Assuming that a sugar-coated cereal contains 23.0% sugar and no other energy source, what mass of cereal will provide enough energy to walk the 2.0 km? A 70 kg person uses 230.0 kJ of energy to walk a kilometer. This energy comes from "burning" glucose, but only about 30.0% of the heat of combustion of glucose can be used for propulsion. The rest is used for other body functions or is wasted as heat.