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

Michie · Mar 28, 2024

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:

Continued below.