That New Intermittent-Fasting-Is-Deadly Study Is Not So Hot

That New Intermittent-Fasting-Is-Deadly Study Is Not So Hot

This post will also run at the Broken Science Initiative site later today.

A new study came out that claimed intermittent fasting is bad for you. This shocked a lot of people. Here’s one of the hot headlines: “8-hour time-restricted eating linked to a 91% higher risk of cardiovascular death“.

Ninety one percent? Dude. That’s a lot. Makes it sounds like skipping a meal could kill you.

Intermittent fasting is the idea you group your daily meals into some short period of time, typically something like over eight hours or less. Many have found this to produce a range of health benefits, including Yours Truly. At the least it inculcates discipline, a virtue sorely needed in our culture.

Here are the “research highlights” from the press release:

  • A study of over 20,000 adults found that those who followed an 8-hour time-restricted eating schedule, a type of intermittent fasting, had a 91% higher risk of death from cardiovascular disease.
  • People with heart disease or cancer also had an increased risk of cardiovascular death.
  • Compared with a standard schedule of eating across 12-16 hours per day, limiting food intake to less than 8 hours per day was not associated with living longer.

This research was presented at a meeting of American Heart Association as a poster, which is online here. It’s all we have to go on, since there is not (at this time of writing, anyway) a paper to accompany it.

The authors looked back at data collected in the National Health and Nutrition Examination Surveys (NHANES) study, which ran from 2003 to 2019. It was not an experiment to test intermittent fasting.

NHANES relied on self-reported diet questions. Like the time spacing between meals. Those who reported eating meals over periods of less than eight hours a day likely did not fast each and every day. After all, sometimes that cupcake looks too appealing. So there is some substantial uncertainty here.

That, plus people’s memories are not always reliable about what and when they ate. Indeed, they are notoriously unreliable with their reporting.

Do the authors of the poster “Association of 8-Hour Time-Restricted Eating with All-Cause and Cause-Specific Mortality” account for these great uncertainties? If they did, they didn’t tell us. And likely they did not. Most researchers don’t.

The authors broke up the self-reported times of daily meals into five buckets: less than 8 hours, between 8 and 10, between 10 and 12, between 12 and 16, and greater than 16 hours (essentially eating all day long). They called the 12 to 16 hour bucket the reference group, and calculated statistics with respect to that. The less than 8 hour group is the one that generated the hot headlines.

Here’s a table of the baseline characteristics of the buckets, which reveals something interesting:

First, the eight-hour group was the smallest, so it would have the greatest uncertainty.

Second, and more interesting, it had by far the most blacks at 23.3%; whereas the reference group (12-16 hours) only had 6.6%. This is important because blacks suffer from cardiovascular diseases at rates much greater than whites. One prominent source says “47% of Black adults have been diagnosed with cardiovascular disease, compared with 36% of white adults.”

Which means the obvious: that the racial imbalance of the time buckets could account for the headline-generating results.

Adding weight (ahem) to this possibility is that the 8 hour group had the highest average BMI: 29.9 vs the 28.5 in the reference group. The fatter you are, the greater the chance for cardiovascular disease (CVD).

Lastly, there were more smokers in the 8 hour group: 27.1% vs 16.9%. Another whopping difference.

The authors used a type of regression called Cox proportional hazards. They say they “control” for things like age, race, smoking, and BMI. But that word doesn’t mean what you think it means; it is one of several unfortunate words (like “significance”) that litter statistics and give the false impression certainty is greater than it is.

Here, “control” says the authors included these measures in the model along with time groups. It is not anything like real control, a key weakness of regressions that most forget. The racial and other imbalances of the sample can’t be wholly fixed by this kind of “control.”

Finally, the results.

There were no differences in all-cause mortality, in the regressions, between any of the time groups. Meaning the people in the intermittent fasting 8 hour group did not die at faster rates. Same for deaths in those people who already had CVD or cancer. No real differences. We don’t know what the raw counts were: we just see model output.

The same no signal was found for cancer mortality. No real differences in deaths for any time group.

The only signal in the model was for cardiovascular deaths. There, people in the 8-hour group had slightly—and it was only very slightly—larger hazard ratios than the reference group.

Does this mean the 8-hour group had worse outcomes because of fasting? Maybe. But the differences could just as easily be due to race, fatness, and smoking. And they almost certainly are, given the numbers we’ve seen. Especially since we haven’t even considered how self-report plays into this.

The press release included this gem:

“We were surprised to find that people who followed an 8-hour, time-restricted eating schedule were more likely to die from cardiovascular disease. 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,” Zhong said.

His findings went smack against massive contrary evidence, which surprised him. But not enough for him to question the modeling techniques he used.

Yet again, classical statistical procedures generate more certainty than is warranted.

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  1. Phoenix

    Lost 150lbs. over six years after a stroke by fasting/exercising and using the all time best diet ever known as eat less move often.
    If I start to feel weak or wobbly during fast then it is over and a meal is prepared.
    The longest I have went is about 2 days.

  2. Gunther Heinz

    This is how it works. People who click on intermittent fasting links also click on right-wing content. Accordingly, intermittent fasting MUST be bad. Science!

  3. Sid Porter

    Holy smokes! Don’t sleep in or you might wake up dead!

  4. Incitadus

    This is just another one of those studies like eggs, meat, butter, whole milk, cheese, or any type of fat
    is bad for you. The brainwashing has been continuous since the introduction of margarine in 1912
    with paid for endorsements by the American Heart Association resulting in skyrocketing heart disease.
    Could there possibly be a connection with ill health and profits? The America public has been bombarded
    non-stop with this sort of messaging only to have grown fatter, sicker, more depressed and uncertain over
    the years. Now we are being treated to upside down world were there is not even a pretense of common
    sense or reason entering the onslaught of lies and half truths vomited up daily in the corporate press.

    Bit dated but relevant as ever:
    The Oiling of America

  5. Cary D Cotterman

    No matter what you eat, or don’t eat; no matter when you eat it, or don’t eat it; no matter how much of it you eat, or don’t eat, there’s an expert to tell you it’s good, and another expert to tell you it’s bad. Any more, I just eat the way it works for me to be fit and not get fat. Close enough.

  6. Johnno

    Were any or all 20,000 adult participants in the study at any time required to be vexxinated?

    Will every study now be contaminated due to the pool of the vexxine approved?

    Were the Expurts forbidden to notice?

  7. > Which means the obvious: that the racial imbalance of the time buckets could account for the headline-generating results.

    This study has “low socioeconomic status is bad for your health” written all over it. Poor people have to work two jobs so they don’t have the time to eat, hence only one meal per day – intermittent fasting. They smoke. They drink. They do drugs. They don’t get enough sleep. And so they die younger. They’re also more commonly black but that probably doesn’t have an effect on their health or longevity. Living a shit life – that’s what kills you. Being black is just correlated to it.

  8. Hagfish Bagpipe

    That’s quite a write up, Briggs. How do you find time for these daily writers’ struggle sessions? I’m picturing you like some 1930s crime reporter for the Gotham sun, late night desk, dim pool light gooseneck lamp, bakelite phone, brain over-heated, jacket off, tie askew, fedora dented, smoking ashtray full, machine gun remington typewriter, fingers frazzled. That kind of thing. Fleet-footed fencer of fools, magick unveiled, sleight of hand, tophat rabbit, girl sawn in half, Aquinas on shortwave, signals signifier, sartorial snob, and the last bloodthirsty survivor of Roark’s Drift. Sound the Trumpets!

    That’s a pretty good show, Boss.

  9. Hagfish Bagpipe

    Briggs, I have an idea for a piece of my own to write up, title, “The Destructive Principle”, but I’m too much of a lazy, ill disciplined, flackleschluber to actually sit down and write it up, a task I find laborious. Of course, the problem of the world is simply laziness. If we just shot all the lazy people life would be great! I mean, except for me. And Briggs. Briggs might be a fool, but he’s not lazy. I find it hard to write one piece and Briggs pounds out five a week. The man’s a lunatic.

  10. C-Marie

    Thank you, Matt!!
    God bless, C-Marie

  11. Briggs






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