@Zoth: I'm thinking about someone healthy who can do this. Maybe advanced meditators, but the only examples I find are of people who can AP after minutes, not quite instantly.

Why do you say that?
...but feel really sleepy after eating (not immediately after though), so personal experience (I've tried IF before) and posts you can find on internet although it's not the same for everyone, so just giving a hint to who wants to try himself. Now I have to go, 00:11 here!