Indirect calorimetry (IC) measurements to estimate resting energy expenditure (REE) necessitate a stable measurement period or steady state (SS). There is limited evidence when assessing the time to reach SS in young, healthy adults. The aims of this prospective study are to determine the approximate time to necessary reach SS using open-circuit IC and to establish the appropriate duration of SS needed to estimate REE. One hundred young, healthy participants (54 males and 46 females; age = 20.6 ± 2.1 years; body weight = 73.6 ± 16.3 kg; height 172.5 ± 9.3 cm; BMI = 24.5 ± 3.8 kg/m2) completed IC measurement for approximately 30 min while the volume of oxygen (VO2) and volume of carbon dioxide (VCO2) were collected. SS was defined by variations in the VO2 and VCO2 of ≤10% coefficient of variation (%CV) over a period of five consecutive minutes. The 30-min IC measurement was divided into six 5-min segments, such as S1, S2, S3, S4, S5, and S6. The results show that SS was achieved during S2 (%CV = 6.81 ± 3.2%), and the %CV continued to met the SS criteria for the duration of the IC measurement (S3 = 8.07 ± 4.4%, S4 = 7.93 ± 3.7%, S5 = 7.75 ± 4.1%, and S6 = 8.60 ± 4.6%). The current study found that in a population of young, healthy adults the duration of the IC measurement period could be a minimum of 10 min. The first 5-min segment was discarded, while SS occurred by the second 5-min segment.

Level IV-case series.

No abstract

BackgroundResting energy expenditure (REE) measures the amount of calories needed for the body to maintain basic function over a 24‐hour period. Traditionally, REE protocols through indirect calorimetry take 45 minutes to complete. Generally, the first 10 to 20 minutes of data collected are excluded to allow the participants to reach steady state.ObjectiveThe purpose of this study was to determine a more precise time to reach a resting steady state.MethodsFifty healthy, adult male and female participants volunteered for this study. Each participant completed indirect calorimetry after a 12‐hour overnight fast. Participants were instructed to lay supine and awake under a plastic canopy for approximately 30‐minute, while oxygen consumption (VO2) and carbon dioxide production (VCO2) measures were collected. These values were used to determine steady state REE (kcals•day‐1) and respiratory quotient (RQ). Statistical analysis for the response of variables to time was modeled with a logistics decay function. Data are reported as mean ± SD with an alpha level of 0.05.ResultsPredicted time to steady state REE in kcals•day‐1 and in kcals•day‐1•kg‐1 was reached at 15.09 ± 0.1 minutes and 15.10 ± 0.1 minutes, respectively. There was no significant change in REE thereafter. In addition, respiratory quotient values from the first 15‐minutes (0.91) to the last 15‐minutes (0.86) were significantly different (p < 0.001).ConclusionIndirect calorimetry to measure steady state resting energy expenditure should exclude the first 15‐minutes in a young, healthy population.