Participants will turn in the supplement tray to verify compliance with ingesting the capsules. A blood sample will be collected. Participants (walkers) will be randomized to either sit for 45 minutes in the lab or to walk briskly for 45 minutes on a 5% graded treadmill at 60% VO2max (with metabolic monitoring during the first 5 minutes, and then at 15, 30, and 45 minutes) using the Cosmed CPET metabolic cart. Runners will run at 70% VO2max on an ungraded treadmill for 2.5 h, with metabolic measurements made every 30 minutes. Water will be given ad libitum for all participants, with no other beverage or food allowed. Just prior to the sitting or walking lab sessions, and the 2.5 h run, participants will consume a 150-ml solution containing 1 g sucrose, 1 g lactulose, 0.5 g L-rhamnose, 1 g erythritol, 1 g sucralose, 0.5 g mannitol.