I don't think you guys are quite grasping this as a mental disorder. Everybody has a desire to get in better shape. A disorder is when it gets blown so far out of proportion that it's a bad thing.
BDD, moreover, "Bigorexia" is not the desire to get HUGE. It is the complete and utter dissatisfaction with your physique and inability to perceive improvement. Imagine if despite all that you've ever done, you never (noticed that you've) made any progress. You'd go crazy, huh? You'd start doing crazy, crazy **** in attempt to make some gains. You'd become obsessed with adding a friggin' pound to the frame. I think it becomes a problem when you start putting this obsession above all other aspects of your life: family, friends, pleasure, God, school, work, health, and safety.