Doubly Labeled Water Measurements Research Articles

Total Energy Expenditure, Body Composition, Physical Activity, and Step Count in Japanese Preschool Children: A Study Based on Doubly Labeled Water.

Adequate energy intake is essential for the healthy development of children, and the estimated energy requirement of children is determined by total daily energy expenditure (TDEE) and energy deposition for growth. A previous study in Japanese tweens indicated that TDEE could be estimated by fat-free mass (FFM) and step count. The aims of this study were to measure TDEE in Japanese preschool children and to confirm whether TDEE can be estimated by FFM and step count in preschool children. Twenty-one children aged 4–6 years old (11 girls and 10 boys; age, 5.1 (0.9) years; height, 107.2 (6.6) cm; weight, 17.5 (1.7) kg; BMI, 15.3 (1.3); mean (SD)) participated in this study. FFM and 7-day TDEE were obtained by doubly labeled water (DLW). Participants wore accelerometers during the DLW measurement period. No significant differences were observed in age-adjusted height, weight, BMI, FFM (13.0 (1.5) kg), or TDEE (1300 (174) kcal/day) between girls and boys. Girls had significantly higher percent fat and a lower daily step count than boys. Stepwise regression analysis revealed that FFM and step count were significant predictors of TDEE; TDEE (kcal/day) = 85.0 × FFM (kg) + 0.0135 × step count (steps/day). This accounted for 74% of TDEE variance. The current study confirmed that FFM and step count are major determinants of TDEE in Japanese preschool children as well as adolescents, although further research is needed to obtain precise equations.

Maximizing precision and accuracy of the doubly labeled water method via optimal sampling protocol, calculation choices, and incorporation of 17O measurements.

BackgroundThe doubly-labeled water (DLW) method is the gold standard methodology for determination of free-living, total daily energy expenditure (TEE). However, there is no single accepted approach for either the sampling protocols (daily vs. two-point, in which samples are collected after dosing and at the end of the measurement period) or the calculations used in the determination of the rate of carbon dioxide production (rCO2) and TEE. Moreover, fluctuations in natural background abundances introduce error in the calculation of rCO2 and TEE. The advent of new technologies makes feasible the possibility of including additional isotope measures (17O) to account for background variation, which may improve accuracy.MethodsSixteen subjects were studied for 7 consecutive days in a whole-room indirect calorimeter (IC) with concurrent measurement of TEE by DLW. Daily urine samples were obtained and isotope ratios determined using off-axis integrated cavity output spectroscopy (OA-ICOS).ResultsWe determined the best combination of approaches for estimating dilution spaces, elimination rates, and calculated average daily carbon dioxide production (VCO2) using six different published equations. Using the best combination, multi-point fitting of isotope elimination rates using the daily urine samples substantially improved the average precision (4.5% vs. 6.0%) and accuracy (−0.5% vs. −3.0%) compared with the two-point method. This improvement may partly reflect the less variable day-to-day chamber measurements of energy expenditure. Utilizing 17O measurements to correct for errors due to background isotope fluctuations provided additional but minor improvements in precision (4.2% vs. 4.5%) and accuracy (0.2% vs. 0.5%).ConclusionsThis work shows that optimizing sampling and calculation protocols can improve the accuracy and precision of DLW measurements.

Methodologic considerations for measuring energy expenditure differences between diets varying in carbohydrate using the doubly labeled water method

Low-carbohydrate diets have been reported to significantly increase human energy expenditure when measured using doubly labeled water (DLW) but not by respiratory chambers. Although DLW may reveal true physiological differences undetected by respiratory chambers, an alternative possibility is that the expenditure differences resulted from failure to correctly estimate the respiratory quotient (RQ) used in the DLW calculations. To examine energy expenditure differences between isocaloric diets varying widely in carbohydrate and to quantitatively compare DLW data with respiratory chamber and body composition measurements within an energy balance framework. DLW measurements were obtained during the final 2 wk of month-long baseline (BD; 50% carbohydrate, 35% fat, 15% protein) and isocaloric ketogenic diets (KD; 5% carbohydrate, 80% fat, 15% protein) in 17 men with a BMI of 25-35 kg/m2. Subjects resided 2 d/wk in respiratory chambers to measure energy expenditure (EEchamber). DLW expenditure was calculated using chamber-determined RQ either unadjusted (EEDLW) or adjusted (EEDLWΔRQ) for net energy imbalance using diet-specific coefficients. Accelerometers measured physical activity. Body composition changes were measured by dual-energy X-ray absorptiometry (DXA) which were combined with energy intake measurements to calculate energy expenditure by balance (EEbal). After transitioning from BD to KD, neither EEchamber nor EEbal were significantly changed (∆EEchamber=24±30 kcal/d; P=0.43 and ∆EEbal=-141±118 kcal/d; P=0.25). Similarly, physical activity (-5.1±4.8%; P=0.3) and exercise efficiency (-1.6±2.4%; P=0.52) were not significantly changed. However, EEDLW was 209±83 kcal/d higher during the KD (P=0.023) but was not significantly increased when adjusted for energy balance (EEDLWΔRQ=139±89 kcal/d; P=0.14). After removing 2 outliers whose EEDLW were incompatible with other data, EEDLW was marginally increased during the KD by 126±62 kcal/d (P=0.063) and EEDLW∆RQ was only 46±65 kcal/d higher (P=0.49). DLW calculations failing to account for diet-specific energy imbalance effects on RQ erroneously suggest that low-carbohydrate diets substantially increase energy expenditure. This trial was registered at clinicaltrials.gov as NCT01967563.

Physical Activity Assessment with the ActiGraph GT3X and Doubly Labeled Water.

To compare the degree to which four accelerometer metrics-total activity counts per day (TAC per day), steps per day (steps per day), physical activity energy expenditure (PAEE) (kcal·kg·d), and moderate- to vigorous-intensity physical activity (MVPA) (min·d)-were correlated with PAEE measured by doubly labeled water (DLW). Additionally, accelerometer metrics based on vertical axis counts and triaxial counts were compared. This analysis included 684 women and 611 men age 43 to 83 yr. Participants wore the Actigraph GT3X on the hip for 7 d twice during the study and the average of the two measurements was used. Each participant also completed one DLW measurement, with a subset having a repeat. PAEE was estimated by subtracting resting metabolic rate and the thermic effect of food from total daily energy expenditure estimated by DLW. Partial Spearman correlations were used to estimate associations between PAEE and each accelerometer metric. Correlations between the accelerometer metrics and DLW-determined PAEE were higher for triaxial counts than vertical axis counts. After adjusting for weight, age, accelerometer wear time, and fat free mass, the correlation between TAC per day based on triaxial counts and DLW-determined PAEE was 0.44 in women and 0.41 in men. Correlations for steps per day and accelerometer-estimated PAEE with DLW-determined PAEE were similar. After adjustment for within-person variation in DLW-determined PAEE, the correlations for TAC per day increased to 0.61 and 0.49, respectively. Correlations between MVPA and DLW-determined PAEE were lower, particularly for modified bouts of ≥10 min. Accelerometer measures that represent total activity volume, including TAC per day, steps per day, and PAEE, were more highly correlated with DLW-determined PAEE than MVPA using traditional thresholds and should be considered by researchers seeking to reduce accelerometer data to a single metric.

The Relationship Between Accelerometer-measured Sedentary Behaviors And Physical Activity Energy Expenditure Measured By Doubly-labeled Water

PURPOSE: The aim was to study the association between accelerometer determined total sedentary time (ST) and breaks in ST with physical activity energy expenditure (PAEE) from doubly-labeled water (DLW). Further, results based on accelerometer counts from only the vertical axis (VT) and from all three axes (VM3) were compared. METHODS: Data from 748 women and 659 men (43-83 years) were analyzed. Participants wore the Actigraph GT3X accelerometer on the hip during waking hours for seven days twice during the study about 6 months apart. Using the average of the two measurements, total ST was estimated using cut-points of 100 (VT) and 200 (VM3) counts/min. A break in ST was defined as at least one minute of a higher activity count within a sedentary bout. PAEE (kcal/day) was estimated by subtracting resting metabolic rate and the thermic effect of food from total energy expenditure derived from one DLW measurement, with a small subsample having a repeat. Partial Spearman correlations and linear regression models were used to determine associations between total ST and breaks per sedentary hour with PAEE. Correlations and models were adjusted for age, weight, fat free mass, accelerometer wear time and moderate-to-vigorous physical activity (MVPA). RESULTS: Mean total ST using VT and VM3 were 9.0 and 7.9 h/day of wear time, respectively, in women and 9.3 and 8.5 h/day in men. Corresponding mean breaks per sedentary hour were 10.4 and 11.0 in women and 9.2 and 9.4 in men. Partial Spearman correlation coefficients between ST and PAEE ranged from -0.34 to -0.44 and correlations between breaks per sedentary hour and PAEE from 0.27 to 0.34. After adjustment for within-person variation in PAEE, correlations for ST ranged from -0.38 to -0.68 and correlations for breaks per sedentary hour from 0.35 to 0.51. In adjusted models, each hour of ST was associated with lower PAEE (β= -66 to -103 kcal, p < .0001) and each break per sedentary hour was associated with higher PAEE (β= 21 to 39 kcal, p < .0001). Estimates were slightly higher for VT vs. VM3. CONCLUSIONS: This study found that total ST was inversely associated and breaks in ST was positively associated with PAEE in both men and women independent of body composition and MVPA. Replacing ST with light physical activity and more frequent movement throughout the day may have an impact on an individual’s PAEE.

Seasonal variation in natural abundance of 2H and 18O in urine samples from rural Nigeria.

The doubly labeled water (DLW) method is used to measure free-living energy expenditure in humans. Inherent to this technique is the assumption that natural abundances of stable isotopes (2)H and (18)O in body water remain constant over the course of the measurement period and after elimination of the loading dose of DLW will return to the same predose level. To determine variability in the natural abundances of (2)H and (18)O in humans living in a region with seasonal shifts in rain patterns and sources of drinking water, over the course of 12 mo we collected weekly urine samples from four individuals living in southwest Nigeria as well as samples of their drinking water. From ongoing regional studies of hypertension, obesity, and energy expenditure, we estimated average water turnover rate, urine volumes, and sodium and potassium excretion. Results suggest that (2)H and (18)O in urine, mean concentrations of urinary sodium and potassium, urine volume, and total body turnover differed significantly from dry to rainy season. Additionally, seasonal weather variables (mean monthly maximum temperatures, total monthly rainfall, and minimum relative humidity) were all significantly associated with natural abundances in urine. No seasonal difference was observed in drinking water samples. Findings suggest that natural abundances in urine may not remain constant as assumed, and studies incorporating DLW measurements across the transition of seasons should interpret results with caution unless appropriate doses of the tracers are used.

Inter- and intraindividual correlations of background abundances of 2H, 18O and 17O in human urine and implications for DLW measurements

The method of choice for measuring total energy expenditure in free-living individuals is the doubly labeled water (DLW) method. This experiment examined the behavior of natural background isotope abundance fluctuations within and between individuals over time to assess possible methods of accounting for variations in the background isotope abundances to potentially improve the precision of the DLW measurement. In this work, we measured natural background variations in (2)H, (18)O and (17)O in water from urine samples collected from 40 human subjects who resided in the same geographical area. Each subject provided a urine sample for 30 consecutive days. Isotopic abundances in the samples were measured using Off-Axis Integrated Cavity Output Spectroscopy. Autocorrelation analyses demonstrated that the background isotopes in a given individual were not temporally correlated over the time scales of typical DLW studies. Using samples obtained from different individuals on the same calendar day, cross-correlation analyses demonstrated that the background variations of different individuals were not correlated in time. However, the measured ratios of the three isotopes (2)H, (18)O and (17)O were highly correlated (R(2)=0.89-0.96). Although neither specific timing of DLW water studies nor intraindividual comparisons were found to be avenues for reducing the impact of background isotope abundance fluctuations on DLW studies, strong inter-isotope correlations within an individual confirm that use of a dosing ratio of 8‰:1‰ (0.6 p.p.m.: p.p.m.) optimizes DLW precision. Theoretical implications for the possible use of (17)O measurements within a DLW study require further study.

Special Considerations for Measuring Energy Expenditure with Doubly Labeled Water under Atypical Conditions.

The global increase in the prevalence of obesity has dramatically increased interest in understanding the factors that influence human total energy expenditure (TEE). This in turn has increased interest in the doubly labeled water (DLW) method, a technique for measurement of total energy expenditure in free-living humans. The increasing use of this method is attributed to its portability, objectivity, minimal invasiveness, high accuracy and good precision. Although a relatively standard protocol for the method has emerged, the new generation of users often is unfamiliar with rationale behind aspects of the protocol as well as the approaches to avoid or correct for in situations that are not covered by the standard protocol procedure. The primary uncommon situations like introduction of isotopically different diet and fluids with or without geographical relocation, seasonal and temperature variations, activity level of participants etc. during or prior to the DLW measurements can lead to shift in baseline abundance of 2H and 18O or tracer elimination, resulting in moderate to large errors in the measured TEE. These unique situations call for special modifications to the conventional protocol to minimize errors. The objective of the present review was to assemble a list of frequently asked questions and the issues they represent, and then examine the available literature to describe and explain the modifications to the standard DLW protocol to maintain the method’s accuracy. This discussion of DLW protocol modification can be an excellent resource for investigators who intend to use this measurement technique for interesting and uncommon study designs.

Association between smoking and total energy expenditure in a multi-country study

BackgroundThe association between smoking and total energy expenditure (TEE) is still controversial. We examined this association in a multi-country study where TEE was measured in a subset of participants by the doubly labeled water (DLW) method, the gold standard for this measurement.MethodsThis study includes 236 participants from five different African origin populations who underwent DLW measurements and had complete data on the main covariates of interest. Self-reported smoking status was categorized as either light (<7 cig/day) or high (≥7 cig/day). Lean body mass was assessed by deuterium dilution and physical activity (PA) by accelerometry.ResultsThe prevalence of smoking was 55% in men and 16% in women with a median of 6.5 cigarettes/day. There was a trend toward lower BMI in smokers than non-smokers (not statistically significant). TEE was strongly correlated with fat-free mass (men: 0.70; women: 0.79) and with body weight (0.59 in both sexes). Using linear regression and adjusting for body weight, study site, age, PA, alcohol intake and occupation, TEE was larger in high smokers than in never smokers among men (difference of 298 kcal/day, p = 0.045) but not among women (162 kcal/day, p = 0.170). The association became slightly weaker in men (254 kcal/day, p = 0.058) and disappeared in women (−76 kcal/day, p = 0.380) when adjusting for fat-free mass instead of body weight.ConclusionThere was an association between smoking and TEE among men. However, the lack of an association among women, which may be partly related to the small number of smoking women, also suggests a role of unaccounted confounding factors.

Misreporting of Energy Intake in the Elderly Using Doubly Labeled Water to Measure Total Energy Expenditure and Weight Change

Background: One of the major problems in dietary assessment is inaccuracy in reporting diet.Objective: To examine the association between self-reported energy intake (EI) by food frequency questionnaire (FFQ) and energy expenditure (EE), measured by doubly labeled water (DLW), among older persons.Design: EE was assessed in 298 high-functioning, community-dwelling older adults (70–79 years of age) over a 2-week period using DLW. Dietary intake was assessed using a Block FFQ. The ratio between reported EI and total energy expenditure (TEE) was calculated. Misreporting was defined as follows: participants with an EI/TEE ratio of <0.77 were categorized as low energy reporters, while participants with an EI/TEE ratio >1.28 were categorized as high energy reporters. Participants with an EI/TEE ratio of 0.77–1.28 were categorized as “true” energy reporters. One-year percent weight change prior to EE visit was used as another validation indicator. Participants who were low energy reporters but lost >2% of their body weight were categorized as undereaters.Results: Two hundred ninety-six participants provided both FFQ and DLW measurements. Forty-three percent of participants were low energy reporters; among them, almost 30% lost weight and, therefore, were categorized as undereaters. The undereaters consumed significantly fewer calories. No difference in the frequency of low energy reporting was detected between genders or racial groups. Underreporters had significantly higher body weight than “true” or high reporters. Undereaters tended to have higher body mass index than the underreporters.Conclusions: Undereating is prevalent in the elderly and may be falsely perceived as underreporting. It should be further addressed and characterized in future studies.

Assessment of the physical activity level with two questions: validation with doubly labeled water

To validate a two-question questionnaire on physical activity with the doubly labeled water (DLW) method. Cross-sectional study. Nine volunteers, age 33-75 years, with a mean body mass index (BMI) (kg m(-2)) of 27.4. A questionnaire with one question on physical activity at work and one question on physical activity during leisure time. The answers were converted into a PAL (physical activity level=energy expenditure/basal metabolic rate) value, which was validated with the DLW method. The mean values (s.d.) of PAL for the questionnaire and DLW measurements were 1.7 (0.1) and 1.7 (0.1), respectively, with a mean difference of 0.004 (0.172). The results were promising to the extent that they could be used in large-scale epidemiological studies.

Ontogeny of oxygen stores and physiological diving capability in Australian sea lions

1 For air-breathing animals in aquatic environments, foraging behaviours are often constrained by physiological capability. The development of oxygen stores and the rate at which these stores are used determine juvenile diving and foraging potential. 2 We examined the ontogeny of dive physiology in the threatened Australian sea lion Neophoca cinerea. Australian sea lions exploit benthic habitats; adult females demonstrate high field metabolic rates (FMR), maximize time spent near the benthos, and regularly exceed their calculated aerobic dive limit (cADL). Given larger animals have disproportionately greater diving capabilities; we wanted to determine the extent physiological development constrained diving and foraging in young sea lions. 3 Ten different mother/pup pairs were measured at three developmental stages (6, 15 and 23 months) at Seal Bay Conservation Park, Kangaroo Island, South Australia. Hematocrit (Hct), haemoglobin (Hb) and plasma volume were analyzed to calculate blood O2 stores and myoglobin was measured to determine muscle O2. Additionally, FMR's for nine of the juveniles were derived from doubly-labelled water measurements. 4 Australian sea lions have the slowest documented O2 store development among diving mammals. Although weaning typically occurs by 17·6 months, 23-month juveniles had only developed 68% of adult blood O2. Muscle O2 was the slowest to develop and was 60% of adult values at 23 months. 5 We divided available O2 stores (37·11 ± 1·49 mL O2 kg−1) by at-sea FMR (15·78 ± 1·29 mL O2 min−1 kg−1) to determine a cADL of 2·33 ± 0·24 min for juvenile Australian sea lions. Like adults, young sea lions regularly exceeded cADL's with 67·8 ± 2·8% of dives over theoretical limits and a mean dive duration to cADL ratio of 1·23 ± 0·10. 6 Both dive depth and duration appear impacted by the slow development of oxygen stores. For species that operate close to, or indeed above their estimated physiological maximum, the capacity to increase dive depth, duration or foraging effort would be limited. Due to reduced access to benthic habitat and restricted behavioural options, young benthic foragers, such as Australian sea lions, would be particularly vulnerable to resource limitation.

Using doubly-labeled water measurements of human energy expenditure to estimate inhalation rates

Doubly-labeled water (DLW) data is recognized as an improvement over alternative methods to quantify human energy expenditure. Previously, energy expenditure has been estimated indirectly using heart-rate monitoring, calorimetry, or accelerometer measurements. Inhalation rate estimates can benefit from improved energy expenditure estimates using equations developed by Layton. DLW methods are advantageous for several reasons: the database is robust, they are direct measures, subjects are free-living, and the observation period is longer than what is possible from staged activity measures. DLW energy data is an improvement over previous inhalation estimates based on dietary recall survey data. Mean long-term inhalation rates of 16 m3/day and 13 m3/day, for physically active adult men and women, respectively, were derived based on DLW estimates of energy expended. The range of human energy expenditure is narrow with the maximum energy expenditure not likely greater than twice the minimum.

Affordable measurement of human total energy expenditure and body composition using one-tenth dose doubly labelled water

The doubly labelled water (DLW) method is the technique of choice for measurement of free-living total energy expenditure (TEE) in humans. A major constraint on the clinical applicability of the method has been the expense of the (18)O isotope. We have used a reduced-dose (one-tenth of the currently recommended standard dose) of DLW for the measurement of TEE and body composition in nine healthy adult male volunteers. TEE measured by reduced-dose DLW was positively correlated with resting energy expenditure measured by metabolic cart (r=0.87, P<0.01). Isotope-derived fat mass and body mass index were strongly correlated (r=0.86, P<0.01). In four subjects in whom we performed a complementary evaluation using standard-dose isotope enrichment, the TEE measurements were satisfactorily comparable (mean+/-s.d.: reduced dose 2586+/-155 kcal/day vs standard dose 2843+/-321 kcal/day; mean difference 257+/-265 kcal/day). These data indicate that DLW measurements of human energy expenditure and body composition can be performed at a substantially reduced dose (and cost) of isotope enrichment than is currently employed.

Physiological Daily Inhalation Rates for Free-Living Individuals Aged 2.6 Months to 96 Years Based on Doubly Labeled Water Measurements: Comparison with Time-Activity-Ventilation and Metabolic Energy Conversion Estimates

ABSTRACT In the first part of this article, a critical review of traditional approaches used to estimate daily inhalation rates as a function of age for health risk assessment purposes shows that such rates are not totally reliable due to various biases introduced by both quantitative and qualitative deficiencies regarding certain input parameters. In the second part, the magnitude of under- and overestimations of published inhalation rates derived from each approach is described by a comparison with new sets of physiological daily inhalation rates and distribution percentile values based on total daily energy expenditures (TDEEs) measured by the doubly labeled water (DLW) method. TDEEs are derived from the analysis of deuterium (2H) and heavy oxygen-18 (18O) in urine samples by gas-isotope-ratio mass spectrometry during an aggregate period of over 20,000 days for unrestrained free-living normal-weight individuals aged 2.6 months to 96 years (n = 1252). Regarding physiological values based on DLW measurements, opposite tendencies have been observed between two sets of estimates using time-activity patterns both biased by conservative input data assumptions during sleep and light activities: most estimates based on the time-activity-ventilation approach are overestimated, whereas most of those using metabolic equivalent approach are underestimated. Erroneous food intakes have clearly lead to underestimated rates when used in daily food-energy intake (EFD) and Parameter A approaches. With the latter approach, overestimated basal metabolic rates (BMRs) used in EFD/BMR ratios contribute to the underestimation of inhalation values. Few mean daily inhalation rates and Monte Carlo simulation percentiles based on traditional approaches (57 out of 253) are close to physiological values within a gap of ± 5% or less. Aggregate errors in all estimates (in m3/day and m3/kg-day) vary from -52 to +126%. The most accurate daily inhalation rates are those based on DLW measurements with an error of about ± 5%, as calculated in previous studies for free-living males and females aged 1 month to 96 years and pregnant and lactating adolescents and women aged 11 to 55 years during real-life situations in their normal surroundings.

Energy requirements of children and adolescents

Total energy expenditure (TEE) was calculated at 1-18 years of age from measurements with doubly labelled water (DLW) in 483 boys and 646 girls, and heart rate monitoring (HRM) in 318 boys and 162 girls. Studies on obese, underweight and stunted groups were not included. TEE of populations with different lifestyles was estimated by factorial calculations in 42 studies on time allocation involving 1982 boys and 1969 girls in developed industrialised countries, and 1236 boys and 1116 girls in developing countries. Quadratic polynomial models were best to predict TEE in boys (TEE(MJ day(-1)) = 1.298 + 0.265 kg - 0.0011 kg2, r = 0.982, SEE = 0.518) and girls (TEE(MJ day(-1)) = 1.102 + 0.273 kg - 0.0019 kg2, r = 0.955, SEE = 0.650). TEE at 1-2 years was reduced by 7% based on DLW measurements and TEE estimates of infants. Energy requirements (ER) were calculated adding 8.6 kJ (2 kcal) for each gram of weight gained during growth. Compared with the 1985 FAO/WHO/UNU values, ER were 18-20% lower from 1 to 7 years of age, 12% lower for boys and 5% lower for girls at 7-10 years, and 12% higher for either gender from 12 years onwards. Differences between industrialised and developing countries, the variance in DLW and HRM studies, and the standard error of the estimate (SEE) of the quadratic predictive equations, suggested that ER should be adjusted after 5 years of age by +/-15% in populations with more or less physical activity than an average lifestyle. Physical activity recommendations must accompany dietary recommendations in order to maintain optimal health and reduce the risk of diseases associated with sedentary lifestyles.

Comparison of Different Approaches for the Calculation of Energy Expenditure Using Doubly Labeled Water in a Small Mammal

The doubly labeled water (DLW) method is an isotope-based technique for the estimation of the CO(2) production, and hence energy expenditure, of free-living animals and humans. Several methods are available for the calculation of CO(2) production from the isotope fluxes, depending on different assumptions about the behavior of isotopes during the elimination process. We used the DLW method to estimate the daily energy expenditures (DEE) of 55 field voles (Microtus agrestis) held in a captive facility at 8 degrees C. We calculated DEE using both plateau and intercept approaches for estimating the sizes of the isotope dilution spaces, three different assumptions about fractionation processes, and two ways of treating the different dilution spaces of the oxygen and hydrogen isotopes. We compared the resultant DEE estimates with metabolizable energy intake (MEI) measured during a 3-d feeding trial immediately before the DLW measurements, during which the animals were in energy balance. By making different assumptions about the apparent energy absorption efficiency, we generated a range of direct estimates of MEI. When we compared DEE and MEI, we found that the two-pool model formulations consistently underestimated energy demands by up to 29.8%, depending on the assumptions made in the reference calculation. However, while our data suggest that some correction for fractionation is necessary, with the present data we were unable to separate the two most common treatments of fractionation. These data strongly support the previous suggestion that for small mammals single-pool models provide more accurate estimates of energy demands than two-pool formulation of the DLW method.

長期の運動習慣を有する中年女性におけるエネルギー消費量, 体組成および最大酸素摂取量

The purpose of this study was to examine the effects of long-term habitual exercise on daily total energy expenditure (TEE) and its components, body composition and maximal oxygen uptake (VO2max) in middle-aged Japanese women. Twenty-eight subjects aged 39 to 58 years were assigned either to a nonhabitual exercise group (Control ; n=12) or a habitual exercise group (Exercise ; n=16). TEE, physical activity level (PAL) and the daily physical activity energy expenditure (PAEE) were assessed by doubly labeled water (DLW) method. The exercise-induced energy expenditure (ExEE) and nonexercise-induced energy expenditure (NExEE) were evaluated based on the activity record investigation conducted simultaneously during the DLW measurement period. The result follows that TEE was significantly (p<0.01) higher in the Exercise group (2520 kcal · day-1) than in the Control group (1921 kcal · day-1). There was no significant difference in basal metabolic rate between the groups. PAEE and ExEE were significantly higher in the Exercise group than in the Control group (p<0.01). Habitual exercise induced an increase in TEE without resulting in a compensatory reduction of NExEE. The percentage body fat (fat%) was significantly lower in the Exercise group (25.5%) than in the Control group (30.9%). VO2max was higher in the Exercise group (1788 ml · min-1) than in the Control group (1417 ml. min-1). After correction for body weight, fat% was negatively associated with TEE (p<0.01), PAEE (p<0.01) and ExEE (p=0.05), while VO2max was positively associated with TEE (p<0.05), PAL (p<0.05), PAEE (p<0.05) and ExEE (p<0.01). These results suggest that habitual exercise is associated with the increase of TEE, the improvement of body composition and VO2max. The improvement of VO2max was mainly caused by the increase in ExEE, indicating that the exercise intensity is important to the improvement of cardiorespiratory endurance fitness.

Relation between physical activity and energy expenditure in a representative sample of young children

Strategies for the prevention and treatment of childhood obesity require a better understanding of the relation between the pattern of free-living physical activity and total energy expenditure (TEE). We assessed the relations between TEE and physical activity level (PAL) during engagement in different intensities of physical activity. We used a cross-sectional study of 104 children (median age: 5.4 y) in Scotland. TEE was measured with use of doubly labeled water (DLW), and resting energy expenditure was predicted to determine PAL. Time spent sedentary and in light-intensity activity and in moderate- and vigorous-intensity physical activity (MVPA) was assessed by accelerometry concurrent with DLW measurements. Correlation and regression were used to assess the relations between measures of sedentary behavior, intensities of activity, and PAL as the dependent variable. Time spent sedentary was negatively correlated with PAL (r = -0.33, P < 0.01), and time spent in light-intensity activity was positively correlated with PAL (r = 0.31, P < 0.01). In multiple regression analyses, both time spent sedentary and in light-intensity activities were significantly associated with PAL. Time spent in MVPA was not associated with PAL; engagement in MVPA was limited in this sample (median: 3% of waking hours; range: 0-14%). PAL was significantly higher in boys than in girls. In this sample and setting, PAL was not influenced by engagement in MVPA but was influenced by time spent sedentary and in light-intensity activities. This study suggests that in young children, MVPA could make only a minor contribution to free-living TEE and PAL.

High daily energy expenditure of incubating shorebirds on High Arctic tundra: a circumpolar study

Summary Given the allometric scaling of thermoregulatory capacity in birds, and the cold and exposed Arctic environment, it was predicted that Arctic‐breeding shorebirds should incur high costs during incubation. Using doubly labelled water (DLW), daily energy expenditure (DEE) during incubation was measured in eight shorebird species weighing between 29 and 142 g at various sites in the Eurasian and Canadian High Arctic. The results are compared with a compilation of similar data for birds at lower latitudes. There was a significant positive correlation between species average DEE and body mass (DEE (kJ day−1) = 28·12 BM (g)0·524, r2 = 0·90). The slopes of the allometric regression lines for DEE on body mass of tundra‐breeding birds and lower latitude species (a sample mostly of passerines but including several shorebirds) are similar (0·548 vs 0·545). DEE is about 50% higher in birds on the tundra than in temperate breeding areas. Data for radiomarked Red Knots for which the time budgets during DLW measurements were known, indicated that foraging away from the nest on open tundra is almost twice as costly as incubating a four‐egg clutch. During the incubation phase in the High Arctic, tundra‐breeding shorebirds appear to incur among the highest DEE levels of any time of the year. The rates of energy expenditure measured here are among the highest reported in the literature so far, reaching inferred ceilings of sustainable energy turnover rates.