The Skinny On Calorie Restriction

By 13bobby ( [CC-BY-2.0 (], via Wikimedia Commons

Rhesus monkey By 13bobby ( [CC-BY-2.0 (, via Wikimedia Commons

Last week in my post about the Rate-of-Living Theory of why we age, I expected to tell readers that caloric restriction works for yeast, worms, and rodents, but had never showed promise in primates. I based my assumption on an experiment by the National Institute of Aging that recorded no difference in survival and very little significant increase in health due to calorie restriction in monkeys. A more recent publication from a 25 year study at the University of Wisconsin in March 2014 reports the opposite. Monkeys allowed to eat as much as they wanted had a risk of disease 2.9 times greater and a threefold increase in risk of death than monkeys on a calorie restricted diet. Why the difference?

The key might be in one experimental method. All 76 Rhesus Monkeys in the UW study entered as adults. Researchers found out how many calories each monkey craved and ate on it’s own, then reduced that by 30 percent in the experimental group. In the NIA study, the number of calories each of the monkey was allotted came from a standardized food intake chart.

UW reasearchers tried to reconcile the older study to their own, and found that all the monkeys in the NIA study weighed less than those in their own study and often less than monkeys in an online database of weights for research monkeys. Five of the monkeys in the NIA study lived 40 or more years. That, as far as the UW researchers know, is unusual. Their conclusion? The monkeys in the earlier NIA study may have all been subjected to calorie restriction to differing degrees.

It will be interesting to watch the continuing interpretation and review of these two studies. Even if the NIA study was administering calorie restriction to both control and experimental groups, the results could help us understand how different levels of caloric restriction work. Both of these studies could help us confirm that eating fewer calories changes the way we age, and bring us closer to unlocking that mechanism so we could use it too, without the exreme diets.


University of Wisconsin-Madison. “Monkey caloric restriction study shows big benefit; contradicts earlier study.” ScienceDaily. ScienceDaily, 1 April 2014.


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