Should I say something? Really need advice!?

My bf use to be 400 lbs. He lost over 200 lbs, but recently gained a little weight. He is no where near the weight he once was, yet his one "good" friend keeps making comments and little digs. What really pisses me off is that this guy is at least 80 lbs bigger than my bf. I think he's doing it to make himself feel better about his own weight. It bothers my bf, but he never says anything. Should I stand up for him, or just continue to bite my tongue? My bf is confrontational and doesn't like to argue with his friends, so I'm afraid if I say something, it will start a fight between them. I really don't want to cause a rift between them. I must admit, it's getting really hard to keep quiet about it.
Should I say something? Really need advice!?
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