It is only common sense. But of course I am now just starting to understand how it works. It is not just eating healthy foods but also exercise that is needed to keep the machine running without too much disturbance.
Just motion alone is very therapeutic. Dragging around through daily activities or simply remaining sedentary and thinking so many things is not a good program. Maybe for a meditative yogi sitting still and not moving is okay but not for an aspiring devotee.
When a child walks or moves he is full of bounce. Walking is not just dragging from one place to another. It is a full body motion. If we practice like this even if the tendency is to drag around begrudgingly but instead practice joyful movement our spirits are lifted. Oxygen flows throughout the blood stream and the brain and thinking of Lord Krishna is easier.
Why do we move our bodies anyway? Because we are forced to? We have to or something bad will happen. Out of fear. Out of lust or greed for something. Do we always have to have some material reason to even move?
There is hearing and chanting and there is also dancing. In the spiritual world all talking is song and all moving is dancing. Every movement can be a joyful expression. This is an important part of practicing devotional life. Simply moving the body for Lord Krishna.
If Srila Prabhupada had not made the effort to reach out to us with message of Godhead we would know nothing at all.