Do you always lose body fat when you burn more calories than put in?

What you're burning typically depends on the type of workout you are doing. It's believed you burn more fat during lower intensity workouts and carbohydrates during high intensity workouts. WIth that being said, you also burn less calories during lower intensity workouts. The main thing is you are burning a lower percentage of fat and more glycogen (carbs) during high intenisty and a higher percentage of fat and lower perecentage of glycogen and low intensity. However, I doubt you would have much energy or feel like completing these workouts if you were only eating doritos and chips, Also, you typically burn more fat if you workout first thing in the morning on an empty stomach. If you were eating like this, you would be getting insufficient nutrition and become sick at some point. You would also need protein to help build and repair muscle while you were working out. You would also need whole grains, veggies, fruits, etc to get the full benefits of your workout. A workout without proper nutrition is pretty much pointless.