Comparison Of The Body Gem And The Harris Benedict Equation For Determining Resting Energy Expenditure

Abstract

The ability to accurately measure resting energy expenditure (REE) is essential in both the study of exercise science and human nutrition. The Harris Benedict equation (HBEq) is commonly used by nutritionists to estimate REE when developing weight loss programs. Relatively inexpensive portable indirect calorimeters for estimating REE have been developed which measure oxygen consumption but when estimating caloric expenditure rely on the Weir equation which assumes a respiratory exchange ratio of 0.85. PURPOSE: to compare measurements of REE using the Body Gem (MicroLife, Dunedin, FL) and the Harris Benedict equation with measurements obtained via indirect calorimetry. METHODS: Twenty-five adults (12 females: age 26±5 years, wt 54.7±8.0 kg, ht 157.3±7.4 cm, BMI 22.1±3.3, body fat 23.5±6.4 %; 13 males: age 26±4 years, wt 79.7±15.7 kg, ht 172.4±6.2 cm, BMI 26.7±4.4, body fat 15.5±6.0 %) were tested following a 12 hour fast. Anthropometric data were collected to estimate REE using the HBEq. Following a 30-minute rest in a semi-recumbent position, REE data were obtained via indirect calorimetry during the last 5 minutes of a 30 minute collection period. REE was then estimated for all subjects using the Body Gem portable indirect calorimeter by breathing through the device for 5-12 minutes until steady state was detected. The Body Gem was held in place by a rolled-up towel so that subjects were not required to hold the device during data collection. RESULTS: Mean REE (kcal/day) for all subjects were: HBEq = 1609.7±312.7, Body Gem = 1280.5±255.9, Indirect calorimetry = 1321.7±317.8. Mean REE (kcal/day) for males and females were: HBEq = 1853.4±233.4 and 1345.7±88.1, Body Gem = 1468.3±195.7 and 1077.1±119.2, Indirect calorimetry = 1543.9±267.3 and 1081.0±144.4, respectively. REE estimated from HBEq was significantly higher compared to indirect calorimetry (p<0.05). No significant differences in REE were found between the Body Gem and indirect calorimetry. CONCLUSIONS: The HBEq significantly overestimated REE in healthy young adults by 288 kcal/day(21.8%). The Body Gem provided valid estimates of REE and may be used as a substitute for indirect calorimetry to estimate REE in the development of weight loss programs. The HBEq should only be used when other, more accurate methods for estimating REE are not available.