rpenmanparker 

I can share an experience with you. I always have a small breakfast very early in the morning whether I ride or not. Recently I started noticing that a protein breakfast like Egg Beaters and Canadian bacon got me through my ride in good shape. High fiber cold cereal with banana, and milk does not get me through even though (because?) the cereal is quite sweet. I am starting to think the sugar in the cereal is causing an insulin rush that is depleting my glycogen stores which leaves me bonking later in the ride. This is a very highly regarded "natural" brand of cereal, Kashi, so I am really surprised at the effect. I don't know if this makes sense or not; it is just what I am observing. I would say be careful if you eat breakfast before riding to avoid simple sugars. Simple sugars are better ingested during the ride.