Prevention of type 2 diabetes mellitus (T2DM) has been studied in several randomized clinical trials1-6 in adults at high risk of developing diabetes. Most enrolled only persons with impaired glucose tolerance (IGT) during an oral glucose tolerance test (OGTT). Other high-risk characteristics often included obesity and elevated fasting plasma glucose (FPG) level. All these studies had OGTT-diagnosed diabetes as the primary outcome, although exact definitions differed among studies.