This diagram provides another perspective on energy stores and how long these stores would last if used to fuel continuous activity. Clearly illustrated is the large disparity in running distance when the fuel is based exclusively on carbohydrate stores versus exclusively on fat stores.
Body weight affects the energy cost of movement.
A heavier person expends more calories per mile while a lighter person expends less. Each individual substrate is used as the exclusive energy source to fuel running. The total body store of muscle glycogen is available as fuel for a given activity. Actually, only the muscle glycogen stored in muscles that are contracting can be accessed to fuel a specific activity.