2.4. Indirect Calorimetry
In conjunction with the oral glucose challenge, indirect calorimetry was performed using a ventilated hood (ParvoMedics, Inc., Sandy, UT) to determine the expired volume of oxygen (VO2) and carbon dioxide (VCO2). Briefly, participants arrived in a fasted state and were instructed to rest supine for 30 min with the lights dimmed to ensure a rested state. Then a ventilated hood was placed over the participant’s head and shoulders. Exhaled air was continuously measured for the 30 min preceding glucose ingestion (0 min) to measure resting energy expenditure (REE) and substrate oxidation. We repeated these measurements at the 60 min and 120 min time points. REE, RER, carbohydrate, and fat oxidation were calculated according to previously published equations [