Fergie stays fit by bringing her trainer on tour.

Although the Black Eye Peas singer performs punishing dance routines during her concerts she revealed she is so fanatical about keeping fit that she brings an exercise expert with her to ensure she stays in shape and even asks her dancers for tips.

She explained to People: "I brought my trainer on tour.

"I have the most amazing dancers. They do all these different things, a lot of squeezes, a lot of lunges. It's building what you want in the derrière - working for it!"

Fergie's obsession with exercise is not surprising as she has previously admitted she struggled to lose the 17lbs she gained for her role in the movie 'Nine' after filming finished.

She said: "I was eating my brains out. I ordered everything fried, full of fat and salty.

"It was a very gradual thing, getting back into it and finally letting a trainer train me. I didn't want to be told what to do, and I wasn't mentally ready to crack The Whip."