With her perfect porcelain skin, mane of long, dark hair and hourglass figure, Catherine Zeta-Jones has been the epitome of classic Hollywood glamour. That’s why fans were shocked when Catherine arrived at The Late Show With David Letterman on January 18 in a tight-fitting Herve Leger black dress that showed how her sexy curves having been replaced by jutting bones and thin limbs.

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The 40-year-old’s sudden slim-down comes just five weeks after she debuted in the Broadway musical A Little Night Music. The Oscar-winning actress (who was honored for her role in the film adaption of another musical, Chicago, in 2003) has been dancing since she was a child and began her acting career on the stage. She claims that her history tripping the light fantastic means that she snaps back into shape as soon as she puts her dancing shoes back on. “My muscles have memory from the time I danced, and it's quick for me to get back in shape, but I'm not fanatical,” Catherine has said in the past.