How can i get a flat stomach FAST?

I have a really thin torso and i don't have much fat on the top of my stomach but i have issues with my underbelly. It's not huge, but i want it to disappear as fast as possible. I heard that doing sit-ups will only make your underbelly hard and harder to lose. Are there any ways I can get a completely flat stomach and abs like this -- a href="http://images.askmen.com/galleries/model/alessandra-ambrosio/pictures/alessandra-ambrosio-picture-1.jpg" rel="nofollow"http://images.askmen.com/galleries/model…/a -- within a month?