Reducing sugar/carbohydrate - initial effects?

Apologies in advance if this one has been done to death already -
sadly I don't have the time at the moment to look through past
postings so I'm being rather lazy...


Just starting out on a regime of reducing sugar intake in particular
and carbohydrates in general. However a couple of times I've lapsed.
Typically what happens is that I feel very well for 12-24 hours but
then my energy levels seem to fall away and I crave sugar, chocolate,
etc. - to the point where I dash to the shop to buy something to take
the craving away.

This has come as something of a shock because I don't particularly
have a sweet tooth and I didn't think my diet was particularly rich in
sugar. It IS (or has been) quite rich in refined carbohydrates
though.

Any thoughts anyone? Is this little more than withdrawal symptoms?
If it is, how long can I expect it to last before things settle down?

Thanks,
KF