That 7700 per 1kg figure is for Fat. However what you burn through first are Glycogen stores [1] which store about as half as much energy in the same weight as

That 7700 per 1kg figure is for Fat. However what you burn through first are Glycogen stores [1] which store about as half as much energy in the same weight as a more readily available form. https://en.wikipedia.org/wiki/Glycogen https://en.wikipedia.org/wiki/Glycogen