Because his trainer, Firas Zahabi, doesn't want any extra bulk messing with St. Pierre's mechanics.
Following his one-eyed victory over the grappler who didn't grapple, the push for a potential "super fight" against middleweight champion Anderson Silva has lost some of its momentum in favor of another welterweight match-up against Strikeforce 170-pound champion Nick Diaz.
While logistically the fight may prove difficult to assemble, it's one that keeps St. Pierre at his natural weight and defending against a foul-mouthed fight monger like Diaz is a fight that sells itself.
And as Zahabi tells ESPN.com, the Canadian is in no "Rush" to pack on the pounds for greener pastures:
"He’ll be very small for a middleweight If I balloon him up to over 200 pounds, it won’t do any good. There’s a point where you can have too much muscle and it’s not a good thing. I think he’s got the maximum amount you can put on his body without it starting to be detrimental. If he goes up [to 185], I would recommend he stay the same size. You don’t want Georges to go in there bulked up and unable to perform in the mechanical way that he does. I’d probably push him up to 200 pounds for that fight. He still wouldn’t be as big as Anderson and it wouldn’t be natural, but it would be better. If you do get on Anderson Silva, having an extra pounds on you is a good extra 10 pounds."
St. Pierre has said he needs to undergo "a complete change of life" to take a fight at 185-pounds, which is where the Brazilian insisted on staying after cleaning out his division with a knockout win over Vitor Belfort back on Feb. 5.
Does a "St. Pierre vs Silva" super-fight require a catchweight for it to happen? Or will Yushin Okami make sure it never comes to fruition with an upset win in "Rio?"
And how many fans would rather see "St. Pierre vs. Diaz?"