A lot of bad advice here (sorry but it's true). No, you should not do it either because she wants you to or because you're insecure because you THINK she wants you to. The only instance you should do this is for yourself because you want to.
Coming from a girl's point of view, don't do it because you think it's what she wants. You have to do these things for yourself, and if she truly is not happy with the way you look and wants you to change for her, then that's shallow and cruel. I love my partner, squashiness and all, and I would not expect him to change physically or in any other way for me because that's not being a decent human being. People have to want to change for themselves, and any party in a relationship who is attempting to influence you to change should raise some serious red flags.
I've been in a relationship for 10 years and I'm now 30. If anything has taught me anything, it's TALK TO EACH OTHER. The value of this advice cannot be underestimated. Tell her how it's making you feel and you feel like she wants you to look like these men.
Imagine if it were the other way around. How would she feel if you pointed out fit women on the TV all the time and said how attractive they are?