OLEKSANDR USYK took aim at Andy Ruiz Jr as he hit out at “overweight” heavyweights.
The Ukrainian, 33, stepped up to the heavyweight division last year after becoming the first cruiserweight to hold all four major world titles.
Usyk piled on more than a stone in his quest to conquer boxing’s glamour division.
But the 33-year-old has resisted the urge to beef up his physique as he wants to remain “efficient”.
He looked lean when he weighed in at 215lbs (15st, 5lbs) for his heavyweight debut against Chazz Witherspoon.
Usyk is now waiting for his fight against Derek Chisora to be rescheduled after the initial date was axed due to the coronavirus pandemic.
During an interview on YouTube channel Usyk17, he said: “Some heavyweights are overweight and that prevents them from being efficient.
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“Why did they not lose weight? Because of laziness, I think.
“We can see that in the second bout of Anthony Joshua vs Andy Ruiz.
“Joshua lost five kilos and Ruiz put on seven kilos.
“In the first fight between them, Ruiz had his hand-speed and explosive force.
“Speaking about their bout second bout, I’ll use slang, I think that the refrigerator won finally.
“It’s so sad to say such a thing but it was a fault of Ruiz.
“I don’t want to be overweight of course. A few extra kilos can interfere with speed and mobility.
“So, I follow my diet. Though I rarely allow myself some sweets or having a meal in the evening sometimes.
“But however, my weight remains stable.”
Ruiz stunned the sporting world when he dethroned Anthony Joshua last summer.
But the 30-year-old came into the second bout at 20st 3lbs and admitted three months of partying had screwed his chances of creating more history.
The Mexican-American boxer has not been back in the ring since, but appears to have lost weight in recent snaps.