Cities are responsible for the majority of global resource use and greenhouse gas emissions. Urban metabolism, which mimics metabolism of organisms as both require material and energy to function and further generate waste and emissions, is a useful framework to analyze levels of sustainability of a city through quantification of material and energy flows it uses and discards. The present study quantifies and compares the metabolic patterns of the four main Danish cities, Copenhagen, Aarhus, Odense, and Aalborg, from 2010 and 2015. We found their inflows of energy, water, and food and outflows of greenhouse gas emissions, wastewater, municipal solid waste, and construction and demolition waste have downsized over the six years. Our results affirm the impact of relevant policy and regulations in urban sustainability, with Danish cities showing more sustainable metabolic patterns than other world megacities previously reported in the literature. They also indicate that urban metabolic patterns can be highly dependent on the role and services that a city offers to its surrounding region (as a multicellular organism). Further strengthening of policies and regulations on “cities for sustainability” (i.e., focus on the sustainability of the entire multicellular organism) instead of a sole focus on “sustainable city” (i.e., each cell aiming at being sustainable independently from the others) would be important.