Though the model, 32, hasn't addressed the pregnancy rumors herself, a source tells TMZ they are "100 percent false."
And on Wednesday, Keibler, who is vacationing in Como, Italy, with Clooney, 51, at his famed estate, uploaded a photo of herself in the gym. With a dumbbell in hand, the model shows off her sexy, sweaty six-pack abs in a white sports bra and black yoga pants.
To get her bangin' bod, Keibler constantly changes her workout routine. "I go to Barry's Bootcamp, I go to Physique 57 -- every week is different for me," she told Us Weekly earlier this year. "Sometimes I'll go to Barry's three times a week because it fits into my schedule better, and sometimes I'll work out with a trainer five times a week."
Keibler, a former Baltimore Ravens cheerleader, has always been athletic. "I started dancing and playing sports at a young age, and then I got into cheerleading and I've always had that," she told Us. "But even at 15, I was going to the gym. I've just always been conscious of being healthy and I'm really very balanced. I like to eat a lot so I have to work out a lot to balance it out."
Keep clicking to see pics of Stacy's enviable physique ...