Join Date: Jan 2002
Location: Orlando, FL
Bikes: litespeed, cannondale
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Here is my take on it.
Your body burns either carbohydrate or fat. Burning carbohydrate can sustain higher levels of exertion than fat burning. When you burn fat, you liberate only half of the energy that you do burning carbos per oxygen molecule.
So why don't you store all of your energy as carbohydrate. Because fat weighs half as much as carbohydrate per energy unit. But it is so very hard to get rid of. Bodies hang onto fat so they can survive that famine that is around the corner.
Now generally, in a trained aerobic athelete, they will burn fat and carbohydrate at lower exertion levels and almost 100% carbohydrate at high exertion levels. I can go out and ride 50 miles first thing in the morning without eating anything. I am ready to eat something when I come home. I think in these rides I have burned a fair bit of fat so I still have significant carbo reserves. But if I go out in a fast club ride and hammer with them for 50 miles, I come home and I am ravenous. In these high intensity rides, I have probably come close to depleting my carbohydrates and my body wants an immediate refuelling.
I would think that you are starting out. I think that for new people, during exercise the body burns carbohydrates. It takes awhile for the body to concede that it might have to burn some of its precious fat (bodies are perverse). So you go out and after 10 miles, you have put a dent in your carbo reserves and you body wants to bring them back up to normal. FEED ME! FEED ME! I think if you keep up doing your rides, you will notice that the hunger pangs will decrease in intensity as your body uses fat more as a source of energy.
The above is based partially on well understood biology and partially on my interpretation of how people's bodies respond to exercise. In your case, I could very easily be wrong. There is an amazing amount of variation in how individuals respond to exercise.