Maybe this belongs in the "women hate" thread, but I got stuck in a conversation the other day with a female jiu jitsu acquaintance who was talking about how her (male) coach told her to lose weight. Girlfriend did have a few extra pounds on her. She took it as sexism. The (female) coach piped in and said he really shouldn't say that because women get eating disorders from stuff like that.
I tried to be as gentle as possible when I explained that, while men could stand to be a little bit more sensitive because men and women are different, the fact of the matter is, you're in a male-dominated sport and you are dealing with men. The man who tells you to lose a few pounds isn't doing that to hurt your feelings or call you fat, it's because he thinks you'd probably do a lot better in a close-contact sport with narrower limbs and the occasional putting pressure on your neck to do inversions.
The bigger girls, hands down, have more problems when their opponent has them on the ground, and especially if their opponent is standing, because, if you're going to employ some sort of defense with your legs, less weight makes your mobility better, you're more nimble (and you need that if you train with guys), and let's face it, BJJ is an endurance sport.
You can't get mad if you ask how to get better, you're surrounded by people who are better, and they're all thinner than you, and someone you trust as an expert ran the numbers and gave you advice based on years of observation. Even the bigger new guys will tell you they want to cut weight. So, yeah, weight IS a measurement that is correlated with fitness and goodness in this sport.
And this is why I like training with men, and I let them know how grateful I am that they put up with someone like me every chance I get.