The idea is, a prolonged absence of food brings a reduction in circulating blood sugar, causing glycogen (stored Carbohydrate) levels to fall. Which leaves your body no choice but to rely more on fat, rather than glucose, to fuel workouts.

Also the low insulin levels associated with fasting are conducive to fat breakdown, increasing the availability of fatty acids to be used as energy during the exercise session…

MYTH!

More EPOC(Excess Post Exercise Oxygen Consumption) equals more fat burned. This favors eating prior to performing cardio. Ever try to perform HIIT (High Intensity Interval Training) on an empty stomach? In order to perform at a high level, your body needs a ready source of glycogen; deplete those stores and say goodbye to elevated training intensity.

You Have to eat all nutrients available to you in order to gain muscle and burn fat. There is no easy way out, don’t overthink it. A calorie deficit burn fat on a consistent basis. Hope this helped!