However, the actor and director, who is currently promoting legal thriller Michael Clayton at the Venice Film Festival, put an end to the rumours by revealing the real reason for his new appearance.
Clooney said that he has become an ardent devotee of a range of faddish fitness regimes and uses a variety of work-out methods to maintain his slender physique.
"We do a lot of aerobics, a lot of dance, there is a lot of jazz-ercise, the ab-master, there's the butt-blaster or whatever it's called. And also there is a lot of yoga," the Daily Mail quoted him, as stating at a press conference.
"And I have also just finished doing a movie where I did [American] football with a bunch of 21-year-olds which I highly recommend. That's going to keep anyone in shape," he added.
The revelation caused a round of applause from the press, prompting the actor to remark: "Thank you for asking that question".