Accuracy of the MedGem® portable indirect calorimeter for measuring resting energy expenditure in adults with class II or III obesity

Abstract

The accuracy of some portable indirect calorimeters in estimating resting energy expenditure (REE) - and hence energy recommendations - among pre-bariatric patients is unknown. Our objective was to assess the accuracy of the MedGem® among individuals with class II or III obesity awaiting bariatric surgery. Male and female adults who were awaiting bariatric surgery were recruited to this cross-sectional study. MedGem-derived oxygen consumption (O2) and REE were compared to O2 and REE from a metabolic cart. REE was also calculated using several common equations to assess the clinical utility of this portable tool. Body composition was assessed by dual energy X-Ray absorptiometry. Paired t-test and Bland-Altman analysis (expressed as bias [average difference] and limits of agreement [bias±2 standard deviations]) evaluated O2 and REE accuracy. Twenty-six individuals were included (34±9 years old; n = 20, 76.9% female), with the majority (n=15, 57.7%) having class II obesity. Neither O2 (MedGem: 283±63 vs. metabolic cart: 293±64ml/min, p=0.114) nor REE (MedGem: 1963±437 vs. metabolic cart: 2047±440kcal/day, p=0.057) were different between devices. Body composition did not relate to bias. The MedGem had wide limits of agreement for REE (-504 to 336kcal/day), which was similar to predictive equations. Although REE from the MedGem was not different than REE from the metabolic cart, individual-level accuracy was poor and similar to predictive equations in patients with class II or III obesity. Nonetheless, efficacy of repeated assessments during weight loss warrant future investigation.