Is it at all important wether it is fat or carbohydrate that is burned during exercise?
Not if your focus is lowering bodyfat levels.
The determining fact is wether there is a caloric deficit, wether you burn fat or carbohydrate during exercise is irrelevant. Hint: look at sprinters.
There are many potential problems with not ingesting carbohydrate during your workouts: you might end up using amino acids (muscle) for energy. Not an optimal situation!
With regards to the low blood glucose levels and high insulin levels it is not likely to occur during exercise:
glucagon and cortisol levels are elevated during exercise. These hormones “draw” fat and glucose in to the bloodstream, this prevents low glycose levels during exercise
Insulin response is blunted during exercise. What mechanism governs this I don’t know…
In short: High insulinlevels and low blood glucose levels are not likely to occur during exercise.
With regards to the amino acids in whey being used as energy during exercise: what scenario do you prefer?
Amino acids from muscle being used or amino acids from your whey shake?
I can’t really understand the reason for this interlectual exercise?
There is no reason not to ingest carbohydrates during exercise. This is the time during your day you are least likely to store fat!
So as you see the point is not burning the most fat, it is avoiding fat accumulation.
Hope it made sense…