Changes

One limiting factor in running marathon distance races is our ability to store [[Glycogen]]. Because glycogen [[Glycogen]] is only stored in the muscles and liver, excess body fat reduces the percentage of muscle and therefore percentage of glycogen [[Glycogen]] that can be stored.

You might think that more body fat would help provide fuel on very long runs. However, one pound of fat provides about 3,500 calories, enough to fuel a runner for 35 miles, assuming no other fuel is used (eaten, glycogen[[Glycogen]], etc).