Heavyweights often look like that. Not always: compare Holyfield – jumped up cruiserweight, cut like glass, to Lennox Lewis – who sometimes looked a bit doughy.
Once you’re past a certain weight you’re never going to be light on your feet or have much aerobic fitness, so at that point it can pay to put on the pounds. When you run out of puff at the end of a round you just lean on your opponent, who then has to support your weight as well as his.
… or at least it gives you that option. Despite looking like he’s come straight from a pie-eating contest Fury didn’t box like that last night, but if Wilder had been more aggressive Fury could have gone that way.