As supported by experimental and clinical data, oral carbohydrate tolerance is influenced by the coingestion of nutrients through multiple mechanisms. The ingestion itself, the contact with the gastric mucosa, the arrival into the intestine and the subsequent digestion are known to produce neural reflexes, hormonal responses and plasma substrates gradients which, by modulating gastric emptying, insulin secretion and insulin clearance participate in the regulation of postprandial glycaemia. The size of this effect is influenced by a number of factors: the specific nutrient chemical characteristics (fat vs protein and composition) and their physical properties (solid vs liquid), the timing (pre-load vs coingestion) and finally the individual glucose tolerance status. To our knowledge, the effect on glucose excursions of a combination of protein and fat given before carbohydrate is still unknown and also unknown is the contribution of different mechanisms involved in the control of glucose homeostasis in subjects with different degrees of glucose tolerance.