Type 2 diabetes mellitus (T2DM) is a common metabolic disorder characterized by chronic hyperglycaemia. It is associated with reduced life expectancy owing to a greater risk of heart disease, stroke, peripheral neuropathy, renal disease, blindness and amputation. The best-known predictors of increased diabetes risk are elevated fasting plasma glucose, elevated 1- and 2-hour plasma glucose after an oral glucose tolerance test, obesity and evidence of impaired insulin action. However, the mechanisms by which people with impaired fasting glucose and/or abnormal glucose tolerance ‘progress’ to overt T2DM are not completely understood.