Originally Posted by RUOkie

that is pretty accurate, although the reserve part can be very variable. The more you train at endurance events, the more you store, but there is an upper limit to us all and that is determined by genetics That is why a lot of people currently advocate occasionally training on an empty stomach to stress the system Obviously that is not something you want to do every day.
@Heathpack. The advantage to gels and blocks are that they are very rapidly absorbed, with little to no digestion needed (just your salivary amylase) So you can take in 100 kcal and within a min or two you can use it.