Tyson Fury has mocked Wladimir Klitschko, telling him he was beaten by "a fat man" in their first encounter.
Manchester's Fury, 27, caused a big upset by outpointing 40-year-old Klitschko in Dusseldorf last November.
The rematch for Fury's WBA and WBO heavyweight titles will take place at the Manchester Arena on 9 July.
"Shame on you, you let a fat man beat you," said the undefeated Fury, after stripping his shirt off and clutching his stomach at a news conference.
"I don't even live an athlete's lifestyle. It's a disgrace to call me an athlete.
"Wladimir lives a strict lifestyle, but what's the point in being professional for all those years if you can't beat a fat man?
"I could beat Wladimir if I was 30st and fat as a pig. I don't need to turn up in shape."
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Fury, who is unbeaten in 25 professional fights, added he was "hating every second" of being a world champion.
"Boxing doesn't mean a lot to me," he said. "If it did, I wouldn't have eaten all the pies, drunk every pint of beer in Lancashire and gone into camp four stone overweight.
"I wish I wasn't a boxer. I hate every second of training and I hate speaking to all you idiots. I'd rather be at home with the kids watching television and eating sweets.
"But I'm just too good at it to stop. It's easy money, knocking over a few bums.
"I'm not motivated for the fight. I hope he winds the clock back and puts me into next week. Then I can retire, get fat and go on loads of holidays."
Klitschko, who is attempting to become a three-time heavyweight world champion, criticised his rival's controversial views and swore at him.
"I don't look up to Tyson Fury," said the Ukrainian, who had not lost for 11 years before Fury beat him and whose last fight in Britain was against American Monte Barrett in 2000.
"What comes out of his mouth is not right. I will knock him out."
But Fury added: "Last time he got beaten fair and square in his own backyard. He landed about four shots in 12 rounds.
"If a so-called super champion can't land on a big, fat, lazy Gypsy with a loud mouth, what kind of a super champion is he?
"I'm going to knock him out inside a round, just to show how bad he really is. No 40-year-old can beat Tyson Fury."