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.
Keywords: Indirect calorimetry; Nutrition support; Obese; Overweight; Portable device; RMR; Resting metabolic rate.
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