Could a middleweight win the heavyweight championship of the world ?

[Le_Grand]

Like a modern day Fitzsimmons, weighing no more than 170.

Someone at 170lbs vs. Joshua, the current HW champion, who weighs 250lbs would not last more than 2-3 rounds. Perhaps the best MW could give Deontay Wilder a run for his money as he only weighs around 215 pounds but I'd still pick Wilder 99 times out of a 100. At this level of sport, a 45-80lb difference of almost pure muscle ... you simply don't go toe to toe.

[Dempsey19]

Someone at 170lbs vs. Joshua, the current HW champion, who weighs 250lbs would not last more than 2-3 rounds. Perhaps the best MW could give Deontay Wilder a run for his money as he only weighs around 215 pounds but I'd still pick Wilder 99 times out of a 100. At this level of sport, a 45-80lb difference of almost pure muscle ... you simply don't go toe to toe.

Bone weighs a lot. Taller people have bigger organs too.

[Le_Grand]

That’s besides the point. A significantly heavier body will still produce greater levels of force. Look at Mikey Garcia vs. Errol Spence or Amir Khan vs. Canelo as good examples of why these fight don’t happen. If moving up a weight class is a big challenge, imagine what fighting 3-4 weightclasses up means. No serious professional MW - by serious, I mean someone who wouldn’t be in it for the big payday associated with such a gimmick - would be willing to sign up for it. Zero.