The early cross-sectional study of GLP-1 secretion by Toft-Nielsen et al [7], which reported progressively diminishing GLP-1 responses after mixed meal stimulation in those with impaired glucose tolerance (IGT) and type 2 diabetes, has often been interpreted as indicating longitudinal changes, from normal GLP-1 secretion in healthy individuals to somewhat reduced GLP-1 secretion in those with IGT to substantially reduced GLP-1 secretion in people with type 2 diabetes. This evidence concerns the gene GLP1R and Impaired glucose tolerance.