Many people say
intermittent fasting has helped them to lose weight. But the practice may mask a dark side that could potentially put your life at risk.
Dieters who limit their eating to a window of less than eight hours during a 24-hour period are 91% more likely to die from cardiovascular disease than folks who eat across a period of 12 to 16 hours a day, according to a new study.
The findings were based on an analysis of the dietary patterns and lifespans of more than 20,000 U.S. adults, and the research was presented at the American Heart Association's Epidemiology and Prevention Lifestyle and Cardiometabolic Scientific Sessions 2024 in Chicago.
This study raises new questions about the health benefits and potential risks of intermittent fasting.
What is intermittent fasting?
Intermittent fasting involves restricting the times when you eat to specific periods during the day. The key feature of this approach is short periods of eating followed by longer periods of abstaining from all foods.
Many people who follow an intermittent fasting regimen stop eating several hours before bedtime, or delay eating for hours after they wake up. Assuming a person sleeps for seven hours, adding a few hours of fasting to either side of the sleep cycle can extend the window of fasting to 10 or 12 hours, or even longer.
Other people fast for much shorter periods, such as four hours. Or they fast on alternate days or develop another schedule that works for them.
One of the most common types of intermittent fasting is the “16:8” schedule, where you eat all foods within an eight-hour period and fast for the remaining 16 hours of the day.
While some people fast for religious or general health reasons, many others today follow an intermittent fasting protocol in the hope that it will help them to lose weight.
Health benefits and risks of intermittent fasting
As intermittent fasting has become more popular among folks trying to lose weight, success stories have abounded.
One recent review of 40 studies found that
intermittent fasting typically helps people to lose between 7 and 10 pounds over a 10-week period.
In addition, earlier studies have found health benefits associated with intermittent fasting, including improved:
- Blood pressure
- Blood glucose
- Cholesterol levels
However, the researchers involved with the new study did not find any evidence of a link between intermittent fasting and a reduction in the overall risk of death from any cause.
In addition, the new research raises a major red flag about the potential cardiovascular dangers that also might lurk behind the practice of intermittent fasting.
The researchers noted their surprise at the findings, and said the data should raise concerns for those who follow an intermittent fasting approach, especially if they have an existing heart condition or have been diagnosed with cancer.
For people who have been diagnosed with cardiovascular disease, restricting eating to a window of between eight and 10 hours a day was linked with a 66% higher risk of death from heart disease or stroke, according to the researchers.
By contrast, those who have been diagnosed with cancer and who extend their window of eating beyond 16 hours each day have a lower risk of dying from the disease.
Despite the troubling findings of the study, the researchers cautioned that although they found an association between restricting eating to an eight-hour window and a higher risk of cardiovascular death, they
could not say conclusively that time-restricted eating actually causes such deaths.
For example, it is possible that poor nutrient quality in the diets of those included in the study was responsible for what researchers found.
Is intermittent fasting a good choice for you?
Amanda Sauceda, a California-based registered dietitian and owner of The Mindful Gut approach to gut health, says she understands the appeal of intermittent fasting.
"I think part of the allure with intermittent fasting is the clear-cut guidelines,” she says. “When it comes to nutrition, it’s easy to want to pick a straightforward way of eating.”
However, Sauceda says intermittent fasting might not be the best way to achieve weight-loss goals.
“I can see how for some this may work well for them, and it feels good in their body,” she says. “But ultimately, I think there are bigger things to focus on.”
Sauceda says she’s “never been a huge fan of intermittent fasting” and does not typically recommend it. She adds that there are better ways to optimize nutrition that will have a bigger impact on health.
“For example, many people are not eating the recommended amounts of fiber each day, and that can have a big impact on heart health, your digestion, and blood sugar,” Sauceda says.
Other behaviors that might help you lose weight
Overall, the researchers stressed that rather than following generalized guidelines, dietary recommendations should be more personalized to individuals and their health status.
“I found this study very interesting because I think it emphasizes the point that there’s no ‘one diet fits all’ approach,” Sauceda says.
In fact, Sauceda contends that the weight loss that comes with intermittent fasting might be at least partially due to factors beyond the fasting itself.
“A lot of the times when people try new eating styles and find success, it usually comes from a combination of factors,” she says.
She encourages those who have found success with intermittent fasting to think about other things they may have changed when they adopted the practice of fasting.
For example, ask yourself the following:
She notes that all of these changes can continue to provide benefits to your waistline and overall health even if you drop intermittent fasting due to concerns about its potential impact on heart health.
“In fact, it’s the simplest things that people are more likely to stay consistent with,” Sauceda says, adding that sticking with such easy-to-maintain changes can “have a big impact on their health.”
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