The End of the Day

Suddenly We’re Done with Time-Restricted Eating?

The headlines paint a stark picture. Time-Restricted Eating Doesn’t Work for Weight Loss says the UCSF news story. Based solely on the the conclusions of this one study, we should get over it. Time-restricted eating offers no advantages for weight loss. This new, well-controlled study in JAMA Internal Medicine says so. Suddenly the benefits of a super popular form of intermittent fasting might be another busted myth.

Even worse, it has a downside. In this randomized controlled trial, the people in the time-restricted eating group lost more muscle than those in the control group.

 A Solid Study with Surprising Results

Make no mistake about it, this study is highly credible. It was a 12-week study with 116 adults. Their BMI ranged from 27 to 43. Researchers randomly assigned them to either eat three structured meals a day in the control group or to eat whatever they wanted, but only between noon and eight in the evening. After that, they fasted until noon the next day.

Folks in both groups lost weight, but the weight loss was only significant in the fasting group. They lost about two pounds. Folks in the control group lost one and a half. The difference in weight loss between the two groups was insignificant (p=0.63).

However, researchers found significantly more loss of lean muscle in the fasting group. This was a secondary outcome, so it’s not the final word. But it is a note of caution.

These results surprised the senior author on this study. Ethan Weiss was a fan of time-restricted eating. He told the New York Times:

“My bias was that this works and I’m doing it myself, and so I was shocked by the results.”

Pesky Details

Hold on just a minute, though. Studying dietary behavior is quite complicated because this subject has many moving parts. In particular, the choice of the time window stands out in this study. Courtney Peterson, a researcher on this subject at UAB advises caution before making sweeping conclusions:

“It could be that the benefits of time-restricted eating are smaller than we thought, or that you just get better results when you eat earlier in the day. The jury is still out.”

In fact, there’s reason to believe that eating earlier in the day can help with both metabolic function and weight control. So, indeed, feeding late in the day might give different results from feeding early in the day.

Thus, this very interesting and well-controlled study of time-restricted eating gives us important information. But it’s hardly the final word on time restricted eating or intermittent fasting. We have much yet to learn.

Click here for the study and here for more from the Times. For an excellent thread by Weiss about this study on Twitter, click here.

The End of the Day, painting by Vincent van Gogh / WikiArt

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September 29, 2020