Radical intermittent fasting, calorie-restricted diet extends life in mice. Could it work in humans too?
- Limiting the diets of mice, and restricting feeding to a three-hour daily window, is linked to improved metabolism and a longer life, researchers have found
- If the findings apply to people, those already cutting their daily calorie count by 20 or 30 per cent may want to add intermittent fasting to the mix
Eating less often does more to improve the health and lifespan of rodents than simply eating less, a study said on October 18.
Researchers looking at mice on different diets found those who were fed fewer calories in a single daily feeding lived longer than mice eating the same number of calories distributed throughout the day.
Study author Dudley Lamming of the University of Wisconsin in the US said that scientists have known for about a century that restricting calories extends rodents’ lifespan.
Lamming’s team decided to find out whether the timing between feedings might play a role – and discovered it was not the quantity of food alone that mattered.
“Instead, calorie-restricted diets ensure that mice are fasted for much of the day – and that imposed fasting period [when we eat] is critical for the benefits of calorie restriction to life and health.”
Lamming’s team put mice on different diets, with a control group getting unlimited access to regular food.
Two other groups had calories restricted by 30 per cent, one with access to low-calorie food all day and the other receiving a 30 per cent smaller amount of regular food in a single feeding with a 21-hour fast.
The study shows that mice on a calorie restricted diet with 21 hours between meals lived about half a year longer than mice who ate as much as they wanted at any time of day.
Mice with constant access to a low-calorie diet, on the other hand, lived slightly shorter lives than the control group, even though they consumed fewer calories.
“The imposed fasting period is essential for the benefits of a calorie-restricted diet,” Lamming said.
Though their longevity was not measured, the mice in the last group – which fasted without reducing calorie intake – showed just as many health benefits as the group that ate fewer calories and fasted.
“[Both groups] are better able to regulate their blood sugar and to better adapt their metabolism to different demands during the course of the day,” Lamming said.
Diets that include intermittent fasting are popular among celebrities from Hugh Jackman to Kourtney Kardashian.
But Lamming points out that while short-term studies on humans seem to confirm that restricting food intake to a four- to eight-hour window in the day “seems to have some benefits”, the long-term consequences remain unknown.
“We still don’t know the best time of day to fast, if different people might respond to fasting or time-restricted feeding differently,” he added.
One takeaway for our species: people already cutting their daily calorie count by 20 or 30 per cent may want to consider limiting the time frame for eating those meals.
“If our findings apply to people, they may be losing some of the benefits of calorie restriction by spreading out their meals throughout the day,” he said.