It's so nice to hear people realizing the importance of fat. We don't use "fat" as a way to describe something. We've taught our kids that everyone has fat under their skin and it is an essential part of everyone's body. We say that some people might have more fat under their skin than is healthy (like mommy:)), and some people have too little and some are just right. As for "junk" food, we usually say that food might be good for your body or good for your taste buds. We try to eat more healthy food for our bodies, but in moderation we like to have happy tongues too.
