Last week, in the prestigious journal Science, researchers posted the latest in the saga of calorie restriction and life extension. Remember the dieting, life-prolonging studies in rodents and the 890 calorie-a-day, life-extending regimens in people?
Now, in a decades-long study of monkeys on a restricted diet, researchers found that those which ate less lived longer -- and healthier.
Here are the details: Back in 1989, scientists gathered 30 “adult” rhesus macaques and gave half open access to a buffet of monkey nutritious foods and the other half the same nutritious diet, but less of it. As some animals began to die off, researchers added another 46 monkey to the study in 1994. Over the next two decades, the scientists tracked the lives and health of the primate. It turns out that today, with 33 monkey left, half of the animals permitted to eat freely have survived, while a striking 80 percent of the monkeys given the same diet, but with 30 percent fewer calories, have ripened into monkey old age.
Beyond added years of life, the calorie-restricted monkeys developed fewer cancerous tumors, showed less heart disease and lowered their risk or incidence of diabetes and impaired blood sugar control. None of the calorie-restrictors got diabetes. Finally early results show a protective effect of calorie restriction on brain health, including preserving memory and problem solving capacity.
This would seem a boon to aging-conscious, health advocates. The researchers themselves are singing the study’s promise: "We have been able to show that caloric restriction can slow the aging process in a primate species," says Richard Weindruch, a professor of medicine in the UW-Madison School of Medicine and Public Health who leads the National Institute on Aging-funded study. "We observed that caloric restriction reduced the risk of developing an age-related disease by a factor of three and increased survival.”
But -- and there is a big “but” -- people need to treat these results with caution. Eating disorders researchers also know of another cluster of studies which show that being underweight can actually double the risk of death -- and that some degree of extra weight is associated with longer life – (heavier people are at a higher risk for death due to diabetes and kidney diseases but a less at risk for non-cardiovascular, non-cancer causes of death, such as infections).
Meanwhile, geriatric researchers such as John Morley, at St. Louis University, who was one of the first to study eating disorders in older patients, has also shown that that intentional weight loss in women older than 60 can hasten hip fractures and can increase the odds of going to an institution for care by 1.6 times. Weight loss in late life also lowers immune function, leading to susceptibility to infectious diseases such as pneumonia.
To make sense of these conflicting studies, then, we have to realize that weight is a question of balance. Morley, who grew up in Africa where attention to starvation is as paramount as attention to obesity, says “Americans often have trouble with keeping two opposite ideas about weight in their minds at once.”
In simple terms, weight loss is good AND bad. Weight loss is good if obesity is an issue. At the same time, weight loss is bad in later life or if a person has grappled with an eating disorder such as anorexia, for example.
The danger for studies such as the monkey one is in overgeneralization. Given a prescription for calorie restriction to live longer, people will go rushing to starve themselves willy nilly– and put undue stress on the body. And then the same people will get sick of the low-cal limits and binge or overeat– leading to more stress on the body. The salient message, says Morley, is weight stability – we must find the balance in eating and body weight and retain that equilibrium throughout life.
Bone appétit!
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Posted by: Shawna30Nielsen | January 10, 2011 at 06:19 PM