Sweetz-ness!
hey there,
remember i said i would ask my bf for you, well he says as far as i can remember that the chewing wouldnt cause the roundness but would strengthen ur jaw and also lifting heavy weights would strengthen it too and therefore your face would change, he also said you might put weight on ur face thus giving the appearance of being rounder - he also said that if u do chew as much gum as you do ur going to have a laxative problem 
I thing chewing gums helps to increase the strength of your teeth and I have heard that it also helps in digestion.I think all most people use it and also like it.