Results from a long-running primate study of calorie restriction (CR) are becoming more definitive as the years pass. Two decades in, the reports continue to be consistent with the many, many other CR studies in animals and humans: eating fewer calories while still obtaining adequate nutrition slows down degenerative aging in primates.
Studying aging in monkeys takes patience. Mice and rats only live for a couple of years, while these monkeys can live to 40, and the average life span is 27 years. Now that the surviving monkeys have reached their mid- to late 20s, the Wisconsin group could glean how calorie restriction was affecting their life span. Sixty-three percent of the calorie-restricted animals are still alive compared to only 45% of their free-feeding counterparts. For age-related deaths caused by illnesses such as cardiovascular disease and cancer, the voracious eaters died at three times the rate of restricted monkeys: 14 versus five monkeys, respectively.
Researchers who study aging are split on how much stock to put in the study. Leonard Guarente, a molecular biologist at the Massachusetts Institute of Technology in Cambridge who has studied aging in yeast, believes that not enough monkeys have died yet to make definitive comparisons between the two groups. As of March, when Weindruch's group submitted the paper, about half of the colony was still alive. "The gap [in survival rates] may separate more, but it's still too early to tell," Guarente says. On the other hand, molecular biologist Matthew Kaeberlein of the University of Washington, Seattle, thinks the gap as it stands now is still compelling. He points to the difference in age-related deaths between the two groups as the more relevant statistic. "The fact that they see a significant effect at this point suggests there will be a robust effect when they finish the study," he says.
The original paper in Science won't add much more in the way of useful detail for most of you folk - the commentary in responsible news articles is probably more helpful. If you're familiar with the effects of calorie restriction in other mammals, this is basically a confirmation of what was the expected and most plausible outcome in rhesus monkeys. The practice of calorie restriction remains, as before, a good bet for healthy humans. A great weight of scientific evidence exists to back up that assertion, eating fewer calories won't cost you anything other than time spent learning the best practices, and this strategy is presently available to anyone who wants to try it.
Colman, R., Anderson, R., Johnson, S., Kastman, E., Kosmatka, K., Beasley, T., Allison, D., Cruzen, C., Simmons, H., Kemnitz, J., & Weindruch, R. (2009). Caloric Restriction Delays Disease Onset and Mortality in Rhesus Monkeys Science, 325 (5937), 201-204 DOI: 10.1126/science.1173635