Kelly Clarkson on Weight: “I’ve Never Felt Uncomfortable”

Kelly Clarkson admits her size fluctuates in the September issue of Self mag. "My happy weight changes," the American Idol champ says. "Sometimes I eat more; sometimes I play more. I'll be different sizes all the time."

See pics of Idols who have lost or gained weight.

Clarkson, 27, says she doesn't care though. (In June, she admitted she was tired of hearing "the fat joke" because she'd accepted her curves.)

"When people talk about my weight, I'm like, 'You seem to have a problem with it; I don't," she explains. "I'm fine! I've never felt uncomfortable on the red carpet or anything."

Check out pics of scary skinny stars.

The singer tells the mag she's been working out with CrossFit, a strength training and cardio program used by police academies and military special operations, according to its Web site.

"I love it! It's like boot camp," she says. "You never work out more than 35 minutes, but it's so intense. You do things like box jumps, then 50 sit-ups, then 50 squats and then running.

See more photos of stars working out.

"Me, my backup singers and my hair-and-makeup girl do it together. They laugh at me, because most of the time they're like, 'Oh, my God, I don't want to go,' and I'm the one saying, 'I'm ready!'" she goes on. "It makes me feel like GI Jane. It's very empowering. I feel like I can whup a–! And in my shows, everybody has noticed. They're like, 'Dude, you have 100 percent more energy!'"

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