I’d say, “grow up.” That’s really a pretty disrespectful thing to say about someone you supposedly care about. I’ll bet the girl would be angry and hurt to know that he feels that way. How would he like it if the tables were turned, and she went around saying that he’s a really great bf, but she wishes he were packing more in his pants?
As others have said, even a Pamela Anderson body will age and sag, and there is always the possibility of disfigurement from cancer or a bad car crash or whatever. It’s what’s on the inside that counts, although there is nothing wrong with seeking a compatible partner whom you also find attractive. And if you yourself are a fitness freak, you will want a partner who is fit, simply because it would be a lifestyle issue and a priority that you share in common. Anyone who is dating someone they find unattractive to the point of being repulsive needs to stop dating that person and set them free to find someone who will love them just the way they are.
I knew a gal who got breast implants solely because her (now ex) husband wanted her to have bigger breasts. He was a total jack@$$, and he was abusive, self-centered, and obnoxious. He was not a kid, either; they were in their 30’s at the time. So after she got the boob-job, he wanted her to parade around in immodest outfits just so everyone could see how “hot” his wife was. So, against her own wishes (and conscience), she first allowed herself to undergo a violation of her body through the surgery, and then she ran around dressed like a tart just to please him (partially out of a fear of displeasing him, knowing that he could be abusive).

I’m just sorry that she didn’t realize sooner rather than later what a loser he was, before she married him in the first place. I certainly hope your friend isn’t cut out of the same cloth!