Nate is what you would call an "ectomorph" build. The term ecto-meso-endo -morphs is a bit unscientific but has some application.
Much like a basketball player. You don't really see many brick-fucking house dudes on the court. Sure there's some guys who play PF/C that might be thicker and even some guards like Felton/Barrea, etc. But the majority of basketball players are built like WRs/CBs in the NFL,
and Nate Diaz is basically an unathletic (by comparison to NBA/NFL) version of that. He's like a Lonzo Ball type build. Nate probably does not lift weights at all, just boxes and does BJJ / MMA training. So here is the long response to a really dumb question.