Intermittent fasting is making big waves in the wellness world again, but not with great news.
The American Heart Association this week published results of a study that found that people who restricted their eating to fewer than 8 hours per day have a 91% increased risk of dying from cardiovascular disease compared to people who stretch out their eating hours.
The results of the survey, which included information from more than 20,000 US adults (414 in the 8-hour eating window group) were presented at the Epidemiology and Prevention, Lifestyle and Cardiometabolic Health conference in Chicago. The study hasn't yet been peer-reviewed.
There are different types of intermittent fasting; time-restricted eating, which the latest study focused on, is one of them. People may restrict their eating windows from 12 hours down to 6 or fewer, but an 8-hour eating window is common. Intermittent fasting has gained popularity as a potential way to lose weight, lower cholesterol and reduce other risk factors for heart disease. This is one reason headlines on the recent study were so jarring; previous research had suggested an opposite link to heart health, but with shorter-term results.
But the experts we spoke with urged us not to take the results of this study as a rule; the senior author of the study also stressed in the AHA post that the association found in this study doesn't mean intermittent fasting caused cardiovascular death.
For one, the latest research does not account for the reasons people were restricting their eating window in the first place, or other things that may influence their health. These types of "confounding" factors in health make studies on diets, or wellness in general, tricky, according to Dr. Andrew Freeman, a cardiologist with National Jewish Health in Denver.
"People seldom do harmful or even helpful things in isolation," Freeman said.
People may go for longer periods of time without eating for a variety of reasons, including an erratic work schedule where they may have to get all their food in during a shorter window, they may have disordered eating patterns, they could have a mental health challenge that affects their sleep-wake cycle, and so many more scenarios that would cause someone to report shorter eating windows, but also introduce other factors known to negatively affect cardiovascular health.
Sometimes, people fast for spiritual reasons. Coincidentally, the latest research about time-restricted eating falls as people around the world are observing Ramadan, a holy month of fasting in the Muslim faith.
We may say, then, that the latest research is a catalyst for another conversation on how to find a nutrition plan that works for you and your life, how to tune into your hunger signals and how to practice the best diet for heart health.
What we previously knew about intermittent fasting
Previous research on intermittent fasting has linked it to weight loss, insulin sensitivity (the body's ability to use glucose more efficiently) and more metabolic factors that reflect how our body uses energy and how our health may be affected. It's also been linked to changes in gene expression and longevity.
Weighing the latest research with more positive findings on intermittent fasting or time-restricted eating, Freeman said the diet is an "interesting thing that needs really deep investigation."
"With intermittent fasting, it gives people a chance to cut out calories they would otherwise consume without really realizing it," he said. But, he added, "there's not a lot of solid data that says it's the most amazing thing."
Also, restricting our eating time isn't even that novel of a concept when you consider earlier that the humans we evolved from went longer amounts of time without eating, back before food was "readily available literally everywhere you went," Freeman said.
Krista Scott-Dixon, a health coach and product director of Simple, a nutrition and diet app, stressed that intermittent fasting is "an option, not the only way" to achieve your health goals or weight loss.
"It's not magic," Scott-Dixon said. But for some people, she said, experimenting with restricting eating hours even a little bit can help "reboot hunger and fullness cues," plus help people trust their own bodies.
It can also help people align their circadian rhythms, she said, and is overall a "clearer" approach to dieting, which can feel restrictive, stressful and flat-out ineffective for many people.
There's not one set way to do intermittent fasting or time-restricted eating. Daily restricted eating of an 8-hour window with 16 hours of fasting is one popular way, but not the only way. You may experiment with a 12-hour eating window and 12-hour fasting window, for example. Another fasting method is to eat "normally" for five days a weekand more restrictively for two (These two days shouldn't be consecutive.)
How to safely experiment with intermittent fasting safely (and who should avoid it)
Purposefully going stretches of time without eating isnot safe for everyone. People with diabetes, people who are pregnant or breastfeeding, older adults, children and teens, people taking certain medications and those with a history of eating disorders or disordered eating are just some groups who should avoid intermittent fasting or time-restricted diets. There is also some research that haslinked intermittent fasting to disordered eating and compulsive behavior.
You should always discuss planned changes to your daily diet with a health care provider who knows your full health history.
If you're interested in taking just a bit of time off your eating window, or dipping your toe into intermittent fasting, an easy way to start may be to cater to your natural appetite. Personally, I have more of an appetite later in the day and at night -- I never miss dinner, and I like late-night snacks. On the other hand, I'm usually not hungry in the morning, so I naturally wait a bit most days to eat. (I drink water and coffee during this time.)
So, following my own natural hunger cues, if I were to restrict my eating window, it would probably make more sense for me to take a little bit more time off my eating window earlier in the day, instead of at night when I'm always up and hungry. If you love breakfast and are hungrier earlier in the day, you'd probably benefit from doing the opposite. (When we're hungriest could be influenced by different things, but one of them is the natural difference from person-to-person in sleep chronotypes, or the sleep-wake cycle.) But, as always, talk to a doctor, dietitian or nutritionist about the best window for you.
It's also important to note here that intermittent fasting does not negate the crucial benefits of nutrient-dense foods. If you're only eating foods that don't have much nutritional value in your eating window, and not continuing to prioritize colorful, filling foods, you'll miss out on known heart-health benefits.
What you eat matters: Finding the 'best' diet for heart health
Contrary to what some may think about time-restricted eating or intermittent fasting, what you choose to eatdoes matter, even if you're choosing to follow a time-restricted schedule, or do it less often. While the wellness benefits and risks of intermittent fasting may need more research, makingnutrient-dense foods a priorityis a tried-and-true way to improve your overall health.
"I recommend that people follow the evidence," Freeman said. Evidence has continued to pile up health benefits around a few of the same themes of eating, no matter the region or trend it's named after: a predominantly plant-based diet low in added sugars, preservatives, salts and fats.
However you create your heart-healthy plate is up to you, but popular diets to follow that allow for delicious healthy fats, colorful foods and "less healthy" stuff in moderation include the Mediterranean diet and the Atlantic diet.
Ultimately, the best diet will be whatever feels best for you and what you can continue to do, Scott-Dixon said.
"If you can only do this diet for a week, it's no good for you," Scott-Dixon said.
"It's really about a pattern of behaviors," she added about achieving better health. "I think that's a key piece to understand."
Contrary to popular belief, it shouldn't feel like a chore or stressful to follow a diet. Food is meant to be enjoyed, after all, and your nutrition plan should feel good to you.
