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

Background and aims 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. Methods 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. Results 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 ± 64 ml/min, p = 0.114) nor REE (MedGem: 1963 ± 437 vs. metabolic cart: 2047 ± 440 kcal/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 336 kcal/day), which was similar to predictive equations. Conclusions 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.