From what I've read our body responds well to exercise. We exercise to hunt and forage, and our body responds by strengthening our bones and putting on muscle

From what I've read our body responds well to exercise. We exercise to hunt and forage, and our body responds by strengthening our bones and putting on muscle mass to support this. In summer we lose fat and in winter put on a little fat. more testosterone in the fall, maybe to mate and have a birth the following summer. If we stop exercising, are body figures out we have no available food and makes us listless so we conserve energy until food appears. We are in peril, so we put on fat and metabolize muscle to survive. Except in modern life our body thinks no excercise so more fat, less muscle, and less energy. So it is exercise that drives our body, not our body prompting exercise (excepting maybe fight or flight in brief bursts)