Why would you top up a tiny tank of fuel when you have a large tank of fuel going unused? Would you buy a car with a 5 litre tank or the car with a 50 litre tank?
Fat v Carbs. I would argue that the following is not fully correct :
"The metabolism of both fat and protein can (and do) provide energy to keep you moving, but the mechanism by which they are utilised is less efficient than that of carbohydrate stores."
A fuel store that can only sustain for "~90 mins" until it is depleted vs a fuel store than can fuel you for many hours without depleting is more efficient, not less.
The intake of carbohydrates limits your bodies ability to metabolise fats, for very high intensity activities then the carbohydrates are requried. However, they are best absorbed post exercise when the muscles (as glycogen is stored locally) are far more receptive when you do take them, so unless you are running relatively hard first thing in the morning and eating after then taking on board carbs is probably not the best way to periodise your day.
Personally, I would suggest a higher protein and fat meal is better for breakfast.
Edited: 13/03/2013 at 11:00