This happens to me as well. In a sense I'm glad it "goes right through me", in my head (which I know isn't the case, oh well) I think that since it comes out so quickly after eating, all the bad stuff musnt really be staying in my system. haha , oh ignorance is bliss sometimes.
Fast food such as McDonalds does this the most for me.
"I can do all things through Him who gives me strength" Phil 4:13