I’ve thought about this. Or at least something like that.
When reading dune there’s a class of women who can control their biochemistry in such a way that they can eg prolong lifespan, or anything else within the realm of feasible biochemistry.
Here I was like: how does the nervous system function in that way? How could signals from the mind control the behavior of molecules?
The mind cannot itself feel pain, similarly the mind has sensory limits within the body. As argued in a book called the body a guide for occupants: cancer is a very good example of a disease that our nervous system should be able to detect but for whatever reason we don’t, probably because cancer is something we can only now treat.
Not all of the body can be made legible to the mind.
Although maybe a better question: why don’t we have a dedicated organ that can sample blood with laboratory like precision and make anomalies available to the conscious mind beyond whatever faculties we currently have?
PS
One thing that definitely should be within the realm of conscious control: body fat. There are ways of forcing the body to metabolize more fat for energy and the biggest problem is managing excess heart (easily becomes lethal). But this could be super useful in cold climates. Imagine being able to literally burn body fat to stay warm? The amount of heat that can be released is enormous. Nowadays most of us could probably afford the otherwise superfluous expenditure of body fat (beyond essential functions).