The use of whole body calorimetry to compare measured versus predicted energy expenditure in postpartum women

Abstract

Background Accurate assessment of energy expenditure may support weight-management recommendations. Measuring energy expenditure for each postpartum woman is unfeasible; therefore, accurate predictive equations are needed. Objectives This study compared measured with predicted resting energy expenditure (REE) and total energy expenditure (TEE) in postpartum women. Methods This was a longitudinal observational study. REE was measured at 3 mo postpartum (n = 52) and 9 mo postpartum (n = 49), whereas TEE was measured once at 9 mo postpartum (n = 43) by whole body calorimetry (WBC). Measured REE (REEWBC) was compared with 17 predictive equations; measured TEE plus breast milk energy output (ERWBC) was compared with the estimated energy requirements/Dietary Reference Intakes equation (EERDRI). Fat and fat-free mass were measured by dual-energy X-ray absorptiometry. Group-level agreement was assessed by the Pearson correlation, paired t test, and Bland-Altman (bias) analyses. Individual-level accuracy was assessed with the use of Bland-Altman limits of agreement, and by the percentage of women with predicted energy expenditure within 10% of measured values (“accuracy”). Results The cohort was primarily Caucasian (90%). At a group level, the best equation predicting REEWBC was the DRI at 3 mo postpartum (–7 kcal, –0.1%; absolute and percentage bias, respectively), and the Harris-Benedict at 9 mo postpartum (–17 kcal, –0.5%). At an individual level, the Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU) height and weight equation was the most accurate at 3 mo postpartum (100% accuracy) and 9 mo postpartum (98% accuracy), with the smallest limits of agreement. Equations including body composition variables were not more accurate. Compared with ERWBC, EERDRI bias was –36 kcal, with inaccurate predictions in 33% of women. Conclusions Many REE predictive equations were accurate for group assessment, with the FAO/WHO/UNU height and weight equation having the highest accuracy for individuals. EERDRI performed well at a group level, but inaccurately for 33% of women. A greater understanding of the physiology driving energy expenditure in the postpartum period is needed to better predict TEE and ultimately guide effective weight-management recommendations.

Predictive equations for estimating resting energy expenditure in women with overweight and obesity at three postpartum stages

“…In agreement with other studies (11,33) , the FFM-based equations did not markedly improve accuracy compared with the weight-based equations. The overall performance of both Lazzer FFM and Johnstone FFM cannot with certainty be considered superior to the overall performance of Henry WH30−60 ; thus, we do not consider it necessary to use an FFM-based equation for postpartum women when dual-energy X-ray absorptiometry is used to determine FFM.…”

“…Pereira et al . (11) found similar patterns for performance of equations in BMI-specific categories, however, with larger individual variation in REE (increasing limits of agreement) with increasing BMI (11) .…”

“…Our results are in better agreement with Pereira et al . (11) who found a number of equations with more than 80 % accurate predictions at 3 months postpartum, including one with 100 % (FAO/WHO/United Nations University (FAO/WHO/UNU), height and weight). We did not report here the results from FAO/WHO/UNU from 1985; however, we report the updated versions of these, the Schofield equations, which were not among the overall six best performing equations in our population.…”

“…Unlike Pereira et al . (11) , we did not stratify and perform BMI group-specific analyses. However, there was a large shift in BMI categories over the postpartum period due to diet treatment.…”

“…This may lead to an overestimation of the energy requirement. To our knowledge, only two publications have previously validated existing predictive equations in women postpartum at 1–10 d (10) and 3 months and 9 months postpartum, respectively (11) . Both studies were only observational and included both lactating and non-lactating women of several BMI categories.…”