My understanding is that control of your own body is through your mental model of your body, not directly asking individual muscles to contract. (This is why people get phantom limb issues after amputation.)

In that context, I think it makes sense to include body in the list of things not under your control (you can only control the actions you ask your body to do, not what your body actually does or the per-muscle detail of how it does it).

He definitely is referring more to things like disabilities and diseases, not necessarily fitness and beauty.

But to his point more generally: if you can control it, do so. If you cannot, don't pretend that you can.