Anthony Joshua faces Andy Ruiz Jr on Saturday, December 7 for the unified heavyweight world titles, and a recent photo has shown just how much muscle mass he has lost in the build up.

In preparation for this rematch, AJ has been working hard getting himself in shape to ensure what happened in June doesn’t happen again.

The Brit was floored four times in a seventh-round stoppage defeat to Ruiz in the US and is keen for redemption this time around in Saudi Arabia.

AJ took to Instagram and Snapchat to show off his new lean figure ahead of the fight and fans are clearly noticing the difference.

Before, he was a sporting a much beefier look, whereas he now appears to be looking visibly trimmer in muscle mass suggesting a potential change in fighting technique.

With this new build, it’s likely that AJ has been forced to trim out his usual diet of 4,000 and 5,000 calories per day with the basis of his diet including five eggs in the morning, two chicken breasts for lunch and two fillet steaks for dinner.

Fans are convinced that AJ now looks like 'a boxer instead of a bodybuilder model', suggesting that this body transformation is a good thing.

Followers were quick in noticing the transformation with a few comments on his Instagram post reading: “Looks a little smaller, hope it helps you”, “Holy s*** you got smaller,” and “Look how lean he’s looking now. He’s got the W for sure this time around.”

The loss to Ruiz Jr back in June may have been a contributing factor to the reason that AJ has slimmed down as he has since claimed, when speaking as part of Matchroom Boxing’s JD Access All Areas series: “It’s good that I lost because all the sparring partners have come out now. No one wanted to spar me before.”

Having experienced defeat for the first time professionally in June, AJ has insisted the shock result can not be repeated, and stated: “If you put me and Ruiz in a machine, nine times out of ten I should beat him.”