On study days, a catheter is placed in two antecubital veins for regular blood sampling and for glucose infusion (if needed). The participant will rest in a bed, when not performing the 1-hour bicycle ergometer test.
Thirty minutes before the leg-cycle ergometer test, the participants consume a 300 ml beverage containing either: 1) dextrose (20 g), 2) galactose (20 g) 3) lactose (20 g) or 4) water (sweetened). At t=0, the ergometer test is started and continued for 1 hour (fixed intensity cycling at 60% of VO2-max). If blood glucose drops below 3.9 mmol/l, glucose infusion (5 % glucose) will be administered, and blood glucose is kept just above 5 mmol/l and infused volume is registered.
Blood samples are collected at t= -40, 0, 30, 60, 90, 120 for measurement of plasma lactate, non-esterified fatty acids (NEFA), plasma triglyceride and hormonal concentrations (epinephrine, norepinephrine, cortisol, and glucagon). Plasma blood glucose measurements are performed at t = -40 and every 10-15 minutes until the end of the study day.
Respiratory exchange ratio is measured by indirect calorimetry (collection of respiratory gasses VO2 and VCO2) pre-exercise, at the end of the exercise bout, and 30 minutes post-exercise. Protein oxidation rate is estimated from urinary urea excretion, and net lipid and glucose oxidation rates are calculated from indirect calorimetry measurements with correction for protein oxidation. Therefor a urine sample will also be collected at the end of the study day.
The bicycle ergometer test is discontinued after 1 hour of bicycling and the participant is observed until 2 hour post exercise where the study day is ended.
