It really doesn't matter how much you weigh like every one has said its how strong your diaghram (sp?) is. I have been singing for 12 years and im overwieght and people say that i have a really great voice (even though i still don't think that i do. convidence is not my thing. i get scared alot. lol) but i do think that when you do tone down a little ( i still don't think wight has anything to do with it!!!) your vocal range gets a little better. like you can get the notes that you couldn't before and you can hold notes longer. every body has their range and has their own personal style on what the sing and how they sing. i don't think it should matter if a person is big or if a person is small all that matters is how you perform. so yeah don't worry about what people say like "you can't sing your too big." or " get off the stage biggy" because if you are doing good then you can go on for ever.
wow! that was long lol but that is what i think.