The discovery earlier this year that a variant of the TCF7L2 (transcription factor 7-like 2) gene is associated with type 2 diabetes was reported in a front page story in the New York Times.¹² The principal investigator, Kari Stefansson, told the newspaper that the discovery could lead to a diagnostic test to identify people who carry the variant gene. People who knew of their extra risk, he said, would be motivated to avoid the lifestyle habits that lead to diabetes. A Scottish scientist headed the research team, which led the Glasgow Herald to report, “Discovery of holy grail will help scientists treat diabetes.”3

Undeniably this discovery is noteworthy. Type 2 diabetes is a leading cause of morbidity and mortality in the developed world and is increasing in prevalence worldwide. The association is robust—the finding has been replicated in three large independent study populations and offers potential new insight into the pathobiology of diabetes. Yet the claim that this knowledge will …