"We don't need energy in order to go workout. We have thousands of calories stored in our liver, in our muscles, in the glycogen, in our fat stores, even the amino acids in our muscles can be used to fuel movement if needed. The human body runs on a variety of fuels even though our primary intake sources are carbohydrates, fats and proteins. We can run on lactate, ketone and glucose."
"When you take carbohydrate before a workout, you alter the metabolism and shift from a process called autophagy, which is self-eating. When you workout hungry, your cells actually consume the damaged proteins inside your cells and recycle them into fresh new structures. Every workout tears muscle protein, tears actin and myosin. So what's going to happen to those damaged tissues?"
"Well, they're going to be degraded by autophagy, this process of internal consumption of damaged proteins and be recycled as fresh proteins. So you're making new healthy cell tissue at a much higher rate if you train hungry. The minute you have any carbohydrate before you go workout, you're not going to burn fat now. You're also going to completely shut down autophagy, because it only operates when insulin is virtually zero." - Art De Vany, economics professor and nutrition expert