This 'American Idol' beauty has to work to flaunt her svelte figure.Carrie Underwood tells Extra that her tummy 'is an Underwood family tradition' and that her rear end 'starts going in and out so I have to work really hard to have it stay where it's supposed to be.' She says her diet has changed to exclude junk food and she tries to stay hydrated with both regular water and Vitamin Water.Carrie ...