[MENTION=423901]Stratocaster[/MENTION], nothing bad happens to you if you eat too close to a ride. The idea is that you just want the meal digested before you start riding. This is so that your stomach is empty and your insulin responses have returned to normal. In scenarios in which I can't eat 2+ hrs before riding, I either don't eat at all or eat a little less and make sure it's a carby as possible (carbs empty from the stomach fastest and are quickest to digest)- for example you could go for a glass of juice. Or I just don't worry about it and try to start out easy if I can.
When your body is trying to blow off C02, you have a quicker and more shallow respiratory pattern. [MENTION=78894]Carbonfiberboy[/MENTION] describes it as panting, which is a good description I think, keeping in mind that its not as rapid and shallow as a dog's pant. The frequency is the big clue, it is rapid- not a big deep sigh.