In the years since the World Health Organization (2000) released its warning of a pandemic of “globesity” spreading from the so-called developed to the so-called developing world, global health agencies have become increasingly invested in producing knowledge about the relation between eating and health. Attention has been directed at understanding the aetiology of obesity in order to establish effective public health interventions, which are often couched in terms of managing the ever-growing costs of non-communicable diseases to national health care systems. There is simultaneous concern about how countries can address the “double burden” of hunger and obesity, each linked in complex ways to “hidden” and intergenerational micronutrient deficiencies, chemical exposures, and immunological burdens. The crafting of policy around dietary health and illness unfolds in a context that the global media has infused with a sense of urgency. Ambivalent evidentiary practices emerge out of the rapidly changing terrain of metabolic research, shifting the nature of evidence and the pathways between research and intervention.