This site says: http://www.cptips.com/nutrtn.htm
"In order to avoid the "bonk" (the shift to fat metabolism with an accompanying deterioration in performance), supplemental carbohydrates need to be eaten during the early stages of rides that will be more than longer than 1 to 2 hours in length to supplement (and thus spare) the body's own glycogen stores."
I thought if I was doing aerobic exercise that I started burning fat after 20 min.
They are saying 2 hours after glycogen stores are depleted that I will start metabolizing fat, thus zapping me of riding energy, but If Im metabolizing fat I don't care how much energy I have to ride. Again though I thought I was metabolizing fat after 20 min of aerobic exercise.