Fat loss and muscle loss when losing weight..

[ambuletz]

Just wondered if anyone knows... How does the body work with respects to burning fat or muscle when you are on a deficit? When you start to feel hungry does it eat into your muscle or your fat stores?
I want to make sure that as I'm doing my cardio/weights that any drops in weight are only due to fat loss and not muscle loss.
Yes I understand that you should do HIIT or lifting to ensure you maintain muscle. and eat enough protein. How does this compare to a day where I decide to do some cardio on an empty stomach? Would this be more efficient at burning the fat? Or will this eat into muscle too? Or does it not matter too much and just eat/exercise whenever as long as there is still a deficit.
I haven't lifted since the friday before last and have noticed about 4-5lbs drop. Which makes me wonder if all of that is fat, or all muscle or a combination.