How Jai Courtney banned beer and carbs to buff up for his nude scenes

YOU know that moment when a Hollywood star beefs up and suddenly gets super hot? It’s just happened to Aussie actor Jai Courtney — and there’s a good reason why.

JAI Courtney swore off beer and carbs on learning he was to appear naked in Terminator: Genisys.

“There’s an expectation you will look your best,’’ said the Aussie actor from LA, where he has just finished shooting the reboot with Arnold Schwarzenegger and Emilia Clarke.

“I think it’s easier for some people than others because genetics come into play. And it certainly doesn’t get any easier as you get a little older.

“I really have to watch it because eating good food is something I am passionate about. Eating a balanced, nutritionally-focused diet is tough. So what I will tend to do it really knuckle down for periods of time when it really has to count.”

Courtney, 28, will next be seen on screen opposite Joel Edgerton and veteran British actor Tom Wilkinson in homegrown crime drama Felony, which opens in cinemas on Thursday.

JAI COURTNEY: A name you need to know

If you’ve got it ... Jai Courtney strips down to his Y-fronts. Pic supplied.

He scored the role of John Connor’s father and resistance leader Kyle Reese after the producers of young adult franchise Divergent rearranged his filming commitments on the upcoming sequel Insurgent to accommodate his Terminator production schedule.

The knowledge that he would be shirtless for a good deal of screen time — and even butt naked on occasion — kept Courtney focused on his diet and training program.

Suited up ... Jai Courtney (left) and Tom Wilkinson in a scene from Felony.

“It’s always a little nerve wracking,’’ says the actor, who also stripped for Spartacus.

“But you just get the job done, don’t you.

“Some people have a trickier time of it than others. It doesn’t get easier second time around, but I guess I don’t struggle with it too much.”

Just as well, since Courtney was recently hired as the male face of Bonds, a role that requires him to regularly strip down to his Y-fronts.

The right to bare arms ... Jai Courtney in a scene from film I, Frankenstein.