There are other fucking things to worry about than whether some hunk finds you disgusting because you feel your ass is too big, or you have some pooch on your belly which guys don't even notice in the first place. Guys do tend to look at personality as well, you know. And if you're this skinny chick who's a complete airhead, you'll attract certain guys. If you're a skinny smart chick, you'll attract different guys. If you're a fat airhead, you'll attract a third type of guys. And if you are a fat smart girl, there are guys for you, too.
If you are so worried about your looks, then why in the hell did you allow yourself to get that way in the first place? And how do you know that the hunk you're so interested in getting to notice you isn't, in fact, gay?
I find that girls who are comfortable with themselves as they are, whether be it skinny or fat, are a LOT more fun to hang out with. These are the girls who aren't checking the mirror in their compact every five minutes to make sure their makeup hasn't smudged or if an eyelash is out of place. People come in all shapes and sizes, and you might as well just get comfortable with yourself.
A girl with a good personality is far more attractive than any girl made up at the most expensive salons.