Carb cycling explained

I saw a few threads asking about this, but didn't see any great responses. I did a search and didn't find a whole lot on this forum. I found this article on the net which explains it pretty well. I'm just beg to experiment with my diet and carb cycling and found this article helpful:
http://www.******** . c o m /readTopic.do?id=811783

http://www .t - n a t i o n . c o m /readTopic.do?id=811783

Here's another good one:
http://www. b o d y b u i l d i n g . c o m /fun/par30.htm

Just wondering if anybody replaces the lost carbs for pro or fat. If so, do you replace all of the lost calories, or just part?