The aim of this research was to examine differences between measured resting metabolic rate (RMR) from a portable indirect calorimeter (IC) (Breezing®) and calculated RMR from the recommended Mifflin-St. Jeor (MSJE) predictive equation.
Seventy-nine subjects were recruited for the study approved by Arizona State University’s IRB. Three RMR measures with the IC device were averaged and compared to RMR values calculated using the MSJE. Subjects were divided base on body fat%. Group A (n=35; body fat%: 16.9±5.7; BMI: 21.9±2.4 kg/m2; age: 27.8±4.5 years) included 19 males and 16 females. The overweight group B (n=44; body fat%: 41.7±8.7; BMI: 35.4±6.2 kg/m2; age: 52.4±13 years) included 13 males and 31 females.
For Group A: The mean RMR by IC was an average of +212 kcal/day higher than MSJE for Females (IC=1462±197; MSJE=1250±182; p=0.01) and slightly lower by an average of -90 kcal/day for males (IC=1660±327; MSJE=1750±157; p=0.32); r2=0.947. Considering a cut-off difference (calculated RMR - measured RMR) value of ±200 kcal/day, the RMR by IC was lower than MSJE for 28% of subjects (n=10) and higher for 43% (n=15). Differences (calc. RMR – meas. RMR) ranged from -890 to +670 kcal/day. For Group B: The mean RMR by IC was slightly lower by an average of -59 and -356 kcal/day for females and males, respectively (females IC=1468±264; MSJE=1527±229; p=0.38 and males IC=1647±383; MSJE=2003±162; p=0.05); r2=0.943. Considering a cut-off difference (calc. RMR – meas. RMR) value of ±200kcal/day, RMR by IC was lower than MSJE for 39% of subjects (n=17) and higher for 20.5% (n=9). RMR by IC versus MSJE felt within ±200 kcal/day for 41% (n=18) of subjects. Differences (calc. RMR – meas. RMR) ranged from -660 to +950 kcal/day.
Analyses indicated no significant differences between the calculated and measured RMR for the groups (p<0.01). These results support the use of the mobile IC to provide more personalized and accurate measurements of RMR.