Between the late 19th century and the early 20th century, a new cultural framework which crossed boundaries between science, medicine, technology and society started to emerge in Colombia converging in the problem of nutrition. In this context, the old analogy of the human body as a machine started to take a new meaning shaped by, among others, thermodynamics, experimental physiology and comparative statistics. In 1884 the streets of Bogotá displayed the first rails built by a local company, and four years later the first steam engine, built entirely in Colombia. Contemporaneously, the National University of Colombia trained students in civil engineering and medicine who in their early preparation, before specializing in their respective trades, encountered courses such as ‘medical physics’, where knowledge about the functioning of machines and human bodies converged. Furthermore, the thermal machine analogy also found its way in the physiological study of nutrition charged with social and political implications. This paper explores how the human machine metaphor can be understood as a cultural artefact that incarnated an assemblage of heterogeneous knowledges, practices and instruments and that helped to define new social problems and strategies to solve them. First, the paper explores different places where knowledge about the human body was produced. Besides pedagogical spaces as the aforementioned course of medical physics, I explore sociological reflections and field research performed by physicians, engineers and lawyers about the living conditions of the working class where the human-machine metaphor operated and acquired new meanings. Second, this paper focuses on the laboratory work of physiologist Calixto Torres, who in the early 20th century measured the caloric content of local food, and the capacity of nutrient absorption of high altitude inhabitants from Bogotá and Tunja. Based on statistical comparisons, he concluded that these local “races” were “physiologically degenerated”; they were thermal machines with a low capacity to transform available energy. This kind of work, that produced knowledge about both nature and the social, and that blurred epistemological and disciplinary demarcations, helped to build nutrition as a social problem destined to be solved by public health programs aimed at teaching people how to become efficient machines. Finally, I analyse some of the institutions that were created for this social engineering goal.