There’s new evidence that shows even more conclusively that a certain diet could slow aging

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There’s long been good reason to think that
some form of calorie restriction could slow aging.

But it’s always been really hard to know whether that strategy
would work for humans.

However, a new study published this week helps clear up some
long-standing confusion about whether restricting calories helps
rhesus monkeys live longer — and the researchers write that they
think their work shows it’s “highly likely” humans could
experience the same benefits for a longer life.

Previously,
scientists have shown that in animals like mice, fruit flies,
rats, certain worms, and yeast, cutting calories a significant
amount (around
30% in one recent mouse study) could extend life and health,
including brain health, for a significant span — sometimes
doubling or tripling it.

But humans are pretty different from these creatures, and often
something that works for a mouse or a fly doesn’t end up working
in a person.

In primates like monkeys, much more closely related to us, the
evidence for calorie restriction (CR) has been more conflicted.
At least one major
study out of the University of Wisconsin (UW) has shown that
monkeys fed restricted diets live significantly longer; but
another major study from the National Institute on Aging (NIA)
indicated
that calorie restricted monkeys weren’t likely to live any
longer, though they still seemed healthier overall.

A
rhesus macaque.

Flickr/Ssppeeeeddy

The effects of diet, sex, and age

The new research, conducted by scientists from UW and NIA and
published
in the journal Nature Communications, helps explain and
resolve these differences.

The study, which analyzes the data from the monkeys at both UW
and NIA, argues that when you take into account certain
differences in the ways the studies were conducted, their
findings aren’t in conflict. Calorie restriction does indeed help
monkeys live longer and healthier, according to the authors. But
there are certain specifics about diet, sex, and the age at which
the process begins that are key for making that dietary
intervention work.

In the original studies, even the monkeys allowed to eat “ad
libitum,” as much as they wanted, ate less and were given
healthier food at the NIA location. At NIA, they began
restricting calories earlier in they monkeys’ lives, since that
worked for mice. It turns out those differences had a big effect.

The more unhealthy processed food that monkeys ate, like those at
UW, the more it shortened their lives. And it turns out that
young monkeys, unlike young mice, are not healthier if their
diets are restricted. Calorie restriction only extended life when
that intervention didn’t begin until the monkeys were adults.

And since monkeys age in similar ways to humans, suffering from
many of the same diseases as they get older, researchers think
this information is relevant for us. The effect of processed
foods on lifespan indicates that even a small shift in diet could
be the difference between a longer, healthier life and a shorter
one. The fact that this intervention only works in adult or older
monkeys shows how these sorts of interventions need to be
developed differently for primates, including people, than they
do for mice. Young monkeys, like young people, need a good amount
of healthy food.

Interestingly, the researchers also found that it’s particularly
bad for male monkeys to eat whatever they want and gain too much
body fat, something that may be relevant for humans as well.

Al
Bello/Getty Images

What about people?

The key finding of this new research, according to the study
authors, is that we seem to be able to change the biological
“fact” that primates become more susceptible to disease as they
get older. And they say that research indications so far seem to
show that humans respond to calorie restriction in ways that are
similar to rhesus macaques.

But that doesn’t mean things are totally settled. This still
hasn’t been shown to work for people, and it’s possible that
humans might not live longer and healthier lives if they eat less
than normal as they grow old.

“My own guess would be that CR is beneficial for some individuals
but not for others,”
Joao Pedro De Magalhaes, a researcher who studies aging and
senior lecturer at the University of Liverpool told me several
months ago. “If you don’t have a healthy diet then CR will likely
help, but so will other less extreme diets … That said, there
are very few studies in humans, so again, this is guesswork.”

And the thing is, even if this does work in humans, how many
people would really want to cut their caloric intake from a
“normal” level by 30%? The difficulty in getting people to adhere
to something like that is one of the reasons there’s so little
research on CR in people, Dr. Leonard Guarente,
the Novartis Professor of Biology at the Glenn Laboratory for the
Science of Aging at MIT, previously
told Business Insider.

Still, many researchers are inspired by all the growing amount of
data showing that CR or some form of fasting can extend life and
make people healthier. Some think that eating normally most of
the time but cutting calories for a short period of time
regularly, in some form of intermittent fasting, could lead to
the same benefits.

We need to food to live and to grow. But in an odd twist, it
seems that there’s more and more evidence showing that after a
certain point, eating less of it could help us live longer.