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Does Caloric Restriction Prolong Life?

A Picture of Health?
A Picture of Health?

You may have heard Oprah’s Dr. Oz talking about an amazing new diet that, he claims, might allow us to live 150 years. I noticed that Dr. Oz seemed to be doing his best to highlight the benefits of this diet and downplay any risks, though he wasn’t following the diet himself – and I think I know why.

The diet he’s referring to is called “the calorie restriction diet,” a diet that requires you to limit your calories to 20 or 40 percent fewer than what’s currently recommended as a healthy amount, often as low as 1200 calories per day for women and 1800 for men.

This severe caloric restriction is said to engage the “sirtuin pathway,” a metabolic reaction to stress which, according to Dr. Oz, tells the body, “Don’t make more babies because you don’t have the excess abundant energy to do that—just live longer.”

Of course, though many people are dedicating themselves to these restrictions already, it’s anybody’s guess whether it will actually extend their lives. What researchers do know for sure is that if you genetically engage the sirtuin pathway in yeast, you can effectively slow all metabolic processes including reproduction and death. Whether these yeast “live” longer because they’ve been made more healthy is not well understood.

That’s why, to bolster their case, the Biotech companies funded animal research. One study the calorie restriction proponents like to point to a primate study done at the Wisconsin National Primate Research Center(1).

What does the sirtuin pathway have to do with this study? Nothing. None of the monkeys in the study were given anything approximating the kind of calorie restriction that might engage the sirtuin pathway. One group was given a standard pellet regimen, and the other was overfed.

So it’s not really a sirtuin pathway study. How, then, do these scientists trick TV doctors and other media talking heads into bringing this study up and folding it into discussions about life extension?

They monkey with the language, saying that study animals have been placed on a calorie restriction diet when, in reality, they’re diets are restricted relative only to the animals in the next cage – the ones who get all the pellets they want whenever they want.

The claim is that the study group monkeys (the monkeys on the “calorie restriction” diet) went hungry, and were being compared to a control group of monkeys on a normal diet. In reality, they allowed one group of monkeys to become so obese (notice the rolls of belly fat on the monkey on the right) that they were bound to live shorter lives than their relatively trim lab mates. Then, the researchers can attribute this miracle to the wonders of Dr. Oz’s sirtuin pathway.

Here’s where the biotech companies really get excited because if we actually buy the arguments made in these seriously flawed studies then maybe, in a few years time, we’ll also be buying billions of dollars worth of pills promising to turn our sirtuin pathways on without the need to go hungry.

Life Extension Claims are Fictitious

So there’s no real life extension. It’s only life extension relative to premature death. This deception is just one of many that I found from reading the scientific papers with a careful eye for detail.

The holes in this study seem big enough to build on of Oprah’s houses in. How could Dr. Oz have missed them? I don’t know, honestly, because they admit the study flaws right in the opening language.

More than 70 years ago, it was discovered that reducing energy intake during
adult life can increase the life span of laboratory rodents. The ability of
caloric restriction (CR) during adult life to lengthen life span has been observed
consistently in many different species of mammals. In all such energy-
restriction studies described in this chapter the control group was fed ad libitum
and the CR diet group received amounts of micronutrients equivalent to those
consumed by the control group. It should therefore be kept in mind that, with
regard to food intake, ad libitum feeding in the laboratory is not the norm for
rodents in the wild. Instead, the control animals are overfed and overweight.

“It should therefore be kept in mind that…the control animals are overfed and overweight.” Darn right it should, since this small fact completely undermines the popular interpretation of the study, that calorie restriction makes sense for people who aren’t overeating.

All such calorie-restriction studies over the course of the past century – and there have been hundreds – are built around the same flaws and produce the same swirling alphabet soup of self-contradiction and sleight of hand that feeds the front-line troops of the Biotech campaign.

I blame ad-libitum
I blame ad-libitum

Regardless of the researchers lofty claims of super-longevity, such studies’ true findings are far more humble. They show only that ad-libitum diets make animals fat, particularly when they’re caged and the stuff they’re eating is a little more nourishing than cardboard and a lot less nourishing than their natural diet.

It’s a little like locking your cat in the bathroom with an endless supply of dried chow. Come back three weeks later and you’ll find a cat that’s bored, resentful, and bigger. What, as a scientist, might you conclude from that? That you should start starving yourself and your family? Or might you infer something else?

Citing these studies as evidence, some celebrity doctors are implying that if we get terrible chronic diseases it is due in part to the fact that we lack the discipline to starve ourselves.

It’s also not a great idea to trade in your kitchen crockery for an array of digital milligram scales and teaspoon measurements, denying yourself the pleasure of a healthy diet because a bunch of manipulated studies told you that you should.

Here’s a better prescription: ape the lifestyles of people who live the longest. Eat authentic cuisine made with fresh, local ingredients, laugh, love, exercise and live passionately. And by all means, do restrict your intake of junk science.

biscuit and granola
Un-Natural Diets


1.Caloric Restriction Delays Disease Onset and Mortality in Rhesus Monkeys Science 10 July 2009:
Vol. 325. no. 5937, pp. 201 – 204

2. Calorie restriction and cardiometabolic health European Journal of Cardiovascular Prevention and Rehabilitation 2008, 15:3–9 “Hundreds of studies have shown that CR, defined as a reduction in calorie intake below ad libitum (AL) intake without malnutrition, is the most reliable and effective intervention for improving metabolic health, preventing carcinogenesis and increasing life span in rats, mice, fish, flies, and worms”

3. ENERGY INTAKE, MEAL FREQUENCY, AND HEALTH: A Neurobiological Perspective, Annu. Rev. Nutr. 2005. 25:237–60

Dr. Cate

With over two decades of clinical experience and expertise in genetic and biochemical research, Dr. Cate can help you to reverse metabolic disease and reshape your body.

This Post Has One Comment

  1. I did this diet about 10 years ago after seeing Ray Wolford on TV. Dropped a lot of weight, but everyone thought I was sick. Then I watched a clip on 60-minutes of some folks who were practicing this, they were ooing and ahhing over a little hunk of broccoli rabe. Plus they looked like Gollum. I looked like Gollum. Seeing as how I play golf and usually carry my bag, I abandoned CR, for fear I might collapse under the weight of my own golf bag.

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