The physiology is made of the devatas. When it is healthy, activity is bliss. Like a vastu house or any vastu building. It is a structure built through Natural Law that creates harmony in every activity of your life.
With a vastu building there is an order-arrangement- to things both inside and outside of the building making specific areas for different activities. For example, the Northeast corner is the meditation room. If these areas were to be misarranged-put where they are not to be-then there would be disharmony for the people who own and are inside the building.
The same is true for the physiology. One needs to do specific things to keep healthy. If they do things that aren't good for them, then their physiology won't be healthy.