Validity and reliability of a new whole room indirect calorimeter to assess metabolic response to small calorie loads

To provide an overview of our whole room indirect calorimeter (WRIC), demonstrate validity and reliability of our WRIC, and explore a novel application of Bayesian hierarchical modeling to assess responses to small carbohydrate loads.Seven gas infusion studies were performed using a gas blender and profiles designed to mimic resting and postprandial metabolic events to assess WRIC validity. In a crossover design, 16 participants underwent fasting and postprandial measurements, during which they consumed a 75-kcal drink containing sucrose, dextrose, or fructose. Linear mixed effects models were used to compare resting and postprandial metabolic rate (MR) and carbohydrate oxidation. Bayesian Hierarchical Modeling was also used to model postprandial carbohydrate oxidation trajectories for each participant and condition.Mean total error in infusions were 1.270.67% and 0.420.70% for VO₂ and VCO₂ respectively, indicating a high level of validity. Mean resting MR was similar across conditions (=1.050.03 kcal/min, <i>p</i>=0.82, ICC: 0.91). While MR increased similarly among all conditions (~13%, <i>p</i>=0.29), postprandial carbohydrate oxidation parameters were significantly lower for dextrose compared with sucrose or fructose.Here, we provide evidence of validation of our WRIC and a novel application of statistical methods useful for research using WRIC.