I too felt awful for the first couple of days and felt really sick and wobbly and quite faint (as well as hungry).
I thought if it's like this the whole time i'll never be able to stick to it but as others have said once you get past that initial first few days and get into ketosis you feel much better.
I actually feel much healthier than i did prior Exante as i don't get regular headaches like i used to, almost daily, which i put down to drinking pretty much only diet coke before and nothing else.
Of course i still crave food and i guess that'll not change and certain times of the day when i used to eat are still hard to get past (i've been on Exante for 4 weeks now) but i don't actually feel hungry just have the urge to have that pleasurable eating feeling like i used to.
Most folk seem to get into ketosis after a few days. I think it was maybe 4 or 5 days for me.
Good luck. Stay strong. It does get easier.