This subject will probably keep being debated on for many generations to come, "does early morning fasted cardio really burn more fat?"
It all started many years ago when certain scientists and fitness enthusiasts started claiming that this way, was the fastest way to experience body fat reduction.
In fact, these people were literally telling people to develop the habit of just waking up, drinking a chug of water and heading outside to run for 45min to 1hr.
But, many studies started revealing that this form of cardio, was only effective at one thing...
Putting your body in a catabolic state so your muscles starve and disappear.
Can you see the contradictions here?
Now, I usually don't like going to sciency on people but sometimes a little science can go a long way in you deciding whats really best for you and your situation.
Here are the positives of early morning fasted cardio:
There are studies that show that this type of cardio increases the amount of free fatty acids that are used as fuel. But whats interesting is that this is not due to doing your cardio in a fasted state when you wake up.
This happens during your sleep and when you enter your deep sleep phases. And seeing that these fatty acids are used as your primary energy when you sleep, about 200 to 300 calories, there might be a chance that when you wake up they might be more readily available to be mobilized for fuel as you do your morning cardio on an empty stomach.
But on the negative side of things, this brings up another point...
If this type of morning cardio increases how fat is used, its probably also going to waste away more muscle.
This is because of the increase of a compound called cortisol, and it appears in large amounts when you are in a fasted state. And since you wake up in a fasted type state, there is a great chance that early morning fasted card can lead to more muscle mass being wasted away than any other time of the day.
So there really is no good or bad answer, it really depends on your goals, and what long term you want to ultimately accomplish.
If your goal is to maximize muscle and you already have a hard time putting on mass, chances are you probably want to avoid this type of cardio.
But on the other hand, if your main goal is fat loss and you aren't concerned with how much muscle you have or want to gain then fasted cardio might be a good option for you.
I recommend that you try it and see what your results are, and after that you can make your decision on whether or not to move forward with it.