How do you all deal with other women who talk negatively about their appearance?

A lot of my girl friends do this and it's heart-breaking. The first few times I'll respond with something like, "no, you look great!" But it gets annoying and draining after a while, so I just stop acknowledging the negative comments all together. I know that they're fishing for compliments in because they are not confident in themselves and that this is obviously their personal problem and there's only so much I can do, but I'd still like advice. How can I be there for folks that talk negatively about themselves without always necessarily having to always remind them they're beautiful? I find a lot of times when I say this, it'll go through one ear and out the other. Sometimes I'll try educating them about how we set unrealistic expectations about ourselves due to media portrayals of what's beautiful and that's been a bit more effective, but I'd love to hear other strategies.