Beyonce Knowles tones her butt by walking up stairs.

The 'Halo' singer admits she was born with a "naturally good" rear end, but gives nature a helping hand by climbing flights of steps.

The 27-year-old singer explained: "I guess my butt is natural. But I go through stages like every woman. I like being curvy but sometimes I get curvy in the wrong places

"After New Year I do stairs - they are the best thing for butt cheeks. Every January I'll start working out. I'll do that for three months and then stop again!"

Even though she is proud of her body, Beyonce hates to be mentioned on lists of the world's sexiest women because she believes beauty is in the eye of the beholder.

She added: "Some people think one thing is beautiful, some think another is. When people say that I am 'most beautiful' or 'most sexy', it bothers me.

"I like fashion and I like to look good. I like to try at least, but everyone has their own opinion."