Alot of top bodybuilders havent got a clue about anything, nutrition or training.
They know alot about drugs though
He knew what it was, he was playing for the camera. Just like he was saying, "You gonna lose your girl too", whereas he alluding to a incident before where a out of shape dude had his hot girlfriend (complete with period thong up her ass, which was over tights), and he walked out because he saw Flex eying her.