I am not an expert on what happens in the female changing rooms, although I do have an friend (young and attractive) who has told me a number of time that masculine looking women with short hair in the changing rooms (I presume lesbians) look at her beyond what is normal when she gets changed, and is in the shower and so on.
I have nothing against lesbians at all. In fact when I was a student I would sometimes make a menage in my apartment in Paris on occasion. (Whether that kind on intermingling is called lesbian I am not sure). But the point is, it depends on the appropriateness of the environment and occasion. If I go to a gay club, of course I woudl expect many man to express in interest towards me (and I could not rightly complain about that). But in a gym, this is supposed to be for exercise. The men who go there wearing tight short pants, tight white T shirts, and then the spend a very long time in the changing rooms making an eye towards men, or sitting with a towel open to attract you and then they give you a "gay" smile - that is what I find very undesirable to see.
Other readers here who go to the gym will confirm this. But do not misinterpret me - I have nothing against these people, just I wish they do not do it in a gym which I innocently joined.