New Study About 16/8 Intermittent Fasting
A study recently published compared weight loss between people following 16/8 intermittent fast and people eating three meals per day. What did we learn!
16/8 Intermittent fasting is one of the most popular time-restricted options. There are overall numerous claims of weight loss and increased energy with fasting. About a year ago, the New England Journal of Medicine published a review article that put intermittent fasting in a positive light, even as a longevity intervention. You can read my article on three things that help longevity here.
A recent study published in JAMA has given us some food for thought. Is it worth doing a 16:8 intermittent fast? I will briefly go through the study first and then discuss the main limitations and our take-home messages.
Study structure
Researchers divided people into two groups:
1) Those that observed 16/8 fast. This group was instructed not to eat anything from 8 pm to noon. They had no limitations or restrictions in the 8 hours from noon to 8 pm.
2) The second group ate three structured meals every day. They were even allowed to eat snacks.
The study included 141 men and women aged 18 to 64 years with a body mass index of 27 to 43. Participants received a Bluetooth scale. The participants were notified daily to check their weight before eating or drinking anything. None of the participants were asked to control calories or other dietary components such as carbohydrates, sugar.
Results
The study found no statistically significant difference in weight loss between the two groups. Both groups lost 1.5–2 lbs in 12 weeks. The authors suggested that 16/8 intermittent fast by itself was not enough for weight loss.
Limitations of the study
First, the participants self-reported. That means there was no supervised way to check if a person followed the 16:8 eating window.
Second, there was no reporting of what the participants ate. Was the group that ate three meals a day just healthier in their food choices overall?
Take-home points
Intermittent fasting gained popularity after experiments in mice showed that mice that were allowed to eat in a restricted window of time lost more weight and did metabolically better. But humans and mice are metabolically very different. A 16:8 fast in mice is nowhere equivalent to a 16:8 fast in humans. For comparable results, humans likely have to fast for days.
The time-restricted window needs to be narrower similar to 20:4 (1 meal a day) if we want to see a more drastic difference in weight loss. During the 16:8 fast, we have ample time to destroy all the work we have done fasting. But a four-hour window will limit the actual amount of food we could take.
This study brings up the importance of quality and food quantity. If we want to do 16:8 fast, it has to be accompanied by one more step: calorie restriction or dietary restriction (like low carb).
Fasting in animal studies has been shown to prolong life. And as reviewed in an article in NEJM, fasting can affect the cellular level to increase cellular resistance to stress and improve longevity. So, is it entirely worthless for attempt 16:8? NO! The participants still lost weight, even if it was a minuscule amount. Time restriction is at least one arm that leads us not to graze all day without any thought. Also, fasting can induce health benefits that can have long term effects.
So, continue the fasting but add one of these:
- narrower eating window
- restricting calories
- adding a dietary restriction
Originally published at https://saritakhemani.com on January 29, 2021.
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