Thanks to NomadMaker identifying the author as Poul Anderson, I believe that a strong candidate for an answer is the novella "[The Sensitive Man][1]", first published in 1954 in *Fantastic Universe*.

The story takes place in the far-future year of 2009(!), and is set in Poul's "[Psychotechnic League][2]" future history. A summary at [wikipedia][3] describes the plot well:

> Michael Tighe of the Psychotechnic Institute has been kidnapped by
> Thomas Bancroft, a politician with ties to an authoritarian movement
> called the Actionists. Tighe's adopted son, Simon Delgatty, sets out
> to find him, but is himself captured by Bancroft and taken to his base
> on an island off the coast of Mexico. In the course of raising
> Delgatty, Tighe has trained him to exert conscious control over what
> are normally subconscious and autonomic brain functions. This allows
> Delgatty to speed up or slow down his metabolism at will, and also
> allows him to tell what other people are thinking by listening to them
> subvocalize their thoughts.

As the question noted, the protagonist, Delgatty,was trained to take advantage of "the relationship between the conscious, subconscious and involuntary minds" to have a perfect memory, have superhuman physical abilities, and to apparently read people's minds. In fact, however this is due to:

> Most people sub-vocalize their surface thoughts. With a little
> practice a person who can hear those vibrations can learn to interpret
> them.

His abilities take a toll on his body though.

> "There are sound biological reasons why man's mind is so divided and
> plenty of penalties attached to a case like mine. It'll take me a
> couple of months to get back in shape after this bout. I'm due for a
> good old-fashioned nervous breakdown and while it won't last long it
> won't be much fun while it does last."

The complete story is available at [Project Gutenberg][4].


  [1]: https://www.isfdb.org/cgi-bin/title.cgi?58315
  [2]: https://en.wikipedia.org/wiki/The_Psychotechnic_League
  [3]: https://en.wikipedia.org/wiki/The_Sensitive_Man
  [4]: https://www.gutenberg.org/files/31501/31501-h/31501-h.htm