How many software developers do you know who say they don't "work" outside of the office, but then write code at home for personal projects? What is the definition of "work" then? What would happen if you start to let go of the concept of "work" as the bad thing, and expand the argument? I suggest we instead say using the same parts of your body and mind to the exclusion of the other parts is what is bad for you. Kno…
In my experience, the problem with overworking is not the activity itself. It's the mental state of doing a thing because of some sense of obligation, duty, or politicking/competition (or maybe threat, if you're doing it because you're anxious about job security).
Now that said, I totally agree that physically doing the same activity for endless hours every day is not going to be healthy -- including mental health. I think you're totally right to suggest balancing out job tasks with contrasted activities. It is good for your body, and keeps you from getting stuck in ruts mentally. As appealing as it sounds sometimes, I'm not just a brain in a jar. Using the muscles and talking to other humans is also important for being fully human.