There is tons of controversy over to do morning fast cardio, or to eat before. Truth is, depends on the goal, the person and how you go about it.
Research from the “British Journal of Nutrition” show you burn up to 20% more fat when you are fasted.
*Being completely fasted before cardio can be effective because your body conserves carbohydrates overnight and begins to mobilize fat for fuel. The body also breaks down amino acids into glucose overnight. So the body will use up more fat AND potentially amino acids for fuel. This is not ideal if you want to build muscle. Therefore, if you are going to do fasted cardio, make sure to at least drink some amino acids beforehand, and consume a fast digesting protein, such as whey, and pair it with a slow digesting casein after cardio.
However, performing HIIT cardio (High Intensity Interval Training) burns more calories and fat post workout, than low intensity. This means, that you will be burning calories more rapidly for the rest of the day, even at rest. It actually burns twice the total fat loss.
For a straight answer, don’t worry about being fasted before your workout.
-For some, like females with trouble areas in the legs, fasted cardio can work well.