Food security is an increasingly important issue in an era where a growing population of this planet lives in urban areas. In this sense, little is known about the issue in medium- and small-size cities. That is why this article focuses on understanding the implications of food security in relation to the origin, preference and availability of food consumed in the municipality of Autlan de Navarro, in the South of the state of Jalisco in Western Mexico. For the compilation of information on the agricultural production of the municipality, official databases were analyzed. In addition, 25 interviews were carried out with key actors in the area of food production and marketing, as well as 200 surveys to consumers and food merchants in the municipal capital. Main results indicate that the agri-food system in Autlan de Navarro has undergone major transformations that have had an impact on the dynamics of food production, distribution and consumption (for example, food diversity decreased with eight crops from 2002 to 2015). In the Municipality, the main economic activity maintains to be agriculture, but the crops with the highest production correspond to products that are not related to the supply for local consumption in terms of food. On the other hand, corn (considered one of the main sources of food in Mexico), has increased its production, but is mostly destined to foreign markets. Crops of minor importance are being sold in the supply centre of the state capital of Guadalajara, or exported to other states, while most of the local vendors purchase their products to supply said supply centre. On the other hand, several of the products produced locally are almost exclusively for export. Even when consumers show a marked preference for acquiring fresh food products in local establishments, such as markets and groceries, the products that the tenants offer are mostly purchased outside the Municipality. This denotes a clear deficiency in the commercial networks between local producers and merchants of the municipality, which generates a greater external dependence on food (i.e., loss of food security), due to the necessity to purchase an increasing number of foods outside the municipality.