, a preventive cardiology dietitian who wasn’t involved in the study, told Medical News Today.
In addition, observational studies, by their very nature, cannot prove cause and effect.
Those aren’t the only limitations, added Dr. Cheng-Han Chen, an interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in California who was not involved in the study.
“These findings run counter to many previous studies which find benefits of time-restricted eating to cardiovascular and metabolic health,” he told Medical News Story. “The full study has not yet been published, but there may be differences in the baseline characteristics of the time-restricted eating groups that could account for these surprising findings. The results may be confounded by differences in baseline demographics and characteristics between the TR groups (especially between the less-than-8-hour group and the others), as well as bias in a participant’s recall of their eating patterns.”
Even given their limitations, the research findings have plenty of merit for further investigation, experts say.
They said there is little long-term human research on intermittent fasting, so studies like this are crucial to deepening our understanding of the practice.
“This study is a great example of how short-term outcomes don’t always predict the long-term impact,” said Dr. Avantika Waring, the chief medical officer at cardiometabolic care telemedicine company 9amHealth who wasn’t involved in the study.
“It may be that intermittent fasting helps people lose weight in the short term and improves some metabolic markers, but doesn’t provide lasting cardiovascular benefits,” Waring told Medical News Today.
Ultimately, whether you want to try intermittent fasting of any kind also depends on you, the advice of your doctor, and your short-term and long-term goals.
“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,” Chen said.
“The best dietary recommendation for anyone seeking to improve their health is one that they are able to do consistently,” Maggie Evans, RDN, the manager of nutrition programs at 9amHealth, told Medical News Today. “The best dietary patterns are specific to the individual’s medical history, health goals, and factors affecting their ability to succeed (socioeconomic status, budgets, lifestyle, etc.).”
Waring agreed.
“This study is overall quite exciting, and I know that many of my patients have had success losing weight by limiting their eating window, but the focus should remain on the type of food consumed — i.e., unprocessed and nutrient-dense,” she said. “And until we have more details about this study, and ideally a randomized controlled trial to study the actual effect of intermittent fasting beyond associations, I would not recommend this over other eating patterns.”