“Last year, Ashley and a large team of scientists conducted an elaborate experiment on the effects of exercise on the mammalian body. In one test, Ashley put rats on tiny treadmills, worked them out for weeks, and cut into them to investigate how their organs and vessels responded to the workout compared to a control group of more sedentary rodents. The results were spectacular. Exercise transformed just about every tissue and molecular system that Ashley and his co-authors studied—not just the muscles and heart, but also the liver, adrenal glands, fat, and immune system.

When I asked Ashley if it was possible to design a drug that mimicked the observed effects of exercise, he was emphatic that, no, this was not possible. The benefits of exercise seem too broad for any one therapy to mimic. To a best approximation, aerobic fitness and weight-training seem to increase our metabolism, improve mitochondrial function, fortify our immune system, reduce inflammation, improve tissue-specific adaptations, and protect against disease.”

https://www.derekthompson.org/p/the-sunday-morning-post-why-exercise