 After recovery, a catheter will be introduced in the second duodenum via the nose and the position of the catheter will be checked fluoroscopically. This catheter allows collection of intestinal fluids by means of a syringe to collect duodenal fluid aspirates and characterization of the bile acid composition of those samples 8. After 30 minutes, the participants will be given a specified amount of water 250 mL fasted state and another 30 minutes later a nutritional drink fed state. Intestinal fluids will be sampled every 15 min for a period of 1 h before the liquid meal intake and until 90 minutes after the liquid meal intake. So, after the total collection period, 7 fractions for the fed state and 4 fractions for the fasted state will be obtained per participant in a time frame of 2 hours and a half. The composition of bile acids of the intestinal samples will be determined by GC-MS-selected ion monitoring analysis. 