How to burn fat and avoid burning muscle while doing empty stomach cardio
You wont burn muscle if you do cardio or weight training while in fasted state as fasting increases your GH(Growth Hormone) which is most important for burning fat and muscle rebuilding. In a way it will shield your muscular mass.
Two major hormones play big part in building muscle and burning fat:
There is a good co relation between them
Testosterone is Inversely proportional to Insulin i.e when your insulin is high you gain weight and vice - versa.
In the morning when your body by default is in fasted state your GH is high as insulin is low and that is why you can burn more fat then the cardio after you have your breakfast.So, maintaining low level of insulin is the key to lose weight.
I hope this helps you
Thanks and Best of Luck