I recently read this article and thought it was fascinating. Here’s the gist:
Our closest primate ancestors are notoriously lazy. They basically just eat and sleep all day (sounds ideal. I had aspirations to be Garfield when I was younger. . . and a beach bum so not sure how I got here). They do this to conserve energy.
So why would humans need to do something that expended more energy? The theory is that once we started migrating and needed to hunt for food, we began to evolve to adapt to exercise. Think about it, those that were able to hunt for food and were successful would pass on their genes that allowed them to do so. Over time, more and more of these people survived so we evolved to need exercise, at one time for food and survival but currently because it wards off chronic diseases.
Another interesting point is that we adapt to exercise so it becomes easier and burns less calories, at least for aerobic exercise. That’s the point of training. But back then, it was so massive amounts of calories weren’t needed to sustain the activity. This explains why aerobic exercise isn’t great for weight loss, because our bodies are generally lazy and always makes things easier to conserve energy. Putting on muscle is hard because it comes with an energy cost that at one point may have been the difference between life and death and survival is your bodies main driving force. This is why eating less calories and lifting are best for weight loss.