The implications of pharmacogenomic innovations for human difference and technological progress, along with the hopes and risks they bring forth, have been addressed as a major area of tension among scientific, personal, and political interests. This article explores the consequences of such clashing concerns in Japan by drawing on current ideas of postplurality within STS and anthropology. How does the body of the diabetic patient—from (thrifty) genes to fat bellies—become an experimental site of biotechnological and public health innovations in contemporary Japan? What is at stake when these bodies move across different locations and scales in the comparative practices of pharmacogenomics? These are the questions I pursue through an ethnographic presentation of adiponectin, a fat-cell-derived hormone that has attracted considerable attention during the past decade in the study of diabetes. By exploring three planes of the adiponectin research (genetics, epidemiology, and drug discovery), the analysis of this case study suggests that genes and populations, publics and scientists, cardiovascular disease and diabetes are not static objects of medicine but rather interfere with each other in their differences through a series of comparative practices, such as linkage analysis, haplotyping, or clinical trials. Such comparisons across populations, markets, disciplines, and disease entities require and generate a permanent traffic between genetics and epidemiology, highlighting the specific dynamics between these scientific realms. In this new form of medicine, I argue, the prevention of disease aligns illness entities with drug responses in a biopolitical work of differentiation, with significant consequences for traditional methods of social research.