Intermittent fasting, a trendy weight-loss diet favored by some celebrities, does not extend lifespan, a major study suggests.
Instead, eating less overall helped increase lifespan, experts found in a unique study in mice.
But slimmers looking to shorten their love handles beware: it’s crucial not to lose weight in the process, as this could have the opposite effect, according to the results.
In an experiment with 1,000 mice, unrelated mice, American researchers tried to investigate exactly how diets affected lifespan.
The mice were unrelated, rather than the laboratory standard of closely related animals, to better mimic a human population.
Intermittent fasting, a trendy weight-loss diet favored by some celebrities, doesn’t actually extend lifespan, a major study suggests
Rodents were divided into five groups: one with unlimited food all the time, two in which they were fed 60 to 80 percent of their normal food, and two in which mice were fed an unlimited amount of food, but only on one or two days each day. week.
They were then studied for the rest of their lives.
Publish their results in NatureResearchers found that mice on the 60 percent restricted diet lived the longest on average, about 34 months.
In human terms, this is roughly equivalent to someone in their mid-eighties.
Mice on an 80 percent diet then lived the longest, an average of 30 months, which is equivalent to the early 80s in humans.
By comparison, rodents on an intermittent fasting diet lived an average of just 28 months, about the mid-seventies in human terms.
Animals given the freedom to eat as much as they wanted lived the shortest, an average of 25 months, the equivalent of reaching the 1970s for a person.
This result meant that eating fewer calories had a greater impact on lifespan than fasting, and this was true regardless of how fat or fit individual mice were when the results were analyzed on a mouse-by-mouse basis.
And in a discovery that surprised the researchers, it wasn’t weight loss from eating fewer calories that seemed to have this effect.
In fact, it was the mice that lost the least weight despite their severely restricted diets that tended to live the longest in the experiment.
In contrast, those who did lose weight on these diets tended to have low energy levels, weakened immune and reproductive systems, and a shorter lifespan.
Professor Gary Churchill from the Jackson Laboratory in New Jersey said: ‘Our research really points to the importance of resilience.’
He added: ‘The most robust animals maintain their weight even under stress and calorie restriction, and they are the ones that live the longest.’
‘It also suggests that a more moderate level of calorie restriction could be the way to balance health and longevity in the long term.’
However, the researchers said that another crucial part of their study, and why they used genetically diverse mice for the experiment, is that there was enormous variation in lifespan between all groups of mice.
For example, even among the mice on a calorie-restricted diet, individual lifespans ranged from just a few months to four and a half years.
Upon further analysis of the mice, researchers discovered genes that increased resilience, but they helped maintain body weight, body fat percentage and immune cell health during periods of stress that lived the longest.
The experts said this showed that while diet can be used to influence lifespan, an individual’s lifespan may ultimately depend on genes.
Professor Churchill said: ‘If you want to live a long time there are things you can control during your life, such as your diet, but what you really want is a very old grandmother.’
Jennifer Aniston (left) and Nicole Kidman (right) are two starts previously linked to intermittent fasting
From the Kardashians to Prime Minister Rishi Sunak, it seems almost everyone has tried fasting. Proponents say the trend of extreme dieting boosts energy levels and helps lose fat. Some opt for 24-hour fasting, while others cram all their daily meals into a tight six-hour window in an attempt to achieve a range of claimed health benefits. But some research has suggested that skipping meals and delaying breakfast can also increase your risk of diabetes and even lead to a heart attack
This research took place on mice and is therefore of limited applicability to humans.
But Professor Churchill said the results had important implications for research into extending human lifespan, a field that typically looks at how metabolism functioned as a measure of biological age.
“Although calorie restriction is generally good for longevity, our data show that losing weight through calorie restriction is actually bad for longevity,” he said.
“So when we look at human trials of longevity drugs and see that people lose weight and have better metabolic profiles, it turns out that this may not be a good indicator of their future longevity at all.”
Several famous faces have used or reportedly used intermittent fasting over the years.
Actors Mark Wahlberg (left) and Chris Pratt (right) have also used intermittent fasting to slim down for their roles
Benedict Cumberbatch and former Prime Minister Rishi Sunak have also been linked to the diet in the past
Kourtney Kardashian is also among the top performers who have jumped on the fasting trend since it emerged in early 2010. She is pictured here earlier this year
These include Jennifer Aniston, Benedict Cumberbatch, Kourtney Kardashian and Nicole Kidman.
In October 2019, Aniston said she doesn’t eat breakfast and only starts eating after noon.
Mark Wahlberg is also a fan of intermittent fasting, where he doesn’t eat his first meal until noon. He stops eating at 6 p.m.
Actor Chris Pratt also credits intermittent fasting for helping him lose 50 pounds for action star roles.
It’s not just the Hollywood elite, ex-Prime Minister Rishi Sunak also followed the trend, stating in 2022: ‘I do intermittent fasting, so most days I don’t have anything for breakfast.’
However, some studies have found that such diets can increase the risk of diabetes and even lead to a heart attack.