LONDON: Kelly Clarkson isn't worried about her weight. The 'My Life Would Suck Without You' singer is often criticised for her fluctuating figure but she insists she doesn't let it bother her.

She said: "My happy weight changes. Sometimes I eat more, sometimes I play more. I'll be different sizes all the time.

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

The curvaceous star - who won the first series of 'American Idol' - also revealed she has been working out with CrossFit, a strength training and cardio programme used by police academies and military special operations.

She told Self magazine: "I love it! It's like boot camp. 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.

"Me, my back-up singers and my hair-and-make-up 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!'

"It makes me feel like GI Jane. It's very empowering. And in my shows, everybody has noticed. They're like, 'Dude, you have 100 per cent more energy!' "