Well from my own experience, I'd have to say no. Once we learn that Barbie's body is blown out of proportion, therefore literally impossible to achieve, we stop seeing barbie as "physical role model" but a chunk of Manufactured in China plastic. I honestly think it doesn't hold much of an influence at all... Even if you are somehow influenced (negatively) during your childhood, every girl grows out of it eventually.
Media has it's share of influence on the general female population, but there is a good balance (in my opinion). You know how you hear all the model/fashion industry bashing and how they set the standards for the perfect body, leading to anorexia, bulimia etc... On the other side you have a whole flock of people raising awareness about the dangers of eating disorders. It always balances out. So even if the expectations the media places on their female audience are ridiculous, freedom of speech will inevitably lure the masses to point that out!