MMA fighters are built like wrestlers, not bodybuilders. A wrestler has to have nlow bodyfat because of weight classes. Lower bodyfat=more functional mass. When fighting an opponent of equal weight and skill, the amount of functional mass comes into play, in other words he can out muscle an opponent in a technique stalemate. Have you seen the early UFCs. Not a lot of great physiques. Ken Shamrock was a fighter first, the mass he has is functional. A true pro-body builder does not have functional mass, they are just slabs of meat.