Researchers in Wisconsin and Maryland are reporting the results of a long running experiment in calorie restriction using monkeys. One set of monkeys got all the chow they wanted, while others were restricted to eating 30 percent fewer calories than they would have preferred. As the New York Times reports:
The results from one of the two studies, conducted by a team led by Ricki J. Colman and Richard Weindruch at the University of Wisconsin, were reported Thursday in Science. The researchers say that now, 20 years after the experiment began, the monkeys are showing many beneficial signs of caloric resistance, including significantly less diabetes, cancer, and heart and brain disease. "These data demonstrate that caloric restriction slows aging in a primate species," they conclude….
"It says much of the biology of caloric restriction is translatable into primates," he said, "which makes it more likely it would apply to humans."
In terms of deaths, 37 percent of the comparison monkeys have so far died in ways judged to be due to old age, compared with 13 percent of the dieting group.
Not everyone is convinced since theactual death rates were not significantly different:
Though a smaller number of dieting monkeys have died, the difference is not statistically significant, the Wisconsin team reports.
The Wisconsin researchers say that some of the monkey deaths were not related to age and can properly be excluded. Some monkeys died under the anesthesia given while taking blood samples. Some died from gastric bloat, a disease that can strike at any age, others from endometriosis. When the deaths judged not due to aging are excluded, the dieting monkeys lived significantly longer.
Some biologists think it is reasonable to exclude these deaths, but others do not. Steven Austad, an expert on aging at the University of Texas Health Science Center, said some deaths could have been due to caloric restriction, even if they did not seem to be related to aging. "Ultimately the results seem pretty inconclusive at this point," Dr. Austad said. "I don't know why they didn't wait longer to publish."
I know several people who practice calorie restriction; some of whom take scales to restaurants to weigh their food. This new research suggests that they may succeed in extending their lives. Of course, those of us who still feed ad libitum take solace from the quip: Calorie restriction may not actually extend your life; it may just make it seem that way.
In any case, I am personally hoping that research on sirtuins pans out. Sirtuins are thought to activate the same metabolic pathways that calorie restriction does. If they work, they may allow us free-feeders to eat all the beer and pizza we want for a very long time.