A New Approach to Improve the Validity of Doubly Labeled Water to Assess CO2 Production during High-Energy Turnover

Abstract

Purpose: Accurate measurement of energy expenditure (EE) using doubly labeled water depends on the estimate of total body water (TBW). The aims of this study were to 1) assess the accuracy of a new approach for estimating TBW and EE during high-energy turnover and 2) assess the accuracy of day-to-day assessment of EE with this new approach. Methods: EE was measured in six healthy subjects (three male) for 5 consecutive days using three doubly labeled water methods: 1) the plateau, 2) slope-intercept, and 3) overnight-slope method, with whole-room indirect calorimetry as reference method. Urine samples were collected every evening and morning. High EE (physical activity level of >2.5) was achieved by cycling 4 h•d −1 . Results: Physical activity level was 2.8 ± 0.1. TBW values were 41.9 ± 6.1, 38.4 ± 5.7, and 40.4 ± 5.8 L for the plateau, slope-intercept, and overnight-slope methods, respectively. The overnight-slope method showed the highest accuracy in estimated CO 2 production, when compared with indirect calorimetry over the complete 5-d period (mean ± SD difference, 0.9% ± 1.6%). The plateau method significantly overestimated CO 2 production by 4.7% ± 2.6%, whereas the slope-intercept method underestimated CO 2 production (−3.4% ± 2.3%). When CO 2 production was assessed per day, the overnight-slope method showed an average difference of 9.4% ± 4.5% to indirect calorimetry. Conclusions: The overnight-slope method resulted in a more accurate estimation of CO 2 production and EE compared with the plateau or slope-intercept method over a 5-d period in high physical activity conditions. Day-to-day determination of EE using the overnight-slope method was more accurate than diet recall and several standard prediction equations in athletes.

Determination of energy expenditure in professional cyclists using power data: Validation against doubly labeled water

“…Moreover, high rates of water turnover were corrected for by decreasing the duration of the observation periods to account for the rapid decline in isotope enrichments 40 . Additionally, we determined the dilution space using an overnight‐slope method that improves the accuracy of DLW measurements in high‐energy turnover conditions (error of <1% compared with indirect calorimetry) 6 . A second limitation to the DLW measurements is that 2 H and 18 O are naturally present in water but their abundances vary depending on geographical location 40 .…”

“…Finally, at the end of the Vuelta, all urine samples were transported to Maastricht University for analysis of the 2 H and 18 O concentrations as described by Plasqui et al 8 Briefly, the urine samples were equilibrated with H 2 and CO 2 gases, after which the enrichment of the two gases was measured by isotope ratio mass spectrometry 17 . The isotope dilution spaces were calculated from the urine samples using the overnight‐slope method as this has been shown to be most accurate in high‐energy turnover conditions 6 . CO 2 production was then calculated using an updated equation of CO 2 ‐production, 4 whereas EE was determined using Weirs non‐protein equation, while assuming a respiratory quotient of 0.90 since this best reflects the high carbohydrate consumption of these athletes 7 .…”

“…Doubly labeled water 4 is considered the gold‐standard method to determine EE over longer time periods (e.g., multiple days) in free‐living conditions 5,6 . Previous studies that used DLW to quantify EE during the Tour de France and Giro d'Italia (two 3‐week cycling events) observed average total daily energy expenditure (TDEE) values of 33.7 and 32.3 MJ/day, respectively 7,8 .…”

“…Doubly labeled water 4 is considered the gold-standard method to determine EE over longer time periods (e.g., multiple days) in free-living conditions. 5,6 Previous studies that used DLW to quantify EE during the Tour de France and Giro d'Italia (two 3-week cycling events) observed average total daily energy expenditure (TDEE) values of 33.7 and 32.3 MJ/day, respectively. 7,8 Although knowledge of the typical TDEE is important for nutrition prescription, the variability in EE between different athletes and between different competitions limit the use of these generic estimates for nutritional prescription in practice.…”

“…(1) 6 | Statistical analysis SPSS (IBM SPSS Statistics for Windows, Version 25.0; IBM Corp.) was used for all statistical analyses unless stated otherwise. The level for statistical significance was set at p < 0.05.…”