Effects of a Small Protein and Lipid Preload on Glucose Tolerance in Subjects With Impaired Glucose Homeostasis

The purpose of this study is: * to measure the size of the effect on glucose tolerance of a small mixed protein and lipid meal given as a pre-load in individuals with different glucose tolerance status * to investigate the underlying mechanisms by accurately evaluating beta cell function, insulin sensitivity, insulin clearance and glucose kinetics (oral absorption, endogenous production, rate of utilization) together with gut hormones plasma concentration.