This paper uses urban metabolism as a way to understand the sustainability of cities. It suggests that the city organism can reduce its metabolic footprint (resource inputs and waste outputs) whilst improving its livability. Like organisms, different cities have different metabolisms. This paper demonstrates that different parts of a city (walking, transit and automobile urban fabrics) also have different urban metabolisms. A detailed case study from the city of Perth, Australia, is used to demonstrate metabolic variations in different parts of the city. Understanding urban metabolism and the processes that drive it is the key to transitioning from ecologically extractive to sustainable cities. Through targeted improvements it is even possible for some elements of the city to become regenerative so that they restore parts of the degraded urban environment thus reversing damage to the biosphere.