You have to look at your own body and try and be objective. Everyone has a different shape, just like everyone has a different nose shape. No amount of dieting will make ME look like that cos I have massive legs and no waist! You can't alter your intrinsic body shape, but if you want to be a model, you need to be a certain height (5'8'' plus) and you need be thin so that clothes drape well on you. You need to have a "blank canvas" type face. I am sure you will have seen America's next top model, and the UK and Oz equivalent. You will see from that that the girls are often not "pretty" but they have wide-spaced eyes, good teeth and skin, and strong hair. Most of all they will have good personalities, be go-getting and hard-working, and not afraid to be an actor.
You should look to your whole self rather than your specific body parts.