## 1 Introduction: Why Cities Need Food Policies  
The recent report of the Lancet Commission \"Food in the Anthropocene\" [1] confirms some dramatic evidence concerning today's food systems: (1) The current composition of diets does not allow adequately feed the entire world population preserving, at the same time, ecosystems and natural resources. (2) Food consumption patterns of richer economies contribute substantially to global warming, producing huge amounts of greenhouse gases, while those that are emerging in developing countries are based on increasing consumption of red meat [2] and cereals, exacerbating pressures on water resources, soil, and biodiversity [2; 3; 4] (In the period 1961-2016, the greenhouse gas emissions due to agricultural production increased from 3.1 Gt CO\({}_{2}\)-eqry-1 to 5.8 Gt 17 CO\({}_{2}\)-eqry-1, mainly due to breeding, the use of synthetic fertilizers, and the cultivation of rice [2]). (3) Food production, processing, and distribution are among the most impacting factors in terms of climate change, loss of biodiversity, use of water resources, impairment of nutrient cycles, and changes in land use. These issues clearly highlight the paradox that afflicts food systems: despite the challenge for the coming decades to feed a growing world population that is increasingly concentrated in cities [5; 6], the current global food model, dominated by diets strongly impacting on ecosystems and human health, is not able to guarantee this function in a sustainable manner. Furthermore, while 820 million people, equal to 10.9% of the world population,do not have access to sufficient quantities of food has achieved (in 2014, the number of undernourished people was 783 million, equal to 10.7% of the world population), the number of non-transmissible diseases linked to obesity and overweight is growing rapidly [5]. All this happens at a time when, as attested by the last Intergovernmental Panel on Climate Change (IPCC) Special Report on climate change and soil, the availability of food per capita is higher than the average requirement [7; 8]. Furthermore, as the 2007/2008 agricultural prices downturn has shown, globalized food systems are fragile, especially in cities, also in light of estimates of urban population growth rates in the coming decades, and put the issue of food security at the center of political agendas. These changes have been so sudden and of such remarkable impact that a new paradigm has been proposed to describe them, the \"New Food Equation\" [9; 10]. The New Food Equation is based on the evidence that the dynamics concerning the co-evolution between food systems and demographic development are rapidly reshaping the way in which food is produced, processed, distributed, and consumed; impacts the metabolism of a city and its economy; affects public and private spaces [11]; and impacts food consumption patterns and foodscapes. Numerous factors require a theoretical revision of the relationships that the city weaves with the surrounding territory for the purposes of food production, processing, and distribution. The de-territorialization of food systems [12] has manifested itself in a very decisive manner in recent decades, with evident and dramatic consequences on the ability to manage and govern material (materials raw, processed products, and food waste) and immaterial (knowledge, traditions, and consumer-producer relations) flows related to food [13]. Recently, simultaneously with a growing interest of research and institutions for urban-rural relations, cities have begun to think about how to integrate, connect, and protect green agricultural areas and the social, economic, and environmental functions they provide to the well being of the population [10; 14]. Among the approaches to respond to the challenges that involve the transformation of urban food systems, the most widespread today is the City-Region Food System, supported by the Food for the Cities program of FAO in collaboration with the RUAF foundation (Resource Centers on Urban Agriculture and Food Security).