How Much Exercise?

Posted 02/08/2011

I owe the details of this health tip to Dr. Joseph S. Alpert, the physician-editor of the American Journal of Medicine. Since a subscription to this highly respectable journal is, for non-physicians, $166 a year, I’ll assume it’s not regularly thrust through your mail slot and share his article with you.

Dr. Alpert begins by reviewing the now-familiar statistics for why regular daily exercise is good for you. You’ve heard much of this before: exercise prevents heart disease, slows cellular aging, drives down high blood pressure, improves circulation, boosts overall mood (you can actually reverse mild depression with exercise), and just generally improves your quality of life.

Most importantly, exercise reduces what statisticians call “all cause mortality,” a fancy way of saying if you exercise you’ll live longer.

Dr. Alpert wondered how and why regular exercise became so important for human beings. Let’s face it: not all mammals need to be particularly fit–do sloths or turtles spend their days working their bodies hard? Other animals, like lions and gazelles (or, on the Chicago landscape, squirrels and rats) had better stay buff or they’ll starve or be eaten.

Curious Dr. Alpert then considered exercise in terms of our genetic make-up. It turns out that archeological evidence proves our 21st century genetic structure–our genome–hasn’t changed much since the Paleolithic era. We’ve got the same genes as the men and women who emerged after the Ice Age 20,000 years ago. Maybe we’re taller and better looking, but they beat us hands down when it comes to survival skills.

It’s important to explore how our Paleolithic ancestors lived. After all, they must have done pretty well for themselves, since we’re all here today. We know for sure their culture evolved around small bands of hunter-gatherers living a very (very!) active lifestyle: hunting, gathering, running away from large animals to avoid being eaten, and running toward small ones in order to kill and eat them. Their DNA genetic structure was modeled by thousands of years of Darwinian natural selection to adapt to this active life.

With the strongest and fittest of their ancestors surviving and reproducing, 20,000 years later…us!

How does all this apply? It means our 21st century DNA structure actually requires an intensely active lifestyle. Statistics bear this out: We need physical activity in order to be healthy. We’re not genetically geared to tolerate the contemporary couch-potato, fast-food existence.

Right now, too many of us are dangerously thumbing our noses at the demands of our genes.

Just like 20,000 years ago, people in the fittest of our societies will thrive, while the least fit will not. We’re already seeing much evidence of this throughout the southern US, with disproportionately high rates of obesity, diabetes, early strokes, and early heart attacks.

In order to achieve maximum health, we need to include elements of the daily Paleolithic lifestyle into our own lives. This means regular daily exercise, lots of fruit and vegetables, assiduous avoidance of junky prepared foods and fast foods, and, of course, no smoking (can you picture a caveman lighting up a Marlboro?).

Knowing this, you might ask, “Well Dr. E, how often should I exercise?”

The answer is easy: Limit exercise to only those days you eat.