Exercise appears to spark a whole-body anti-aging cascade, and scientists have now mapped out how it happens—and how a simple oral compound can mimic it. By following volunteers through rest, intense workouts, and endurance training, researchers found that the kidneys act as the hidden command center, flooding the body with a metabolite called betaine that restores balance, rejuvenates immune cells, and cools inflammation. Even more striking, giving betaine on its own reproduced many benefits of long-term training, from sharper cognition to calmer inflammation.