‘The Notorious’, a former two-weight world champion, is expected to return to the octagon later this year and has promised to fight again for a world title despite losing his last two bouts.

The 33-year-old is thought to be cutting back his weight to 155lb, around 70kg, so he can fight at welterweight level, but recent training pictures show McGregor looking ripped and in great shape.

He posted a video of a ‘Proper Twelve’ challenge – 12 weighted pull-ups for ‘St Practice Day’, in reference to his Proper Whiskey business and upcoming Irish celebration St Patrick’s Day on Thursday March 17.

   

Stunned fans have hailed Conor McGregor’s body transformation as he packs on the muscle

Fans reacted with incredulity to his gains, with one questioning if he still has enough speed

One fan said he would nickname him ‘McJacked’, while another joked McGregor could challenge to be ‘heavyweight champ’ despite his world titles coming at featherweight or lightweight.

Another added: ‘This dude definitely isn’t making 155lb any time soon’, with a third posting: ‘Conor is looking much bigger than usual, think his next fight will be at 170’.

A fan of the sport said: ‘Will those arms make 155? They look crazy swoll,’ while one quipped: ‘Conor BigGregor’.

Others questioned his mobility given the muscle mass gained, with a sixth saying: ‘Lookin like a tank, hope you still got the speed though’ and another echoing those thoughts, tweeting: ‘Too much muscle to be fast I think’.

Potential opponent Jake Paul insisted he was happy to drop down to fight McGregor at 175lb

Although the date and opponent when he returns has not yet been confirmed, McGregor is reportedly keen to face the winner of the Justin Gaethje vs Charles Oliveira fight in May, with a mooted return in early July.

An eye-catching bout with YouTuber-turned-boxer Jake Paul could also be on the cards, with American Paul recently offering to drop down to 175lb – closer to McGregor’s weight – to secure a fight.

Paul, 25, has weighed in as high as 192lb in his fledgling five-bout career (5-0), but has insisted he is happy to fight at light-heavyweight.

McGregor has fought at 170lb, winning against Nate Diaz and Donald Cerrone, and could be around that weight with his recent muscle gains.

Paul tweeted: ‘(UFC chief) Dana White is begging for Diaz and Conor to fight for a third time. They have fought at 170lb in both their fights. I will fight Conor at 175lb, no problem. Stop making excuses p****es.’