The Girls Aloud singer is famed for her tiny frame but she insists no matter how much she eats she can't pile on the pounds and is often envious of bandmate Kimberley Walsh's curvy figure.
She said: "I'd say to Kimberley that I wish I could put weight on. I look at her curves and I'm there stuffing my face but it just doesn't work. I used to be a dancer so I have muscle memory, I can literally carry bags of food shopping and my arms go muscly. I can't bear it. I want them to be smoother and more womanly."
However, Nicola is generally happy with her appearance and has learnt to accept what she looks like.
The red-headed star told Look magazine: "It's healthier if you think optimistically because there are always people out there who are in a far worse situation than you are. If you're born with pale skin, you're born with pal skin just as if you're born with olive skin. Whatever shape you are, colour you or size you are, it's just what you're born with."