lou gent? i know he fought for super-middleweight and heavyweight titles although not both were world title fights
Butterbean Lowest: 280lbs Highest: 417½lbs I make that 137½lbs gained. EDIT: ****, world title. Missed that bit.
Another big one (not the answer, I know I know) is Guillermo Jones - 145 to 213. He's probably up near the top in terms of % gain though. Iran Barkley - 157 to 234 Biggest weight LOSS I think I know - Buster Mathis Sr started his career at 300 lbs and fought as low as 220.
What about Everett "Bigfoot" Martin? Martin went from 168 to some form of slobbishness in the 250s......... SR.BILLARDO
The biggest weight gain I can find for ANY fighter, is Carl Cancellor's 144 Lbs (296-440). I have no idea, if this is the all-time record (hh?).
Biggest weight LOSS?... well, that was actually going to be my next question, but hh beat me to it. I believe Mathis is the right answer - and by a pretty big margin too! I can't imagine anyone else coming even close to his 79½ lbs (300-220½). At least not if we limit our search to men who have fought for a title recognized by BoxRec.