Research and Development Foundation of Rio de Janeiro State (FAPERJ)Programa Pesquisa para o SUSCoordination of Improvement of Higher Education Personnel (CAPES/Brazil)Background and aims: Precise evaluation of resting metabolic rate (RMR) is critical, especially for seniors in syndromes conditions. The study aimed to compare different methods and devices to evaluate the resting metabolic rate and assess them’ reliability in Brazilian women with metabolic syndrome. Methods: A single-center prospective study with forty elderly postmenopausal women was performed to verify the reliability of indirect calorimetry (IC) versus Bioimpedance (BIA) on RMR fluctuations for an interval length of six months. Results: Measurements showed a high correlation between devices at baseline [BIA vs IC, intraclass correlation coefficient (ICC) ¼ 0.906 (0.822e0.950)]. Surprisingly, a high correlation was kept between BIA and IC after six months [BIA vs. IC, ICC ¼ 0.909 (0.829e0.952)]. The results suggest that both BIA and IC are excellent strategies to measure RMR in elderly postmenopausal women and with metabolic syndrome. Conclusions: However, the BIA method presents greater convenience, optimizes patients’ time, and does not require prolonged fasting to obtain good reliable results compared to IC.