Why is exercise healthy?

It has been said that exercise is the closest thing there is to a miracle cure. “All the evidence suggests small amounts of regular exercise (five times a week for 30 minutes each time for adults) brings dramatic benefits.” But why is it so awesome? In a really general sense? What makes it such a wonder drug?

Exercising at the right intensity +The right intensity being the Goldilocks zone: enough to provoke adaption, not enough to injure. is biologically “normalizing,” pushing systems to work the way they are supposed to work. Biology is all about clever homeostatic mechanisms that nudge tissue state back to average. Those systems all rely on negative feedback loops based on molecular signalling (hormonal, neurological, etc), and exercise produces a lot of stimulation … raw “data” to feed into the negative feedback loops, which is normalizing.

It’s not a universal principle, and exercise cannot normalize everything. +Many specific pathological processes are a freight train that will not be stopped by exercise. Consider a blatant example like a tumor, or something a little less obvious like multiple sclerosis. But it does stimulate an incredible array of adaptive and homeostatic mechanisms — way more than any other kind of treatment.