Leona told to lose weight to be US success

How skinny do you have to be to be a top pop star? If you were to take your cue from the likes of Girls Aloud, you'd be stuck on a diet of fresh air and now the curse has struck none other than X Factor success story, Leona Lewis. She might be the first solo British female singer to have a number one single in the US for 21 years, but her advisors are suggesting that she lose some weight to see her star rise higher. Does having a small dress size equal big success?