Hopefully this will work for humans
Howard
Hughes Medical Institute
Now,
new research suggests that the body's daily rhythms play a big part in this
longevity effect. Eating only during their most active time of day
substantially extended the lifespan of mice on a reduced-calorie diet, Howard
Hughes Medical Institute Investigator Joseph Takahashi and colleagues report
May 5, 2022, in the journal Science.
In
his team's study of hundreds of mice over four years, a reduced-calorie diet
alone extended the animals' lives by 10 percent. But feeding mice the diet only
at nighttime, when mice are most active, extended life by 35 percent. That
combo -- a reduced-calorie diet plus a nighttime eating schedule -- tacked on
an extra nine months to the animals' typical two-year median lifespan. For
people, an analogous plan would restrict eating to daytime hours.
The research helps disentangle the controversy around diet plans that emphasize eating only at certain times of day, says Takahashi, a molecular biologist at the University of Texas Southwestern Medical Center. Such plans may not speed weight loss in humans, as a recent study in the New England Journal of Medicine reported, but they could prompt health benefits that add up to a longer lifespan.
Takahashi's
team's findings highlight the crucial role of metabolism in aging, says Sai
Krupa Das, a nutrition scientist at the Jean Mayer USDA Human Nutrition
Research Center on Aging who was not involved with the work. "This is a
very promising and landmark study," she says.
Fountain
of youth
Decades
of research has found that calorie restriction extends the lifespan of animals
ranging from worms and flies to mice, rats, and primates. Those experiments
report weight loss, improved glucose regulation, lower blood pressure, and
reduced inflammation.
Butit
has been difficult to systematically study calorie restriction in people, who
can't live in a laboratory and eat measured food portions for their entire
lives, Das says. She was part of the research team that conducted the first
controlled study of calorie restriction in humans, called the Comprehensive
Assessment of Long-term Effects of Reducing Intake of Energy, or CALERIE. In
that study, even a modest reduction in calories "was remarkably
beneficial" for reducing signs of aging, Das says.
Scientists
are just beginning to understand how calorie restriction slows aging at the
cellular and genetic level. As an animal ages, genes linked to inflammation
tend to become more active, while genes that help regulate metabolism become
less active. Takahashi's new study found that calorie restriction, especially
when timed to the mice's active period at night, helped offset these genetic
changes as mice aged.
Question
of time
Recent
years have seen the rise of many popular diet plans that focus on what's known
as intermittent fasting, such as fasting on alternate days or eating only
during a period of six to eight hours per day. To unravel the effects of
calories, fasting, and daily, or circadian, rhythms on longevity, Takahashi's
team undertook an extensive four-year experiment. The team housed hundreds of
mice with automated feeders to control when and how much each mouse ate for its
entire lifespan.
Some
of the mice could eat as much as they wanted, while others had their calories
restricted by 30 to 40 percent. And those on calorie-restricted diets ate on
different schedules. Mice fed the low-calorie diet at night, over either a
two-hour or 12-hour period, lived the longest, the team discovered.
The
results suggest that time-restricted eating has positive effects on the body,
even if it doesn't promote weight loss, as the New England Journal of
Medicine study suggested. Takahashi points out that his study likewise
found no differences in body weight among mice on different eating schedules --
"however, we found profound differences in lifespan," he says.
Rafael
de Cabo, a gerontology researcher at the National Institute on Aging in
Baltimore says that the Science paper "is a very elegant
demonstration that even if you are restricting your calories but you are not
[eating at the right times], you do not get the full benefits of caloric
restriction."
Takahashi
hopes that learning how calorie restriction affects the body's internal clocks
as we age will help scientists find new ways to extend the healthy lifespan of
humans. That could come through calorie-restricted diets, or through drugs that
mimic those diets' effects.
In
the meantime, Takahashi is taking a lesson from his mice - he restricts his own
eating to a 12-hour period. But, he says, "if we find a drug that can
boost your clock, we can then test that in the laboratory and see if that
extends lifespan."
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