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Caloric Restriction Doesn't Extend Lifespans

Updated on August 28, 2011
Eat, drink and be merry
Eat, drink and be merry
Caloric Restriction or Calorie Restriction (CR) is a method of extending your life span and improving your overall health by reducing your intake of food. Not surprisingly, lower blood sugar, blood pressure and serum cholesterol have been observed among those who practice CR. In many studied animals, CR has also extended lifespans. The question is whether CR extends the life spans of humans as well (well, at least for those very few that are able to stick to semi-starvation).

Don't bother starving yourself. You're not a rat.

It all began with two Cornell University scientists and their research in 1934, that showed that underfed rats lived twice as long as those with ample diets. Subsequent research over the following decades supported the same conclusion: rats, mice, insects, spiders and other animals were able to extend their lifespans by 30% or more through severe reduction of calories. Since rats and mice are, genetically and physiologically speaking, remarkably similar to humans (a scary thought in itself), the next logical conclusion was that caloric restriction would do the same for people. Several books, like The Longevity Diet and Beyond the 120 Year Diet, sought to apply these findings to people with the will to live long lives, and the willpower to drastically reduce their ingestion of food.

Recent research, however, performed at UCLA, seems to reject the connection between rodents and humans: what's good for the rat is not necessarily good for man. UCLA evolutionary biologist John Phelan, along with Michael Rose, at UC-Irvine, developed a mathematical model for humans describing the relationship between caloric intake and lifespan, and populated the model with data from published studies on human longevity, and figures from related research on the connection of rat longevity and caloric restriction, which, incidentally, Phelan researched for his dissertation at Harvard ten years ago. While rats will live longer the more food they're denied (to the point, of course, that they starve to death), humans can only expect a very modest increase in longevity-about 3%--by engaging in a dietary regimen that less than 1% of the population has the psychological stamina for.

A cloud with a silver lining: We're not enough alike to benefit from caloric restriction
A cloud with a silver lining: We're not enough alike to benefit from caloric restriction

Why does it work for rats, and not us?

If humans and rats are on the same branch of the evolutionary tree, what exactly accounts for this huge difference?

There are a few possible explanations. Dr. Phelan offers one: when rats are underfed, one primary biological process that the starving rat shuts down is the reproductive one. Reproduction is enormously taxing on the rat's body: it reaches sexual maturity at one month of age, and produces a litter equal to its own weight every six weeks. Humans, by contrast, endure far less trauma to their bodies by reproducing.

Another possible explanation: when rats are underfed, rats can signficantly lower their body temperatures to reduce the metabolic burden while they're looking for food. At lower body temperatures, the body produces far fewer free radicals, which damage tissues and lead to aging (according to the free radical theory of aging). However, human beings do not have this temperature-lowering mechanism. While less fuel will undoubtedly slow metabolism in humans, it will not do so to the same extent as in rats. Rajindar Singh Sohal, a researcher in aging currently with USC, supports this conclusion.

What can we learn from this?

What kind of useful learnings can we draw from this recent finding?

First, although severe caloric restriction might not be worth the trouble, avoiding overweight and obesity is still a strong guarantor of a longer life.

Second, supplements like resveratrol still might be worth taking, as a caloric restriction-mimetic.

Third, starving yourself will deny you the subtle pleasure of having to pop open the top button on your jeans after a really big Thanksgiving dinner... (a good sense of humor is a key to longevity, don't forget that!)


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    • MelonieGilchrist profile image

      Gamrgurl 5 years ago

      I have heard people use this as an excuse for dieting in the past and always explain that it just isnt right. Glad someone put it out there in writing!

    • profile image

      Ed 6 years ago

      How paid for the study? Interesting comment: "Second, supplements like resveratrol still might be worth taking, as a caloric restriction-mimetic."...

    • NCBIer profile image

      NCBIer 7 years ago

      Interesting article! I know its been a while since you wrote it, but the topic is still relevant, if not more so. You could cut the caloric intake for a majority of Americans by 20% (at least) and they would not be anywhere near starvation and yet, could add many years to their life expectancy. Is quality of life more important than length? Most would agree. However there are many things you can do to now to improve the quality of life in your future, a compromise say, between popping that top button open once or twice (or even several) times a year compared to doing so once a week or more!

    • profile image

      wajay_47 11 years ago

      This hub is best read while eating a sausage with mushroom pizza! - very informative and a very nice hub.

    • livelonger profile image

      Jason Menayan 11 years ago from San Francisco

      Gredmondson: Maybe, maybe not. I think the jury's still out, but she might have just been lucky too.

      Gwinn: it looks like rhesus monkeys join rats & spiders in the "lucky bunch" (well, if you can call that lucky... ;-)

      Glass & Jstankevicz: Haha! I agree! You did notice the caption on my first pic, right?

    • jstankevicz profile image

      jstankevicz 11 years ago from Cave Creek

      Right or wrong, I embrace any written claim that supports my habits and instincts! Great hub, as usual, LL.

    • profile image

      Gwinn 11 years ago

    • glassvisage profile image

      glassvisage 11 years ago from Northern California

      Yay! I like this; makes me happy :)

    • gredmondson profile image

      gredmondson 11 years ago from San Francisco, California

      Thanks for the well written Hub. I remember years ago reading that Rose Kennedy lived so long because she severely restricted her calories. I guess that wasn't the main reason.

    • vic profile image

      vic 11 years ago

      This is great news. Thanks!