Obesity is the object of incredible amounts of resources and attention purportedly aimed at reducing corpulence and increasing health. Despite this, consensus with respect to the definition, causes or solutions is lacking, making obesity a prominent knowledge controversy. In this article, I argue that the Barker hypothesis, a theory of foetal development, can support the redistribution of expertise necessary to address this knowledge controversy. A vast scientific literature confirms its argument that many diseases can be traced to the conditions for development in utero determined by the commingling of temporally and spatially complex processes. The Barker hypothesis does not support solely reductionist, biophysiological paradigms of health and disease, but rather evinces complex understandings that span biology, social positionality, place and generation. I argue that this makes the hypothesis significant for transdisciplinary studies of health and disease, and prompts consideration beyond the conventional bounds of epidemiology to new sites of understanding and action that may support movements concerned with body politics and justice for fat people. I point to literature on the potential for injustice engendered by the Barker hypothesis, and suggest that these critiques reveal the very necessity for transdisciplinary collaboration on obesity in the first place.