WisBusiness: Calorie-Restricted Monkeys Becoming Healthier "Senior Citizens"
By Alyssa Kohler
MADISON – Nutritionists have long believed that a lean diet is the key to living longer, but proving this correlation in an increasingly obese society has been more than problematic for scientists.
Thanks to recent studies done on non-human primates, scientists have uncovered more evidence supporting the “eat less, live longer” claim.
A calorie-restriction experiment that began in 1989 with a group of rhesus monkeys under the care of the Wisconsin National Primate Research Center is entering the “golden years” of the study, and the monkeys are showing no signs of slowing down.
These are the new findings of “Project 2,” a National Institutes on Aging calorie restriction and aging project grant that earned its third successful five-year renewal last summer under the leadership of Richard Weindruch.
Led by Dale Schoeller, a UW-Madison professor of nutritional sciences, and aided by Ricki Colman, a scientist at the Wisconsin Primate Research Center, Project 2 continues to follow 18 of the original 30 rhesus monkeys from the famous 1989 experiment as they begin to near the primate equivalent of “retirement” age.
“The monkeys in the oldest group are now about 25, being equivalent to 60-year-old humans,” Schoeller said.
Both the control and calorie-restricted (CR)monkeys are given the same kind of “monkey chow,” a nutritious and well-balanced dry meal comprised of softball-sized biscuits. The CR monkeys are simply given less of it, their portions being reduced by roughly 30 percent. Healthy snacks such as apples and raisins supplement this diet in both monkey sets.
How well are these calorie-restricted monkeys aging compared to their control group counterparts? They are doing exceedingly well, according to Schoeller. The CR monkeys are showing no obesity, better blood glucose control and, based on studies from the other projects funded by the grant, fewer cellular defects and less muscular atrophy.
“None of these monkeys seem ready for a rocking chair, yet, so we’ll continue to follow these changes as they age further,” added Schoeller.
Schoeller and his associates have been investigating the effects of aging even further, focusing on the way the calorie-restricted monkeys expend their energy compared to those in the control group.
“We expected the CR monkeys not to decrease activity energy expenditure as much as the control monkeys with advancing chronological age,” Schoeller explained.
They were surprised to find, however, that this was not the case. Both the control and the CR monkeys showed similar decreases in TEE (total energy expenditure) levels, despite the better health of the restricted group.
“The reason for this is not clear,” says Schoeller, “but it does suggest that this gradual decrease in (total energy expenditure) is a very consistent phenomenon of aging and not just a product of an accumulation of chronic diseases.”
While this study has only seems to prove what the medical community has known for so long, its true excitement lies in its ongoing study.
Scientists can now work on trying to understand why our bodies react better when given fewer calories, perhaps understanding more about the chronic diseases that oft accompany aging.
And while scientists would not be quick to recommend this extreme a diet to the human population, the study does also exemplify the importance of staying lean if one wishes to age well.
Kohler is a student in the UW-Madison Department of Life Science Communications.