If a welterweight wanted to fight a HW, could he gain a lot of pounds and fight him?

[HitmanTommy]

Mikey jumped two weight classes and fought Spence for the first time at welterweight because he said he saw a weakness that he could exploit.

If a welterweight wanted to fight a heavyweight at heavyweight because he is confident he can beat him, would he be allowed to put on the pounds and give it a go?

[Ray*]

Well Andy Ruiz is a welterweight to be honest, and he just KTFO Joshua.

[Larry the boss]

yea, why not??

[megh50]

Nobuhiro Ishida moved from super welter to heavy. Also Toney moved from middle to heavy as did Roy Jones, so it's possible

[boliodogs]

Mikey didn't jump two weight classes. He was a very big lightweight who had to move up anyway. He had two good wins at 140 including a title win. Spence slaughtered him. If you are a natural welterweight you can gain lots of weight and fight a heavyweight but you would just be a very fat welterweight. Why would a welterweight want to do that? If the heavyweight is any good he will KO the fat bulked up welterweight. Every boxer has a best fighting weight. If yours is welterweight then fight there.

[_Rexy_]

James Toney started his career at Middleweight and finished as a Heavyweight. Nothing is stopping guys from doing it.

Ray Robinson almost won the Light-Heavyweight Championship of the world weighing only 157lbs. Had he won that fight, there's little doubt in my mind that he would have likely challenged for the Heavyweight title.

[SN!PER]

Depends how much money Bob Arum is willing to pay them.

[Dempsey19]

Jack Dempsey started his career at welterweight and became heavyweight champion of the world.

Super Welter Fitzsimmons won the heavyweight championship