howdy,
lets say you consume 2000 calories a day for a week.
and at the end of the week you have lost a pound of bodyfat.
1 lb of fat being approx 3500 calories.

does this mean at the end of the week you have burnt 17500 calories ( what you ate and from the fat lost).

as you are infact using these stored calories why is it so hard to gain muscle and loose weight at the same time.