Anthony Joshua says Tyson Fury is jealous of his physique and has offered his heavyweight rival help in training.
WBA and WBO champion Fury called fellow Briton Joshua, 26, “useless” and said boxing was not just about “bodybuilding”.
Fury also predicted Joshua would be “knocked out” on Saturday by defending champion Charles Martin when they fight for the IBF title Fury was stripped of.
“They’re hating on my beach body,” said Olympic champion Joshua.
“If they want, I’ll give them some sessions. They can come train with me.”
Joshua overcame Dillian Whyte with a seventh-round stoppage in his last fight in December to claim the British heavyweight title.
The bout against American Martin, who beat Vyacheslav Glazkov for the vacant IBF belt in January, will be his 16th fight as a professional. He has won by knockout in the first 15.
Fury was stripped of the IBF title in December after he opted for a rematch against Wladimir Klitschko, rather than face mandatory challenger Glazkov.
Joshua added he had “no comments” on Fury’s physique.
“This is just how I am. There’s a lot of jealousy, a lot of negativity, so that’s why I shut it down and just focus on myself.
“I don’t search for their attention. I’m not worried if he backs me or not, because I’ll still handle my business. He’s not supposed to back me realistically, so I expect no different.”