This is a multipart answer. Since this week we are just getting our appetites going with anecdotes and a little science, let me talk about a corollary that has intrigued me since I began studying aging.
As with the caloric restriction studies, the mechanisms of which began to come to light in the ’90s and early 2000’s, stress was also an overarching theory around that time. To study longevity for one’s dissertation was highly appealing, but the long-lived rodents that were genetically tweaked or fed less lived over 3 years (normal lifespan was around 2 years), which would mean a longer time to finish one’s dissertation. So enticing as longevity studies may have seemed at the time, I chose to pursue the effects of stress on aging… and my model was one that aged quickly because its mitochondria (power supply for the body’s cells) were extra-stressed.
When an engine is not performing to its’ best possible ability, it tends to be less efficient. When it is less efficient, it produces waste (in case of mitochondria, reactive oxidants). Waste – oxidants – produced by mitochondria damage them further, making them still less efficient, so they produce more waste (oxidants). Now, the young and healthy cells are generally well-equipped to handle a little stress form these oxidants. But when things spiral out of control… and these pesky oxidants get to be too many to handle, then the situation requires emergency management. This condition is called oxidative stress. The outcomes can be many: mitochondria can shut down; cells are programmed to self destruct; some cells carry on with less than ideal machinery and are merely “senile”…
Now, it seems that if mitochondria don’t respire very fast, the cells live longer as they produce fewer damaging “oxidants.” Organisms with faster mitochondrial respiratory rates tend to have shorter lifespans and vice versa. Reminiscent of Pranayama (ancient breathing practices of Yoga)…?
Some articles to read on the topic:
Puzzles, promises and a cure for ageing; Jan Vijg and Judith Campisi
Mitochondrial Turnover and Aging of Long-Lived Postmitotic Cells: The Mitochondrial–Lysosomal Axis Theory of Aging
Alexei Terman, Tino Kurz, Marian Navratil, Edgar A. Arriaga, and Ulf T. Brunk