I really wouldn't make this about the body characteristics of the girls he likes to watch. Personally I love the body of my girlfriend and especially her breasts, which are about your size I'm guessing, but her body is not the reason for why I'm in love with her.

There really is no point trying to change this behavior other than by telling him that you don't like it. You're either important enough to him for him to comply or you're not. I think it's such an easy and simple thing to do for you, I certainly wouldn't be with that person anymore if he keeps bothering you with it although you've brought it up as a problem.

But don't think he doesn't like your body because he prefers to look at women with other body characteristics, I'm sure that's not the case. At least from my own experience.