The use of a handheld calorimetry unit to estimate energy expenditure during different physiological conditions.

Background: Accurately determining rates of energy expenditure (EE) under free-living conditions is important in understanding the mechanisms involved in the development and prevention of obesity. Metabolic carts are not portable enough for most free-living situations. The purpose of this study was to compare a portable, handheld indirect calorimetry device (HealtheTech Incorporated, Golden, CO) to a metabolic cart (Physio-Dyne Instrument Corporation, Quogue, NY) during 3 different physiologic states.

Methods: EE was measured by both the handheld calorimeter (5-10 minutes) and the metabolic cart (15-20 minutes) in 20 healthy subjects (18-35 years of age). Measurements were made during 3 physiologic states: (1) postabsorptive rest (REE), (2) postprandial rest (fed energy expenditure, FEE), and (3) while walking in place (activity energy expenditure, AEE).

Results: There were no significant differences between the means of the cart vs the hand-held device for REE (mean +/- SE; kcal/d; 1552 +/- 64 vs 1551 +/- 63), FEE (1875 +/- 99 vs 1825 +/- 86), and AEE (3333 +/- 218 vs 3489 +/- 152). The range over which the techniques were tested was 1300-5000 kcal/d. The agreement between the 2 methods was excellent for REE (0.80, p < .0001), FEE (0.89, p < .0001), and AEE (0.75, p < .0002).

Conclusions: Compared with the metabolic cart, the handheld device provided similar estimates of energy expenditure during resting, postprandial, and physically active states. This suggests that portable indirect calorimetry devices can provide reliable and valuable information in free-living research situations for which maximal energy expenditure is <5000 kcal/d.