Sorry folks, but science has just done in the well beloved theory of
calorie restriction as a natural promoter of a longer life. This
experiment was a good as could be devised and it came a cropper.
Weight management in the last trimester of life is strongly indicated
as well it should be for lots of excellent biological reasons. For
those that care do Google arclein diet.
Otherwise starving yourself serves little utility whatsoever.
Severe Diet Doesn’t
Prolong Life, at Least in Monkeys
By GINA KOLATA
Published: August 29,
2012
For 25 years, the
rhesus monkeys were kept semi-starved, lean and hungry. The males’
weights were so low they were the equivalent of a 6-foot-tall man who
tipped the scales at just 120 to 133 pounds. The hope was that if the
monkeys lived longer, healthier lives by eating a lot less, then
maybe people, their evolutionary cousins, would, too. Some
scientists, anticipating such benefits, began severely restricting
their own diets.
Enlarge This Image
National Institute on
Aging/NIH
A 23-year study
comparing calorie restricted rhesus monkeys, left, to normally-fed
monkeys, has shown that calorie restriction may not increase one's
lifespan.
The results of this
major, long-awaited study, which began in 1987, are finally in. But
it did not bring the vindication calorie restriction enthusiasts had
anticipated. It turns out the skinny monkeys did not live any longer
than those kept at more normal weights. Some lab test results
improved, but only in monkeys put on the diet when they were old. The
causes of death — cancer, heart disease — were the same in both
the underfed and the normally fed monkeys.
Lab test results
showed lower levels of cholesterol and blood sugar in the male
monkeys that started eating 30 percent fewer calories in old age, but
not in the females. Males and females that were put on the diet when
they were old had lower levels of triglycerides, which are linked to
heart disease risk. Monkeys put on the diet when they were young or
middle-aged did not get the same benefits, though they had less
cancer. But the bottom line was that the monkeys that ate less did
not live any longer than those that ate normally.
Rafael de Cabo, lead
author of the diet study, published online on Wednesday in the
journal Nature, said he was surprised and disappointed that the
underfed monkeys did not live longer. Like many other researchers on
aging, he had expected an outcome similar to that of a 2009
study from the University of Wisconsin that concluded
that caloric restriction did extend monkeys’ life spans.
But even that study
had a question mark hanging over it. Its authors had disregarded
about half of the deaths among the monkeys they studied, saying they
were not related to aging. If they had included all of the deaths,
there was no extension of life span in the Wisconsin study, either.
“This shows the
importance of replication in science,” Steven Austad, interim
director of the Barshop Institute for Longevity and Aging Studies at
the University of Texas Health Science Center in San Antonio. Dr.
Austad, who was not involved with either study, said that the
University of Wisconsin study “was not nearly as conclusive as it
was made out to be” and that the new study casts further doubt on
the belief that caloric restriction extends life.
But other researchers
still think that it does, and one of the authors of the new study,
Julie A. Mattison, said it was still possible that some benefit would
be revealed. The study is continuing until the youngest monkeys are
22 years old. While the data pretty much rule out any notion that the
low-calorie diet will increase average life spans, there still is a
chance that the study might find that the diet increases the animals’
maximum life span, she said.
Meanwhile, some others
said that the Wisconsin study made them reluctant to dismiss the idea
that low-calorie diets result in longer life.
“I wouldn’t
discard the whole thing on the basis of one study, when another study
in the same species showed an increase in life span,” said Eric
Ravussin, director of the nutritional obesity research center at the
Pennington Biomedical Research Center in Louisiana. “I would still
bet on an extension of life.”
The idea that a
low-calorie diet would extend life originated in the 1930s with a
study of laboratory rats. But it was not until the 1980s that the
theory took off. Scientists reported that in species as diverse as
yeast, flies, worms and mice, eating less meant living longer. And,
in mice at least, a low-calorie diet also meant less cancer. It was
not known whether the same thing would hold true in humans, and no
one expected such a study would ever be done. It would take decades
to get an answer, to say nothing of the expense and difficulty of
getting people to be randomly assigned to starve themselves or not.
Researchers concluded
the best way to test the hypothesis would be through the monkey
studies at the University of Wisconsin and the National Institute on
Aging, although the animals would have to be followed for decades.
It was a major
endeavor. The National Institute on Aging study involved 121 monkeys,
49 of which are still alive, housed at a facility in Poolesville, Md.
Those that got the low-calorie diet did not act famished, Dr. de Cabo
said. They did not gobble their food, for example, but ate at the
same speed as the control animals, even though their calories had
been cut by 30 percent.
As the studies were
under way, some human enthusiasts decided to start eating a lot less,
too.
In those same years,
though, studies in mice began indicating there might not be a
predictable response to a low-calorie diet. Mice that came from the
wild, instead of being born and raised in the lab, did not live
longer on low-calorie diets. And in 2009, a study of 41 inbred
strains of laboratory mice found that about a third had no
response to the diets. Of those that responded, more strains had
shorter life spans than had longer ones when they were given less
food.
The response to that
study was “absolute disbelief,” Dr. Austad said. “Even though
the authors are well-respected calorie restrictors, people said the
result was not interesting, that there was something weird about the
mice.”
Now, with the new
study, researchers are asking why the University of Wisconsin study
found an effect on life span and the National Institute on Aging
study did not.
There were several
differences between the studies that some have pointed to as possible
explanations.
The composition of the
food given to the monkeys in the Wisconsin study was different from
that in the aging institute’s study.
The University of
Wisconsin’s control monkeys were allowed to eat as much as they
wanted and were fatter than those in the aging institute’s study,
which were fed in amounts that were considered enough to maintain a
healthy weight but were not unlimited.
The animals in the
Wisconsin study were from India. Those in the aging institute’s
study were from India and China, and so were more genetically
diverse.
Dr. de Cabo, who says
he is overweight, advised people that if they want to try a
reduced-calorie diet, they should consult a doctor first. If they can
handle such a diet, he said, he believes they would be healthier,
but, he said, he does not know if they would live longer.
Some scientists still
have faith in the low-calorie diets. Richard Weindruch, a director of
the Wisconsin study, said he was “a hopeless caloric-restriction
romantic,” but added that he was not very good at restricting his
own calories. He said he might start trying harder, though: “I’m
only 62. It isn’t too late.”
Then there is Mark
Mattson, chief of the laboratory of neurosciences at the National
Institute on Aging, who was not part of the monkey study. He believes
there is merit to caloric restriction. It can help the brain, he
said, as well as make people healthier and probably make them live
longer.
Dr. Mattson, who is
5-foot-9 and weighs 130 pounds, skips breakfast and lunch on weekdays
and skips breakfast on weekends.
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