A Newspaper Seller in Paris

Unrestrained Puffery About Time-Restricted Feeding

“Time-restricted feeding could be key to combat obesity,” says the headline. The press release from the University of California at San Diego is a little more restrained, though. “A rhythmic small intestinal microbiome prevents obesity and type 2 diabetes,” it says. Then finally we get down to reality in the paper. There we find that there’s no combatting of obesity, no prevention of type 2 diabetes in this study. Instead, it’s a study of how diet and feeding patterns affect the microbiome in a portion the small intestines of mice. It’s a fine study that also provides a case study of unrestrained puffery about time-restricted feeding.

Time-Restricted Feeding in Mice

In Cell Reports this week, Ana Carolina Dantas Machado and colleagues published this study of time-restricted feeding in mice. In short, what they showed is that time-restricted feeding can restore diurnal dynamics of the microbiome in mice after a high-fat diet disrupts it. They found it restored a healthy rhythm to the microbiome, better bile acid signaling, and GLP-1 regulation.

These are all good signs for a healthier microbiome. But they don’t really qualify for evidence of overcoming obesity or preventing diabetes, because this is a study of mechanisms in mice. Not clinical outcomes in humans. It adds to our knowledge about the effects of time-restricted feeding. But it tells us nothing about how effective it might be for treating or preventing obesity or diabetes.

Fuel for Faddish Fasting Fashions

This is hardly the first and won’t be the last of puffery about time-restricted feeding. The rhythm of time is essentially linked to the healthy function of our bodies. We have a lot to learn about it and many smart scientists are pursuing that knowledge. That’s all good.

But less good is the fuel that this puffery gives to faddish intermittent fasting advice. It’s also not very helpful when people suggest (as they did last week in BMJ Nutrition, Prevention & Health) that intermittent fasting might protect us from COVID like a vaccine does. That was based upon an observational study of 205 people who tested positive for COVID. It’s far from being evidence of effectiveness. Rather, it’s a convenient observation of an association.

When it comes to intermittent fasting, though, it seems like people are eager to jump on fragments of evidence and leap to some pretty bold conclusions right now. Take it all with a grain of salt.

Click here for the study of time-restricted feeding that sparked all this puffery. For a deeper dive into the intense research interest in circadian medicine, click here.

A Newspaper Seller in Paris, painting by Ilya Repin / WikiArt

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July 7, 2022