To be honest, a teacher should be able to do something about it but it seems to look like they don't give a toss about you. (Not in a bad way towards you) I think, you should still tell another teacher about this, and say that ," My dad has already spoken to someone and this is not being dealt with, well I think it isn't being felt with." I'm sure from there, it would have been taken care of. If you want to lose weight, try to minimise the portion of food you have. (I'm not saying don't eat, I'm saying eat what you like in a reasonable portion). I feel sorry for you because I've been bullied and I cried myself to the teacher and that worked out. It doesn't matter if your are overweight, I'm not telling or agreeing to you. I'm just helping. You do what feels right.