It's called withdrawl symptoms. Basicaly your an addict who has had his drug of choice taken away (in this case sugar). If you are also withdrawing from caffine, then definetly normal.

Make sure to take suppliments to help with this though. Also make sure to eat enough so that plain old hunger isn't making you irritable. Get enough fat in and eat when hungry to keep the nasties at bay.

Make sure to read the book as much f this is covered. Also read the web site many times, especially the induciton section.