More on Heart Rate Variability in Calorie Restriction Practitioners
You might recall research published a couple of months ago on calorie restriction and heart function. It illustrated (again) that people who practice calorie restriction over the long term have physiologically younger cardiovascular systems - meaning notably less low-level cellular damage and better function than their peers of a similar chronological age.
Heart rate variability (HRV) is a marker for cardiac autonomic functioning. The progressive decline in HRV with aging and the association of higher HRV with better health outcomes are well established. [Researchers] compared 24-hr HRV in 22 CR individuals aged 35 - 82 yrs and 20 age-matched controls eating Western diets (WD). The CR group was significantly leaner than the WD group. Heart rate was significantly lower, and virtually all HRV significantly higher in the CR than in the WD group. HRV in the CR individuals was comparable to published norms for healthy individuals 20 years younger.
If there was a drug that did that, its financials would be staggering - and you'd never hear the end of it. It would be publicized and popularized in every corner of the world. But just ask someone to exercise a little willpower and planning in their diet to gain the same results ... and therein lies a lesson with regard to human nature.
I notice that the institutional publicity machine at Washington University in St.Louis has caught up with this research; if you'd like a little more commentary from the researchers involved, that's the place to look:
"This is really striking because in studying changes in heart rate variability, we are looking at a measurement that tells us a lot about the way the autonomic nervous system affects the heart," says Luigi Fontana, MD, PhD, the study's senior author. "And that system is involved not only in heart function, but in digestion, breathing rate and many other involuntary actions. We would hypothesize that better heart rate variability may be a sign that all these other functions are working better, too."...
"Higher heart rate variability means the heart can adjust to changing needs more readily," says lead author Phyllis K. Stein, PhD. "Heart rate variability declines with age as our cardiovascular systems become less flexible, and poor heart rate variability is associated with a higher risk of cardiovascular death."
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"The idea was to learn, first of all, whether humans on CR, like the calorie-restricted animals that have been studied, have a similar adaptation in heart rate variability," Fontana says. "The answer is yes. We also looked at normal levels of heart rate variability among people at different ages, and we found that those who practice CR have hearts that look and function like they are years younger."
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"In many of our studies, we have found that a number of metabolic and physiologic changes that occur in calorie-restricted animals also occur in people who practice CR," Fontana says. And he says the finding that heart rate variability is better in people who practice CR means more than just that their cardiovascular systems are flexible. He says the better ratio suggests improved health in general.
"But we can't be absolutely positive that the practice of CR is solely responsible for the flexibility of the cardiovascular system," Stein says. "People who practice CR tend to be very healthy in other areas of life, too, so I'm pretty sure they don't say to themselves, 'Okay, I'll restrict my calorie intake to lengthen my life, but I'm still going to smoke two packs a day.' These people are very motivated, and they tend to engage in a large number of very healthy behaviors."
The point on calorie restriction practitioners practicing good health across the board is a fair one - peeling apart the beneficial effects of regular exercise from the beneficial effects of calorie restriction in humans, for example, is an interesting challenge. Still, it would be hard, I think, to find a population of humans who are exceptionally health-conscious without practicing calorie restriction and who nonetheless exhibit a youthful physiology to the degree seen in calorie restricted people. There are different classes of mechanism at work here.