unhealthy eating v.s. smoking?!

okay so my girlfriend wants me to quit smoking witch is perfectly understandable. it smells bad it it will kill me eventualy. i know and i get that. the thing is, she has extremely unhealthy eating habits. she eats 4 fast food meals in just one day at times, but she laughs it off and just says its because shes always hungry. if im going to quit smoking, i want her to quit her horrible eating habits. my question is, how can i prove to her that eating the way she does, will kill her just as fast as cigaret smoking will kill me? if anyone knows of good internet sources or medical advice about this subject, let me know. thank you