Equations for predicting the energy requirements of healthy adults aged 18-81 y

Recent studies have questioned the accuracy of using the current recommended dietary allowances (RDAs) to predict usual energy requirements in adults.

We developed equations to predict adult energy requirements from simple anthropometric and laboratory measures by using the doubly labeled water method to determine each subject's total energy expenditure (TEE), which is equal to usual energy requirements in weight-stable individuals.

This was a cross-sectional study conducted with 93 healthy, free-living adults [44 men and 49 women; body mass index range (in kg/m2): 18.4-31.8] aged 18-81 y. Body fat and fat-free mass were measured by underwater weighing, physical activity was estimated by using activity monitors, and resting energy expenditure was determined by indirect calorimetry. Information on anthropometric variables and reported strenuous activity was also collected.

Three regression equations were developed and verified for accuracy by using bootstrap analysis and doubly labeled water data published by other research groups. The first equation used information on only age, weight, height, and sex and had an SEE for prediction of TEE of 1.80 MJ/d. The second and third equations used different combinations of basic and laboratory data and had SEEs of 1.55 and 1.65 MJ/d, respectively. With use of the same analytic approaches, the RDAs for energy were shown to significantly underestimate usual energy needs by approximately 10%; the extent of underestimation was significantly greater for subjects with high TEEs than for subjects with low TEEs.

Regression equations based on doubly labeled water measurements of TEE appear to be more accurate than the current RDAs for predicting energy requirements in healthy, nonobese adults living in affluent countries.