Rob McElhenney’s extreme weight gain and how he got ripped for It's Always Sunny joke

Rob McElhenney has been through some insane body transformations in the name of comedy.

Rob, 46, known for his role of Mac in the hit sitcom It's Always Sunny in Philadelphia, gained 60 pounds over the course of seven months because the writers thought a fat Mac would be funny.

This massive weight gain took place between the sixth and seventh season and McElhenney - who shared his neurological disorder diagnosis this week - was taking down four 1,000 calorie meals a day to pack on the pounds.

The writers then thought it would be funny if the character came back completely ripped, so that's exactly what McElhenney did.

Rob McElhenney, left, and Glenn Howerton, right, pose shirtless showcasing their fit bodies on their hit TV series It's Always Sunny in Philadelphia (robmcelhenney/Instagram)

Actor Rob McElhenney flexes his fit body in shirtless beach photo posted on his Instagram in 2020 at the leak of his fitness journey (robmcelhenney/Instagram)

In a 2020 Men's Health interview, McElhenney shared the truth behind his insane body transformation. In the video the star reads off a Tweet with photos of his body saying Rob has more "dedication to the joke" than anything than she has to anything in her life, to which he admits that he doesn't - he has dedication to the paycheck.

The actor jokingly says: "If you can find a studio who's willing to pay you what they pay me to make Sunny, you will have a lot more dedication than you think."

Actor Rob McElhenney on set as Mac showing off his abs after insane weight loss transformation in the TV series it's Always Sunny in Philadelphia (FX)

In the video, he playfully breaks down how anyone could get a jacked body like he did.

He says that it's quite simple saying: "Anyone on the planet can do this. First things first, if you have a job, like a 9 to 5 job, - quit that. Now do you like food? Forget about that because you're never gonna enjoy anything you eat. Alcohol? Sorry that's out."

He then tells viewers to get their personal chef to make a lot of chicken breast, make sure you have the personal trainer from Magic Mike take you to the gym at least twice a day, and abandon your family and kids because they'll take time away from getting jacked.

Rob McElhenney eating on set as his character Mac in It's Always Sunny in Philadelphia at the his heaviest after gaining weight for a joke on the show (FX)

The actor also reads off a comment from an Instagram post of him shirtless on a boat, that wrote: "WHERE ARE THE ABS ROB?!?" to which he wittily responds: "I'm going to give you a little lesson in biology - the abs are always there. They're in there, they're just behind a bunch of tacos and tequila. I was enjoying myself on vacation."

He goes on to joke that he could easily get his ripped six-pack back any time, all it takes is 'three to four months of starving myself.'