@tchrist I don't think it's necessarily vigorous exercise that is needed, but I take your point. My worst period, healthwise, was when I was sedentary due to a knee injury, and I decided to put my energy into coding. I think I mentioned the outcome of that experiment.
@alphabet I suspect that's to keep them going while putting in that 4-7 hours of exercise. I couldn't ride my bike for three or four hours at a time without carbs.