Total energy expenditure in healthy ambulatory older adults aged ≥ 80 years - a doubly labelled water study

Introduction: The life expectancy of older adults continue to increase, however knowledge regarding their total energy requirements are lacking. This study aims to compare the total energy expenditure (TEE) of older adults >= 80 years measured using doubly labelled water (DLW), with estimated TEE. The hypothesis was that the Mifflin, Ikeda and Livingston equations will more closely estimate energy requirements than the commonly used Schofield equation. Methods: Resting metabolic rate (RMR) and TEE were measured using the reference methods of indirect calorimetry and doubly labelled water (DLW) respectively. Bland Altman plots compared measured RMR and TEE with predicted RMR using equations (Mifflin, Ikeda, Livingston, Schofield) and predicted TEE (predicted RMR x physical activity level). Results: Twenty-one older adults (age range 80.7-90.1 years, BMI 26.1 +/- 5.5 kg/m2) were included. The Schofield equation demonstrated the greatest bias from measured RMR, overestimating approximately up to double the mean difference (865 +/- 662 kJ/d) compared with the three other equations. The Schofield equation exhibited the greatest bias (over-estimation of 641 +/- 1066 kJ/d) compared with measured TEE. The other three equations under-estimated TEE, with the least bias from Ikeda (37 +/- 1103 kJ/d), followed by Livingston (251 +/- 1108kJ/d) and Mifflin (354 +/- 1140kJ/d). Data are mean +/- SD. Conclusions: In older adults >= 80 years, the Ikeda, Mifflin and Livingston equations provide closer estimates of TEE than the widely used Schofield equation. The development of nutrition guidelines therefore should consider the utilization of equations which more accurately reflect age specific requirements.