Kelly Osbourne says the secret to her new slim figure is eating half an apple before bed.

The 23-year-old star - who has appeared at several New York Fashion Week events looking super-slender - has revealed her top diet tip to anyone looking to get in shape.

She said: "A trick I've learned is to eat just a little bit of something that has no carbs and no sugar in it before you go to sleep because it keeps your metabolism going. They say you should never eat before you go to bed, but I've found just having a tiny little snack - like half an apple or something like that - before you go to sleep really helps."

Kelly also credits her appearance on US TV talent show 'Dancing With The Stars' for changing her entire attitude to food and exercise.

She told America's Life and Style magazine: "I've completely changed the way I eat since doing 'Dancing with the Stars'."

Kelly - who is engaged to 20-year-old model Luke Worrall - also regularly does Pilates to stay in shape.

She said: "Pilates is amazing, my posture is so much better and I'm even starting to get muscles on my tummy - it's incredible."