Metabolic Chamber Measures

To measure 24-h energy expenditure (24-h EE), participants of study 1 spent approximately 23.5 h inside a whole-room indirect calorimeter as previously described (18). To account for reduced physical activity inside the chamber, predefined energy intake in the metabolic chamber was approximately 80% of the weight maintaining diet and based on previously developed equation (26). All unconsumed food was returned to the metabolic kitchen for weighing for an accurate calculation of intake. To calculate 24-h EE and 24-h RQ, carbon dioxide production and oxygen consumption were extrapolated to 24 h. Energy intake minus 24-h EE was defined as 24-h energy balance (ENBAL). The volunteers with ENBAL greater than 20% were excluded from the analysis involving energy expenditure and respiratory quotient. From the 24-h RQ, 24-h carbohydrate oxidation (24-h CARBOX) and lipid oxidation (24-h LIPOX) rates were calculated accounting for 24-h protein oxidation (24-h PROTOX) obtained by the measurement of 24-h urinary nitrogen excretion as previously described (27). Radar sensors were used to detect spontaneous physical activity (SPA) expressed as the percentage of time over the 24-h period in which activity was detected. The average energy expenditure between 2330 and 0500 during which SPA was < 1.5% was defined as sleeping metabolic rate (SMR).