Personally, when I eat it brings down my high in certain ways. Usually if I eat after I smoke I get really lazy, and turn into a couch potato. I like to be active when I'm high, so I usually wait until I know I'm done smoking to eat. This has ran me into trouble a few times though, because I've smoked all day before and never eaten anything the entire time and I started feeling really woozy and sick, like I had low blood sugar. So I ate.