I've read countless articles each stating different things. Some say that you can go into a "fat burning" zone with low intensity exercise, others say that low intensity causes more muscle loss than something high intensive like HIIT.

Can someone explain to me how cardio can cause muscle loss? Why would HIIT minimize muscle loss and low intensity increase it?

What kind of factors are involved other than just the intensity of the exercise?

Can someone explain to me, or post a link that explains on what variables and factors your body decides whether to use fat for fuel, energy that just came from food, etc.

Because I was planning on resuming my 20-25 minute of Jump skipping to keep my fat gains down on this bulk. I do this at a medium-high intensity in 400-500 revolution sessions ( or maybe more now ). If doing this kind of cardio would cause muscle loss, i'd want to know.