Location: Obesity and Metabolism Research Unit
Title: DO HAND-HELD CALORIMETERS PROVIDE RELIABLE AND ACCURATE ESTIMATES OF RESTING METABOLIC RATE? Author
Submitted to: Journal of the American College of Nutrition
Publication Type: Review Article
Publication Acceptance Date: September 27, 2006
Publication Date: December 1, 2007
Citation: Van Loan, M.D., Herring, E. 2007. Reliability and validity of a hand-held indirect calorimeter. Journal of the American College of Nutrition, Vol.26, No.6, 625-629. Interpretive Summary: Obesity is the number one public health problem in the US today. Consequently, there is a focus on reducing body weight. Body weight can be reduced by both diet and exercise. However, dietary restriction is known to lower resting metabolic rate and thus reduce the number of calories needed to maintain bodily functions and systems. Conversely, exercise increases metabolic rate. Ideally, weight reduction should include both moderate diet and exercise; thus maintain metabolic rate. To date, assessment of metabolic rate has required expense equipment and trained experts to operate the instruments. However, a new hand-held device, called Body gem, for the determination of resting metabolic rate is available to the consumer. The accuracy of the new device, however, has not been established. We asked 20 healthy men and women to test the 3 new Body Gem instruments and to participate in laboratory measurement which would confirm the accuracy of the device. We found that the individual instruments did provide reproducible results, but the results were not the same for the 3 instruments. We also compared the results of the 3 Body Gem devices to standard laboratory methods and found that only 1 of the 3 devices matched the results obtained from the laboratory methods. It is our recommendation that these new devices be used with caution for monitoring resting metabolic rate.
Technical Abstract: Introduction: Numerous studies have used indirect calorimetry. Most methods are cumbersome, expensive, and difficult to perform. The need exists for a simple, inexpensive, accurate instrument to measure resting metabolic rate. Purpose: This study examined the reliability of a hand-held indirect calorimeter, Body Gem' (BG), and validated the device against a metabolic cart. Methods: Phase I examined the reliability of three BG instruments by repeated testing in random order. Each instrument was tested three times on 3 different days. Phase II validated the BG instruments against a metabolic cart. Repeated measures ANOVA was used to determine if significant differences existed within and between the BG instruments and the metabolic cart. Results: Twenty-four subjects (M=12; F=12) completed Phase I of this study. Ten subjects from Phase I completed Phase II (M=5; F=5). In Phase I, within instrument reliability was demonstrated, but between instrument differences were observed (p < 0.05). This difference was seen in both males and females. In Phase II, two of the three BG instruments gave significantly lower results compared to the metabolic cart (p < 0.05); these results were seen in the females and combined group. Conclusion: Intra-instrument reliability was demonstrated, but between instrument reliability for instruments B and C only. Only 1of 3 BG instruments was shown to be valid compared to a metabolic cart. Instruments are not interchangeable and caution is advised when using this device for assessment of resting metabolic rate especially for women.