I think there can be a few things going on with NB. But for most, it seems to have a lot with avoiding sexual things in some way - maybe altogether or maybe just parts of them. That can be the fear of having sex, the fear of being a sexual object, a dislike of perceived expectations, or something similar.
In some cases to me it seems to be about a type of reversion to a pre-pubescent body, where the person haven't really even accepted their adult body as part of their self-image. Maybe to a more idyllic childhood state or one that is percieved as safe.