- chronic high protein intake: on the third occasion, they will have received an hypercaloric diet ( 130% energy requirement, providing 42% carbohydrate, 23% fat, 35% protein; this corresponds to the isocaloric diet given on the first two occasions, additioned with 1g/day protein) during 4 days. On the morning of the 5th day, they will be studied for 2 hours in basal, post absorptive conditions and over 6 hours following ingestion of a meal providing ca 12.5 kcal /kg body weight and containing 45% carbohydrate, 30% fat (of which 13% medium chain triglycerides (MCT) labeled with 13C3 trioctanoate) and 25% protein. The three tests will be done in a randomized order, with a washout period of at least 4 weeks between each test.