I've got this and to avoid the confusion about it here's the doctors definition: Its your bodies inability to REACT APPROPRIATELY to sugar. Usually the body over reacts to sugar by making too much insulin.

The critical thing in dealing with it is to try and limit the absorption rate of sugars. My advice is to cut out anything with caffeine in it and stop drinking any carbonated drinks as these 2 will help slow down the uptake of sugars for starters.
The trendy diet at the mo is the Low GI thing and the good news is that this is perfect for you. Get a copy of one of those and you eat that way and all of a sudden you'll be on so much more of an even keel. More energy, no more severe mood swings, not feeling hungry all the time.

Unfortunately alcohol is uber bad in terms of absorption rate and effective sugar content so if you're going to have a few bevvies then eat a good low GI meal before hand and drink slowly.

If you want more specific advise on what foods I've found to be good then pm me.

Good luck