The agreement between the MedGem® indirect calorimeter and a standard indirect calorimeter in anorexia nervosa

Abstract

Measurement of the basal metabolic rate (BMR) can be used to estimate the calories required for weight gain during refeeding in anorexia nervosa (AN). The reference method for measuring the BMR is indirect calorimetry. MedGem has developed a new indirect calorimeter that calculates the metabolic rate much more quickly than standard indirect calorimeters. This study compared the BMR measured by the MedGem and standard indirect calorimetry in an AN population. We measured the BMR using the Deltatrac metabolic cart followed immediately by the MedGem indirect calorimeter in 27 subjects (12 patients and 15 controls). Bland-Altman plots show that there is poor agreement between the BMR reported by the MedGem compared to the Deltatrac. Until better agreement with standard indirect calorimetry can be shown the MedGem should not be used for calorimetry in AN. Possible factors that may limit the MedGem's reliability include patient discomfort with the mouthpiece, use of a fixed RQ, and the short sampling period.