I don't know the answer to your first question, but I have noticed that when I have lots of bread or sweets, I get really dehydrated and need to drink about two litres/quarts of water before I feel better. It feels as if the carbs 'soak up' a lot of water.
The weight stays up for a few days and then usually drops drastically.
This is not a scientific explanation, but just my experience.
Advance, and never halt, for advancing is perfection.
By Khalil Gibran