Originally Posted by Phatman
since this is a rest week, it could be that your glycogen is just replenishing itself. remember, your body can store ~400 grams of glycogen, and thats a pound right there. Also, each gram of glycogen holds about 3 grams of water, so thats another three pounds. If you were seriously overtraining, your glycogen was probably depleted, and your just starting to restore it on your rest week.
Ahh, so that's what's happening! I've noticed that after a period of hard riding I'll lose about 4-5 pounds, and then put it on again over the next few days.