what illness does he have?
Apparently he has some sort of heredity illness that is only found mostly in Romani gypsies! His Dad mentioned it in a old interview, for many years they just thought he had normal ache! (But his Dad knew there was something not normal, because he was constantly throwing up during training sessions).
I actually thought he looked the better when he stood his ground in the middle of the ring and traded; he had the longer reach and neither of them had much power. He could have won the fight if he didn't have such a poor gameplan, which was basically run, spoil, flick some jabs and expect hometown judging to hand him the title. Parker was a poor mans Alex Leapai in there and he was smothering his own work, but Fury's gameplan didnt involve landing punches so he came up short.
Health had zero to do with it, it was just a bad gameplan.
He needs to acquire his man strength! (He is a very good boxer, but he lacks bruit strength! This is probably due to his illness)...
what illness does he have?
Would he be able to pivot, move, glide like he does if he bulked up to add power ? Doubtful. Fluff Fists is who he is and unfortunately in this era I don't see him winning a belt, title or the 'world title'
Which is besides the point anyway, he's already stated he's in the best shape of his career and has no excuses. Dude has belief, likely over confidence, the Furry's spar some real lousy piss poor sparring partners.