To measure or to estimate? A comparison between indirect calorimetry and predictive equations for resting metabolic rate in institutionalized older adults: a systematic review.

INTRODUCTION: Population aging and institutionalization require accurate energy estimates for the maintenance of health and vitality. Resting Metabolic Rate (RMR) is frequently estimated using predictive equations; however, their accuracy in institutionalized older adults remains uncertain, which may compromise nutritional management and worsen clinical outcomes. OBJECTIVE: To systematically evaluate the accuracy of RMR predictive equations compared to the gold standard of indirect calorimetry in residents of Long-Term Care Facilities (LTCFs). METHODS: A systematic review was conducted in accordance with the PRISMA guidelines and registered in PROSPERO. Observational studies comparing measured and estimated RMR in LTCFs residents were included. Methodological quality and the strength of evidence were assessed using the QUADAS-2 and GRADE instruments. RESULTS: Four studies (n == 332) were included. Most of the analyzed equations (79%) showed a tendency to overestimate RMR at the group level. Individual accuracy was considered low, not exceeding 41%. The Lührmann equation demonstrated acceptable performance and moderate quality of evidence, whereas classic formulas, such as Harris-Benedict and FAO/WHO/UNU, showed low accuracy. No equation achieved exceptional performance. CONCLUSION: Most predictive equations overestimate RMR in this population, which can lead to errors in dietary prescription and promote adverse metabolic outcomes in LTCF s residents. Indirect calorimetry should be prioritized. In its absence, estimation using equations should be performed with caution, recognizing the low accuracy of traditional formulas and the need for clinical monitoring to prevent nutritional imbalances.