Former world champion Roy Jones Jr has questioned the need for Andy Ruiz Jr's extreme weight loss regime under new trainer Abel Sanchez, saying it could hurt his ability to take a punch from Joseph Parker in their world title fight next month.

Jones Jr, a 47-year-old American who made history when he became the first boxer to win a heavyweight title after starting his professional career as a light middleweight, knows a thing or two about gaining and losing weight.

He was a world champion in four different weight divisions and was considered by some as the best pound for pound fighter ever. He finished his career with a 54-8 record, and was named in the boxing hall of fame in 2003. He retired in 2011.

"When you take weight away from a guy, a lot of times you see bad things happen," Jones Jr said after a press conference in a build-up to the Sergey Kovalev v Andre Ward world light heavyweight title fight in Las Vegas. "To me, when I put all the weight on and won the heavyweight title, and went back down in weight, I never would've got knocked out if it hadn't been for that, I don't think.


"You see Chris Byrd when he was fighting at heavyweight all those years, as soon as he dropped down to light heavyweight, one fight, out he went.

"Losing weight has been proven to take away a guy's ability to take a punch, so you have to be very careful when you take weight off a guy, especially a guy who's used to being that big.

"So for Joseph Parker, he should hope that's the case. For me, I'm the kind of guy who thinks if there's nothing wrong, don't fix it."

Ruiz Jr is expecting to weight about 111kg for his fight at the Vector Arena on December 10, but has fought at more than 140kg before. He has lost more than 20kg training with Sanchez at altitude in California.

Other observers say Ruiz Jr's punching power could be compromised by the weight loss, but Jones Jr believes the Mexican's ability to take a punch from the powerful Parker would be more relevant.

"For a big guy to have that quick a hands? It's a sight to see, so had it been me, I wouldn't have taken much weight off him.

"I may have tried to get a little flab off him, trim him up just a little bit, but not take the weight away from him because that weight could've been enhancing his ability to take a punch and he has really quick hands, so most guys aren't going hit him clean because of his quick hands, you understand me?

"You got to be really careful not to over do it. A lot of guys go 'I'm going to go to Abel' because they want to get in shape, which he does get them in immaculate shape, but everyone don't need the same thing."

* Patrick McKendry travelled to Las Vegas with assistance from Duco Events.