HARVARD MAGAZINE (SEPT – OCT 2020): From the book EXERCISED: Why Something We Never Evolved to Do Is Healthy and Rewarding by Daniel E. Lieberman, to be published on September 8, 2020 by Pantheon Books:
‘….many of the mechanisms that slow aging and extend life are turned on by physical activity, especially as we get older. Human health and longevity are thus extended both by and for physical activity.’
The graph breaks total energy expenditure (TEE) into two parts: active energy expenditure, and resting metabolism. Resting metabolism remains elevated for hours even after exercise ceases, burning additional calories in a phase known as excess post-exercise oxygen consumption (EPOC).
Exercise is like scrubbing the kitchen floor so well after a spill that the whole floor ends up being cleaner. The modest stresses caused by exercise trigger a reparative response yielding a general benefit.
In order to elucidate the links between exercise and aging, I propose a corollary to the Grandmother Hypothesis, which I call the Active Grandparent Hypothesis. According to this idea, human longevity was not only selected for but was also made possible by having to work hard during old age to help as many children, grandchildren, and other younger relatives as possible survive and thrive. That is, while there may have been selection for genes (as yet unidentified) that help humans live past the age of 50, there was also selection for genes that repair and maintain our bodies when we are physically active.
Daniel E. Lieberman is a paleoanthropologist at Harvard University, where he is the Edwin M Lerner II Professor of Biological Sciences, and Professor in the Department of Human Evolutionary Biology. He is best known for his research on the evolution of the human head and the evolution of the human body.
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COMMENTARY
Daniel Lieberman, a Cultural Anthropologist from Harvard, makes the case that paleolithic hunter-gatherers Grandparents were helpful, in fact necessary to their families, and evolved to be active into old age. They did not evolve to sit in front of the TV, and modern men pay a penalty if they do.
INACTIVITY at ANY AGE is bad. If you put 20 year olds to bed, both weight and blood pressure go up. The book addresses a conundrum. Free radicals are bad. Exercise runs O2 through the mitochondria, which produces free radicals.
But EXERCISE REDUCES FREE RADICALS. A metaphor is introduced: you spill some tomato juice on the floor. But you clean it up, and the floor becomes cleaner than it was before. You exercise, the muscles suffer some microtears and injury. The REPAIR RESTORES the muscles to better than before, maybe with some extra mitochondria.
The Bodies MECHANISMS are MEANT TO BE USED. DIET is meant to supply the body energy and units for repair, EXERCISE is meant to use that energy, and keep the mechanism lubricated, and SLEEP is meant to allow for time to accomplish repair.
Sleep, Diet and Exercise can all be reconciled by recourse to Paleolithic man, whose activities imprinted our modern bodies.
Doctors Without Waiting Rooms 