I posted a blog a while ago about diets. I talked briefly about a calorie restriction diet when I mentioned an article, “Study Finds Low-Calorie Diet Extends Lifespan of Monkeys“.

Here’s some more. The New York Times posted an article about a recent study:

…[the study] is investigating how (and if) a spartan diet affects the aging process and its associated diseases. To the [study] researchers, these are quite distinct. The aging process, which researchers sometimes call “primary” or “intrinsic” aging, refers to the damage that ordinarily accumulates in our cells as we grow older, a natural condition that seems to have limited the maximal lifespan of humans to 120 years. Diseases that accompany the aging process — often called “secondary aging” — are those afflictions increasingly prevalent in the elderly, like cancer, diabetes and cardiovascular disease.
[...]
In a study on rats, [researchers] compared animals that were lean because of exercise with those that were equally lean from calorie restriction. “Both had an increase in average life span,” Fontana said, but only calorie restriction was able to slow down aging and increase maximal life span. That suggested that “leanness” was not in and of itself determining the rate of aging. “Speaking of humans,” Fontana added, “if you are lean because you are exercising, of course you are doing good, because you’re preventing types of diabetes, some kinds of cardiovascular disease and maybe some types of cancers. But the data suggest that calorie restriction is more powerful. And the people on C.R. are more powerfully protected from diseases than the exercisers.”

Some more excerpts from “The Calorie-Restriction Experiment“:

The medical literature on calorie restriction sometimes cites an experiment conducted in Minnesota in the 1940s to study the effects of starvation, especially with the war-torn populations of Europe in mind. The men — all lean to begin with, all volunteers (they were conscientious objectors to World War II) — were subjected to about a 40 percent decrease in caloric consumption. The state of near starvation led a few of the subjects to the threshold of insanity. They became irritable and depressed; some began to lie and cheat; at least one engaged in acts of self-mutilation. Some of the potential insights of the Calerie study, therefore, are psychological as much as physiological.

Holy crap, too much is bad for you. The study mentioned in the article shoots for a 25% calorie reduction.

To put it to the medical doctors overseeing the study — could this ever be prescribed to a larger population, either as a preventive tool or a treatment? — is to walk into a wall of skepticism. “Ninety-nine percent can’t do it,” John Holloszy, a medical doctor who is the lead investigator at Washington University, told me. “The people in the study are not going to stick with it” after they leave. Other medical doctors involved with Calerie told me they were also dubious, believing that a low-calorie regimen requires too much in the way of individual effort and too much in the way of medical resources and counseling to make it practical for many Americans. When I spoke with Robert Krikorian, a longtime Calorie Restriction Society member who is not in the Calerie study but who happens to be a neuropsychologist, he pointed me to some behavioral studies that showed how inattentive we are in regard to what we ingest on any given day. “I don’t think humans are designed to pay attention to how much they eat,” he said, adding that for most people this natural tendency would chafe against the organizational requirements of calorie restriction, thus limiting its appeal.

I’m a little on the fence about this diet. The only thing I agree on is that it may reduce the risk of heart-related illnesses:

Fontana connected his point to his continuing observations of some Calorie Restriction Society members. “In terms of cardiovascular diseases — the No. 1 cause of death; 4 out of 10 people die of it in the U.S. and Europe — we know that they will not die of cardiovascular death…

TL;DR:
Reducing your calorie intake (up to ~25%) may extend your lifespan by reducing the risk of diseases.

Some more reading:
Calorie Restriction Society
The Fast Supper
Is a Calorie Restriction Diet Starvation?
CALERIE: The NIH Calorie-Restriction Experiment. Lessons for Health, Slowing Down the Aging Process, Longevity, and Disease Prevention
CALORIE RESTRICTION AND THE LOWERED CALORIE DIET REGIME WILL BE PROVEN TO BE VERY BENEFICIAL TO QUALITY OF LIFE AND INCREASED LIFE EXPECTANCY
What Do You Think Of Calorie Restriction Diet To Live Longer?
Is My Diet Hurting Me?
The Calorie Restriction Diet: Insight Into Life Extension Through Diet
Caloric restriction diet doesn’t work