For seven years, Dr. Ethan Weiss, a cardiologist at the University of California, San Francisco, has experimented with intermittent fasting. After a series of promising studies in rats it has been suggested that it may be an effective weight loss strategy in humans.
So Weiss decided to try it, limiting his diet to eight hours a day. After he shed a few pounds, many of his patients asked him if it worked for him.
In 2018, he and a group of researchers began a clinical trial to study it. The results, released on Monday, took him by surprise.
The study found “no evidence” that time-restricted eating serves as a weight loss strategy.
People who were assigned to eat at a random time within a strict eight-hour window each day, skipping meals in the morning, lost an average of 2 pounds over a 12-week period. Subjects who ate at normal meals, with the permission of breakfast, lost 1.5 pounds. The discrepancy was “not statistically significant”, according to the UCSF’s research team.
He said by phone, “I went in this hope to show that I have been doing this for years.” “But as soon as I saw the data, I stopped.”
Some evidence of muscle mass damage
Internal fasting, once the trend among self-styled “biocursors” who use diet and lifestyle tweaks to try and improve their health, has become increasingly mainstream over the past decade. Instagram influencers regularly pay attention to trends, and super-fit celebrities like Hugh Jackman say it helps shape them for movie roles. In Silicon Valley, entrepreneur Kevin Rose launched an app called Rise to get people to keep an eye on their fasts and noted that scientific data is “starting to get very exciting.” Twitter CEO Jack Dorsey and actress Jennifer Aniston are also popular fans.
Too many stars with its advantages, in 2019, intermittent fasting was the top trending diet search in Google, according to Google Trends data.
But scientific evidence in humans is still thin. So the UCSF study, led by DREB TREAT (WRE) and graduate student Derek Law, aims to fill some research gaps with randomized controlled trials.
Starting in 2018, they recruited 116 people who were overweight or obese. All participants received a scale connected via Bluetooth, and were asked to exercise as they normally would.
Weiss suggests that both groups have lost weight due to the placebo effect: Many people will pay more attention to what they eat when enrolled in a nutrition study, meaning they are more likely to make healthy food choices.
So he goes on to say, consumers claiming weight loss benefits should be increasingly skeptical about any nutrition study that does not include the control group.
There may also be potential harm to intermittent fasting. A small percentage of participants were asked by researchers to come to the site for a more advanced test, including fat content, lean mass, fasting glucose, fasting insulin, etc. By that measure, the researchers found that people who were engaged in a time-restricted diet seemed to lose more muscle mass than the control group. Weiss says the result was not determined, but he hopes to continue the study.
Further studies are also needed to show whether intermittent fasting is safe for people over 0 years of age, or for chronic illnesses and medications such as diabetes.
Still, twenty intermittent fasting is not entirely ready to write – there can be benefits around fasting at different times of the day. Participants in Weiss’s study skipped meals in the morning. He had not studied the effects when it came to missing a meal at night.
But for now, he won’t recommend it to his patients.
“Just losing weight doesn’t mean things are going well for your health.”
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