Society member Bob Cavanaugh said: "Some people are doing it
strictly to enhance longevity," Cavanaugh said by phone from his
home near Moorehead City in North Carolina.
"Others do it to avoid age-related disease, or because they
already have diabetes, high cholesterol or clogged arteries and
want to clean up their bodies by using diet."
A worldwide epidemic of obesity-related diseases has put a
spotlight over the last decade on the link between food and
health.
"In rich countries, 90 percent of the population probably eats,
on average, about 50 percent too much," noted Christiaan
Leeuwenburgh, head of the biology of aeging division at the
University of Florida's College of Medicine.
"Even if they were to reduce their calorie intake by half, they
would still only be at baseline," the optimal balance between
energy input and output, he told AFP.
A wealth of scientific evidence has confirmed that maintaining
that balance helps prevent type-2 diabetes, cardiovascular disease
and cancer.
But experiments with both animals and humans have also shown
that pushing one's calorie intake 10 to 20 percent below that
baseline threshold -- without lowering nutrients -- may provide
additional health advantages.
Luigi Fontana, a professor in the Division of Geriatrics and
Nutritional Science of Washington University in St. Louis,
Missouri, has led or co-authored more than a dozen studies on
reduced calorie intake in humans.
He is also one of a handful of researchers studying longterm
impacts by monitoring a group of nearly 50 adults who have been on
calorie restriction diets for at least a decade.
"Most are middle-aged, but they have the cardiovascular profile
of a teenager," he said by phone.
Blood pressure, cholesterol, blood sugar and insulin levels are
all low while so-called "good" cholesterol remains high, he said.
Diabetes and cancer rates are down too.
Studies published earlier this year point to other, specifically
age-related, benefits as well.
One shows that cutting calorie intake 20 percent cut damage in
DNA and RNA caused by oxidation in half compared to control
groups.
Oxidative damage to DNA, proteins and other cellular building
blocks accumulate over time and are thought to be a major driver of
ageing.
A second study by Fontana, published in July in Aeging Cell,
shows that a combination of calorie reduction and limiting protein
intake lowers levels of insulin-like growth factor, commonly known
as IFG-1.
IFG-1 is a high-risk marker for prostate, breast and colon
cancer, and plays a key role in regulating cell growth linked to
the ageing process.
Cavanaugh, 61, an ex-marine, started the diet eight years ago
after a 15-year history of high cholesterol and blood pressure.
At first he improvised. "I designed a diet I thought was very
nutritious, but I had a problem with hunger and would sometimes go
on candy binges," he said.
Not until he began to keep track not just of calories but
vitamins, minerals and amino acids did the diet really work.
"My level of vitality soared," he said, insisting he has more
energy today than 20 years ago.
Consuming less calories does not necessarily mean eating less
food, he said. While he only takes in two meals a day, he tucks
away large quantities of fruits and vegetables, along with smaller
portions of lean meats and fish.
Refined, processed foods high in sugar, fat or salt -- junk
food, in other words -- is off the menu.
The average calorie intake for men is about 1,800, and for women
between 1,200 and 1,600, depending on height.
Despite the proven health benefits, the jury is still out on
whether counting calories enhances longevity, which some scientists
think has a genetically-imposed ceiling.
"It may be unlikely that it will extend human lifespan
significantly," said Jan Vijg, a scientist at the Buck Institute
for Age Research who recently co-authored an overview article on
ageing in the London-based journal Nature.
The very fact humans live so long makes it difficult to conduct
controlled experiments, he said.
Tests with monkeys underway for two decades give no indication
that life in primates can be extended by the 30 or 40 percent seen
in rats and mice.
"Will this add 10 years to your life? Nobody knows," said
Leeuwenburgh, adding that reducing calories late in life could make
it difficult to maintain needed muscle mass.
"But one thing is sure -- calorie restriction will help you
reach your maximum lifespan potential, which is different for all
of us depending on our genetic profile," he said.
The Calories Restriction Society has about 3,500 dues-paying
members, and its website gets about 4,500 hits a day.