Girls Aloud star has 'never dieted'
She said: "I've never dieted ... I actually have to be very conscious to make sure I eat. If I'm remotely run-down, tired or worried then I can drop weight overnight."
The owner of make-up range Dainty Doll explained that she eats large portions and suggested that her slim frame is inherited from her mother's side of the family who she described as "thin".
She explained that her hyperglycaemia means that she had to eat little and often to maintain her blood sugar levels.
The Sound of the Underground was the debut single from Girls Aloud and the group has subsequently achieved the most consecutive top ten singles of any band.