Yeah, he's just 'eating right' and cleaned up his 'lifestyle.' That's all! Or, back in the real world, middle-age Chisora has suddenly become a KO artist in the last few years and it's one of the most suspect transformations in boxing. He'd always been a grinder who they pretended was a Povetkin like puncher, but he struggled to put proper opponents away cleanly. People forget how much leather he landed on Fury in the first fight without much effect. He couldn't hurt Haye. He got a very dodgy stoppage against Scott. And so on. Now he's a huge puncher apparently. KO'ing Browne in sparring is suspect as hell when you look back, it was hard to believe at the time due to Chisora's lack of devastating power in real fights til then. Now it makes sense. Sure, Pole and Price aren't the most robust but who else slept Pole and Takam like that except Wilder and Povektin respectively, and Price took a lot of punishment from Hammer and Thompson who are more in the power range Chisora used to occupy. You don't improve your punching power like this at middle-age by 'lifestyle' changes that don't involve PEDs.
Looks very rock solid at 260, considering a few years ago he looked flabby coming in at those higher weights. He's done alot of heavy resistance training with Haye. Because his physique looks huge.
Fighting 2 Glass Mandible opponents sure can make you look impressive fo' sho', a guy could make it to 50-0 with 50 KO's doing that!