835. A new study suggests that a short eating window more than doubles your risk of dying from cardiovascular disease. But is that really what the data shows?
835. A new study suggests that a short eating window more than doubles your risk of dying from cardiovascular disease. But is that really what the data shows?
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A new study claims that eating in an 8-hour window each day could more than double your risk of dying from heart disease. That’s a headline designed to stop you in your tracks—especially if you’ve been experimenting with intermittent fasting. But what does this study really show, and should it change the way you eat?
Hello! I’m Monica Reinagel and you are listening to the Nutrition Diva podcast, a show where we take a closer look at nutrition news, research, and trends so that you can make more informed decisions about what (and when!) you eat.
A recent study on intermittent fasting has been getting a lot of attention. The fasting technique known as TRE (time-restricted eating)—basically, restricting all your food intake to a relatively short window of time each day–remains very popular with both researchers and the general public as a tool for weight loss and weight maintenance, but also as a strategy for managing blood sugar, slowing the aging process, and more.
And this new analysis has thrown some cold water on all of that enthusiasm. It found that people who observed an eight-hour eating window each day had a significantly higher risk of dying from cardiovascular disease. I’ve already heard from several listeners, asking for my thoughts on this new finding. So, let’s take a closer look at what this new study actually found and what this might mean for you, if you are someone who has adopted (or is thinking about trying) this approach.
The researchers looked at about 20,000 American adults and divided them into groups according to how long their reported eating window was–that is, the time between their first and last meals of the day. And they found that those who reported a very short eating window (less than 8 hours between their first and last bites) were more than twice as likely to die of cardiovascular disease as those with a longer eating window (12 hours or more).
That’s the headline. And, as headlines go, it’s a good one, in that it’s pretty sensational. If you are someone who practices or recommends this style of intermittent fasting, it probably got your attention. But I think there are some important caveats that need to be considered before we over-react.
First off, this is obviously a correlation. It does not prove that the length of the eating window had anything to do with these people’s cause of death. In fact, another detail from the study bears mentioning: Although this analysis found that the people with the shortest eating window had a higher risk of death from heart disease, they did not have a higher risk of dying overall. That would seem to imply that even if they had an increased risk of CVD, they must have had a lower risk of dying of any other causes, such as cancer.
More likely, this paradox is explained by the various kinds of uncertainty that can be introduced in these types of statistical analyses. For example, if there were relatively few deaths from CVD in this group, then a small increase could have had an outsize effect on the risk calculations. For you statistics nerds out there, the CI (or confidence interval) for this finding was 1.39–3.98, suggesting that there’s a lot of wiggle room here.
But I don’t think you need to be a statistics nerd to appreciate some of the other limitations in this analysis.
This study was done using data from a large ongoing U.S. survey called NHANES. Part of this survey involves participants doing something called a 24-hour dietary recall. Working with a trained interviewer, the participants report everything they ate or drank over a 24-hour period and this information gets tabulated and entered into the database. This allows researchers to look at associations between intake of various nutrients and food groups (or, in this case, the length of various eating windows) with different health outcomes.
Participants typically do a couple of those recalls over the course of a study, in an effort to capture what their typical eating patterns are. But I want you to just pause for a moment and think about your own eating patterns. How much do they change from day to day or season to season? How likely is it that a recall you did on a random day 5 years ago reflects how you typically eat today?
Over the past ten years or so, have you ever adjusted the composition of your meals in response to new research or information? I know I have. Or perhaps you’ve made modifications because of changes in your health or lifestyle? Have you ever tried out a new eating pattern or dietary approach for a few days or weeks and then decided it wasn’t for you? I sure have.
If I were to throw a dart at the calendar and do a 24-hour dietary recall with you, what are the chances that that day would be representative of your typical eating patterns over the course of that entire year…much less that entire decade?
My point is this: Even if we assume that people accurately remember and report everything that they eat (which is a big assumption), I still have my doubts that these 24-hour recalls give us a reliable picture of people’s eating windows over time. Or that these outcomes necessarily apply to people who are intentionally following a time restricted eating protocol.
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When I saw the headlines regarding this newly published paper, I had a moment of déjà vu, because I remembered similar headlines popping up about a year and a half ago.
That’s because this isn’t the first time we’ve seen results from this research group. Back in March of 2024, they presented preliminary findings at a meeting of the American Heart Association. At that time, the data suggested that people who reported a shorter eating window had a 91% higher risk of dying from cardiovascular disease, compared to those who spread their intake out over a wider time frame. Not quite as dramatic as the 135% increase in risk in the final paper, but still enough to garner media attention.
But it also drew some constructive criticism from experts. For example, Dr. Kevin McConway, an Emeritus Professor of Applied Statistics at Open University, had this to say: “To relate their eating times over those two 24-hour periods to a deliberate long-term time-restricted eating intervention seems to be going far beyond the data.”
Tom Sanders, a Professor emeritus of Nutrition and Dietetics at King’s College London pointed out that the people reporting short eating windows may be doing so because they work jobs that hinder their ability to have more regular meal times, things like truck drivers, security personnel, health professionals, night workers…types of work that are known to be associated with increased risk of type 2 diabetes and CVD.
Others pointed out that people who were already sick might have been more likely to eat in shorter windows—what researchers call reverse causation—and that this could explain the association.
And this is exactly how this works: Preliminary findings get aired at conferences, where other scientists can poke holes, raise questions, and suggest refinements. The authors then go back, take that feedback into account, and—ideally—produce a stronger, more carefully analyzed paper.
That appears to be what happened here. The subsequent publication actually sharpened the conclusion: Instead of a 91% higher risk, the refined analysis now reports a 135% higher risk of cardiovascular mortality for those with shorter eating windows. (They accomplished this by dividing the subjects into narrower eating window buckets.)
But what it didn’t do is erase the baked-in limitations of the study design. At the end of the day, although the size and scope of the NHANES dataset make it an attractive target for researchers, it’s probably not the best tool for answering this particular study question.
So what does all of this mean for you?
First, there’s no reason to panic if you’ve been experimenting with intermittent fasting or time-restricted eating. This study does not prove that eating within a short window causes cardiovascular disease.
If you find that limiting your eating to a window helps you manage your appetite, your weight, or your blood sugar, there may be real benefits to this approach. But those benefits don’t require you to compress everything into a strict 8-hour span. A more moderate eating window — say, 10 to 12 hours a day — may provide the same advantages while avoiding the concerns flagged in this research.
And remember: meal timing is just one piece of the puzzle. The quality of the food you eat, how active you are, how well you sleep, and how you manage stress probably have a much larger impact on your risk of heart disease and overall health than whether you finish your dinner at 3 p.m. or 6 p.m.
Finally, if you have an existing condition like cardiovascular disease, diabetes, or cancer, it’s always smart to talk with your doctor or a nutrition professional before adopting an extreme eating window or any other big change in your diet. They can help you weigh the potential risks and benefits in the context of your overall health.
Meanwhile, If you have another question you’d like me to tackle on the podcast, you can email me at nutrition@quickanddirtytips.com. And if you are an educator or health professional, these are the types of topics that I regularly present on in educational settings and at professional meetings throughout the country. For more information, please check out wellnessworkshere.com
Nutrition Diva is a Quick and Dirty Tips podcast. Holly Hutchings is our Director of Podcasts. Steve Riekeberg is our audio engineer, Morgan Christianson heads up Podcast Operations & Advertising, and Rebekah Sebastian, is our Manager of Marketing and Publicity and Nat Hoopes is our Marketing and Operations Assistant. Thanks to all of them and thanks to you for listening!