Restricting eating to six to eight hours a day does not lead to faster weight loss, according to a study.
Hollywood A-listers including Jennifer Aniston and Nicole Kidman both reportedly used intermittent fasting to lose weight.
But Chinese researchers now say the strategy – which became popular in the 2010s – is no more effective than restricting a person’s calorie intake.
dr Ethan Weiss, a nutrition researcher at California University in San Francisco, told the New York Times that there is “no advantage to eating in a tight window of time.”
He said only “calorie restriction” can help people lose weight.
Jennifer Aniston (right) and Nicole Kidman (left) are two celebrities who are also said to have used intermittent fasting
What is intermittent fasting?
Intermittent fasting involves alternating days of fasting with days of eating normally.
Intermittent fasting diets generally fall into two categories – time-restricted diets that limit meal times to 6-8 hours a day, also known as the 16:8 diet, and 5:2 intermittent fasting.
The 16:8 diet is a form of intermittent fasting, also known as time restricted eating.
Adherents to the diet fast for 16 hours a day and eat whatever they want for the remaining eight hours — typically between 10 a.m. and 6 p.m.
This may be more tolerable than the well-known 5:2 diet, in which adherents limit their calories to 500 to 600 a day two days a week and then eat normally for the remaining five days.
In addition to weight loss, 16:8 intermittent fasting is said to improve blood sugar control, boost brain function, and help us live longer.
Many prefer to eat between noon and 8 p.m. as this means they only have to fast overnight and skip breakfast, but can still eat lunch and dinner along with some snacks.
When you eat out, it’s best to opt for healthy options like fruits, vegetables, and whole grains.
And drink water and unsweetened beverages.
Disadvantages of the fasting plan can be that people exaggerate the hours they can eat, leading to weight gain.
It can also lead to long-term digestive problems, as well as hunger, fatigue, and weakness.
In the study, published in the New England Journal of Medicine, scientists at Southern Medical University in Guangzhou, China, followed 139 obese people for a year.
They were divided into two groups, with some being placed on a calorie-restricted diet that allowed them to only eat between 8am and 4pm each day.
The others received the same calorie restrictions but were allowed to eat at any time.
Women in the study could eat between 1,200 and 1,500 calories per day, while men could consume 1,500 to 1,800 per day. This is about a quarter below the recommended daily allowance for both groups.
To ensure participants were sticking to the plan, they were asked to photograph everything they ate and to keep a food diary.
The results showed that people in the time-limited group lost 18 pounds over the year, while those in the other group lost 14 pounds.
But there was no significant difference between the results, meaning the different eating plans didn’t trigger the differences in weight loss.
There was also no significant difference between the two in waist circumference, body fat, or lean body mass.
“A time-restricted eating regimen was no more beneficial in terms of reducing body weight… than daily calorie restriction,” the researchers wrote in the paper.
“These results suggest that caloric restriction explains most of the beneficial effects observed with time-restricted diets,” Weiss said.
Trending fasting diets have been popular since the 2010s and have been adopted by various celebrities such as Jennifer Aniston, Reese Witherspoon and Twitter CEO Jack Dorsey and Benedict Cumberbatch.
In October 2019, Jennifer Aniston said she doesn’t eat breakfast and only drinks liquids in the morning, saving herself from eating until the latter half of the day.
Actor Benedict Cumberbatch is also said to have used the 5:2 intermittent fasting method to shed the pounds as the title character in the BBC drama Sherlock.
However, several studies now suggest that intermittent fasting does not lead to faster weight loss.
In an article published in JAMA Internal Medicine in 2020, 116 participants were asked to eat three meals a day whenever they wanted, or between 12 p.m. and 8 p.m., over a 12-week period.
The results showed that participants in both groups lost between 1.5 and 2 pounds, with no significant difference between the two.
However, other scientists have praised the method’s benefits, saying it can help prevent heart disease and type 2 diabetes.
Professor Satchidananda Panda of the Salk Institute for Biological Sciences in California wrote last year in the journal Endocrine Reviews: “People trying to lose weight and lead a healthier lifestyle should pay more attention to when they eat and what they eat.
“Time restricted eating is an easy-to-follow and effective nutrition strategy that requires less mental arithmetic than counting calories.
“Intermittent fasting can improve a person’s sleep and quality of life, as well as reduce their risk of obesity, diabetes and heart disease.”
Professor Panda said that failure to respect the body’s internal clock, also called the circadian rhythm, could harm people’s health because the body’s genes are activated at different times of the day and hormone levels and metabolism vary within 24 hours.