Try again. How about the fact that it matters less what men look like, and therefore they get criticized less? (That and the fact that if a man expresses his preferences for other men's aesthetics he runs the possibility of having his manhood challenged, by others or himself ... ah phobia.)
As for women being criticized for being too skinny, sometimes it is a jealousy thing, because for most women it is an unattainable standard. Few women naturally have a body type that is encouraged by media employers, so many women starve themselves and become too skinny for their frames because they are told that's what people want to see. One reason women criticize women who starve themselves is because we do sometimes see it as a form of betrayal - they are telling us that it's not okay to look like ourselves, and that we should change ourselves in an unhealthy manner in order to become more like the "ideal". Why do we get "catty"? Because we're ing hungry.
Men can be "too skinny" or have a few extra pounds, wrinkles, gray hair, etc - in other words, it's much more okay for men to look however they naturally look. I'm not saying that men do not have certain social standards of beauty, but they are FAR less stringent than those for women.