Just a thought - the need for gelling

Just posted on RR's forum.

I was just thinking this on the way home from work yesterday. Why do we need gel for those long runs (yes this just been discuss on the general forum)?

I was reading an article on Runner's World where when you are doing aerobic activities, u are burning mainly fat. U will never get to burn 100% fat. There will be some carbs that ur body will burn as well. Since our body hold more fat than carbs, our carbs will be the first to run out. I assume this is the feeling of hitting the wall.

I am always curious as to why the gel has only 100 calories. On my 3 hr runs, i burn at least 2000 calories (that's about 4 big macs icon_biggrin.gif). How can a gel with only 100 calories be able to fill me up? For a 3 hr run, i take about 4-5 gel (50 min first one, then every 30 min afterwards). That's 500 calories.

From my HRM, during my long run, i burn avg 60% fat. So 40% must be carbs. So 40% of 2000 is 800. My gel intake is 500 calories. That's pretty close to sustaining the carbs i burn. This is getting quite analytical. I am not sure if anyone else have thought about it like this before.

Note: I am sure I don't need to refuel the full 800 calories b/c my body have some carbs in storage. I am also guessing that since my body will not be effciient, it won't absorb the full 100 calories. Like, u can never drink enough water to replenish the water u lost during long duration activities.