The effect of feeding on CO2 production and energy expenditure in ponies measured by indirect calorimetry and the 13C-bicarbonate technique

Energy expenditure (EE) can be estimated based on respiratory gas exchange measurements, traditionally done in respiration chambers by indirect calorimetry (IC). However, the ¹³C-bicarbonate technique (¹³C-BT) might be an alternative minimal invasive method for estimation of CO₂ production and EE in the field. In this study, four Shetland ponies were used to explore the effect of feeding on CO₂ production and EE measured simultaneously by IC and ¹³C-BT. The ponies were individually housed in respiration chambers and received either a single oral or intravenous (IV) bolus dose of ¹³C-labelled sodium bicarbonate (NaH¹³CO₃). The ponies were fed haylage 3 h before (T₋₃), simultaneously with (T₀) or 3 h after (T₊₃) administration of ¹³C-bicarbonate. The CO₂ produced and O₂ consumed by the ponies were measured for 6 h with both administration routes of ¹³C-bicarbonate at the three different feeding times. Feeding time affected the CO₂ production (P<0.001) and O₂ consumption (P<0.001), but not the respiratory quotient (RQ) measured by IC. The recovery factor (RF) of ¹³C in breath CO₂ was affected by feeding time (P<0.01) and three different RF were used in the calculation of CO₂ production measured by ¹³C-BT. An average RQ was used for the calculations of EE. There was no difference between IC and ¹³C-BT for estimation of CO₂ production. An effect of feeding time (P<0.001) on the estimated EE was found, with higher EE when feed was offered (T₀ and T₊₃) compared with when no feed was available (T₋₃) during measurements. In conclusion, this study showed that feeding time affects the RF and measurements of CO₂ production and EE. This should be considered when the ¹³C-BT is used in the field. IV administration of ¹³C-bicarbonate is recommended in future studies with horses to avoid complex ¹³C enrichment-time curves with maxima and shoulders as observed in several experiments with oral administration of ¹³C-bicarbonate.     

Effect of feeding time on postprandial nitrogen excretion and energy expenditure in rainbow trout

The effect of feeding time (dawn or midnight) on nitrogen excretion and energy expenditure was studied in immature rainbow trout using measurements of respiratory gas exchange. Fish (mean individual weight 70 g) were maintained indoors under natural photoperiod and fed by hand (commercial food pellets) at a rate of 1% weight/day⁻¹. Rates of ammonia and CO₂ excretion and O₂ uptake were measured every hour. Ammonia excretion increased immediately after feeding in fish fed at midnight, and 2h after feeding in fish fed at dawn. Ammonia excretion and energy supply from protein catabolism, were higher in trout fed at midnight than in those fed at dawn, while total energy expenditure was the same in both groups. The results suggested that trout fed in phase with their natural feeding rhythm use dietary protein more efficiently for growth than do trout fed out of phase with the natural rhythm.     

Evaluation of a multisensor armband in estimating energy expenditure in obese individuals

Objective: To examine the reliability and validity of the SenseWear Pro 2 Armband (SWA; Body Media, Pittsburgh, PA) during rest and exercise compared with indirect calorimetry (IC) in obese individuals. Research Methods and Procedures: Energy expenditure was assessed during rest with the SWA and IC in 142 obese adults (37 men and 105 women, BMI = 42.3 ± 7.0) and in 25 lean and overweight adults (BMI = 25.3 ± 3.2) who were used as a comparison group. Twenty‐nine of the obese adults also participated in three separate short exercise sessions including cycle ergometry, stair stepping, and treadmill walking. Results: The repeatability of SWA estimates in obese subjects was high (r = 0.88, p < 0.001). The SWA generally underestimated the resting energy expenditure (REE) (1811 ± 346 vs. 1880 ± 382 kcal/d) and highly overestimated the energy expenditure during the exercise sessions in obese individuals. REE estimations by SWA were significantly correlated with fat‐free mass (r = 0.88, p < 0.001). Bland‐Altman plots based statistical analysis for the estimated REE, and measured IC showed a low agreement (Total Error > 20% but Systematic Error < 5%) between the two methods in obese subjects, although they showed a high correlation and a very good agreement in lean and overweight patients. Discussion: The SWA is an easy to handle, practical, new portable device for measuring energy expenditure. The accuracy of the SWA appeared to be poor in the obese subjects we examined, especially those with high REE both in rest and exercise. We believe that it is necessary to incorporate new, obesity‐specific algorithms in the relative software.     

Partitioning of late gestation energy expenditure in ewes using indirect calorimetry and a linear regression approach

Abstract

Late gestation energy expenditure (EE_gest) originates from energy expenditure (EE) of development of conceptus (EE_conceptus) and EE of homeorhetic adaptation of metabolism (EE_homeorhetic). Even though EE_gest is relatively easy to quantify, its partitioning is problematic. In the present study metabolizable energy (ME) intake ranges for twin-bearing ewes were 220 – 440, 350 – 700, 350 – 900 kJ per metabolic body weight (W^0.75) at week seven, five, two pre-partum respectively. Indirect calorimetry and a linear regression approach were used to quantify EE_gest and then partition to EE_conceptus and EE_homeorhetic. Energy expenditure of basal metabolism of the non-gravid tissues (EE_bmng), derived from the intercept of the linear regression equation of retained energy [kJ/W^0.75] and ME intake [kJ/W^0.75], was 298 [kJ/W^0.75]. Values of the intercepts of the regression equations at week seven, five, and two pre-partum were 311, 398, and 451 [kJ/W^0.75], respectively. The difference between the intercepts for different weeks was used to calculate EE_homeorhetic. The remaining part of EE_gest was considered to be EE_conceptus. In conclusion, the good agreement between our values of EE_conceptus and those in the literature indicates the method's validity.     

Physical Activity in Confined Conditions as an Indicator of Free‐Living Physical Activity

Objective: The main determinants of daily energy expenditure are body size and physical activity. Activity energy expenditure is the most variable component of total energy expenditure. It was assessed whether the physical activity level in confined conditions is an indicator of free‐living physical activity. Research Methods and Procedures: Activity energy expenditure was measured over 1 day in a confined environment of a respiration chamber (floor space, 7.0 m²), where activities were restricted to low‐intensity activities of daily living, and over 2 weeks in a free‐living environment using doubly labeled water. Subjects were 16 women and 29 men (age, 31 ± 10 years; BMI, 24.2 ± 2.7 kg/m²). Results: The free‐living activity level of the subjects, as a multiple of resting energy expenditure, was 1.76 ± 0.13. Activity energy expenditure in the chamber was 47 ± 13% of the value in daily life, and the two values were correlated (r = 0.50, p < 0.001; partial correlation corrected for age, gender, and BMI: 0.40, p < 0.01). The chamber value explained 25% of the total variance in free‐living activity energy expenditure. Discussion: The activity level of a subject under sedentary conditions is an indicator of activity energy expenditure in daily life, showing the importance of nonexercise activity for daily energy expenditure.     

人体能量消耗构成比数学模型

为了评价人体能量消耗构成比,本文描述了构建人体能量消耗的三大营养素构成比数学模型的推演过程。总氧消耗、总二氧化碳排出和总氮（尿氮＋皮肤氮）排出与三大营养素的氧化有关,并且这三种营养素的生理燃烧值是已知的。基于这些可测定的和已知的参数,我们构建的数学模型有助于了解受试个体的能量消耗特点。     

Physical activity compliance: differences between overweight/obese and normal-weight adults

Objectives: Comparisons of physical activity measured by accelerometers in overweight/obese adults and their normal‐weight counterparts are limited. Compliance with the 2002 Institute of Medicine (IOM) exercise recommendations for 60 minutes of moderate‐intensity exercise daily has not been reported. The purpose of this study was to compare physical activity, as measured by accelerometers, in overweight/obese adults vs. normal‐weight controls and to assess compliance with recommendations for physical activity by the IOM in 2002 and by the Centers for Disease Control and Prevention and American College of Sports Medicine in 1995 for 30 minutes of moderate‐intensity activity, preferably all days of the week. Research Methods and Procedures: Sixty‐two overweight/obese subjects, BMI ≥ 25, included 31 adults, 12 men and 19 women, 25 to 69 years old, and their normal‐weight controls, BMI 18.5 to 24.9, matched for gender, age, and height. Body composition was assessed using DXA. Physical activity was measured with Actigraph accelerometers (MTI, Fort Walton Beach, FL) worn by each participant for 7 consecutive days. Results: Accelerometry data indicated that overweight/obese adults recorded ～60 counts per minute less per day and spent 21 minutes less engaged in moderate or greater intensity activity than their normal‐weight counterparts. Although 71% to 94% of those studied met 1995 recommendations, only 13% of overweight/obese subjects and 26% of normal‐weight participants met 2002 exercise recommendations. Discussion: These results suggest that daily minutes spent in moderate‐intensity activity or greater are associated with weight status and that the 2002 IOM recommendations may be difficult to meet even for normal‐weight individuals.     

Physical activity assessment with accelerometers: an evaluation against doubly labeled water

This review focuses on the ability of different accelerometers to assess daily physical activity as compared with the doubly labeled water (DLW) technique, which is considered the gold standard for measuring energy expenditure under free-living conditions. The PubMed Central database (U.S. NIH free digital archive of biomedical and life sciences journal literature) was searched using the following key words: doubly or double labeled or labeled water in combination with accelerometer, accelerometry, motion sensor, or activity monitor. In total, 41 articles were identified, and screening the articles' references resulted in one extra article. Of these, 28 contained sufficient and new data. Eight different accelerometers were identified: 3 uniaxial (the Lifecorder, the Caltrac, and the CSA/MTI/Actigraph), one biaxial (the Actiwatch AW16), 2 triaxial (the Tritrac-R3D and the Tracmor), one device based on two position sensors and two motion sensors (ActiReg), and the foot-ground contact pedometer. Many studies showed poor results. Only a few mentioned partial correlations for accelerometer counts or the increase in R(2) caused by the accelerometer. The correlation between the two methods was often driven by subject characteristics such as body weight. In addition, standard errors or limits of agreement were often large or not presented. The CSA/MTI/Actigraph and the Tracmor were the two most extensively validated accelerometers. The best results were found for the Tracmor; however, this accelerometer is not yet commercially available. Of those commercially available, only the CSA/MTI/Actigraph has been proven to correlate reasonably with DLW-derived energy expenditure.     

Triaxial accelerometry for assessment of physical activity in young children

Objective: The purpose of the present study was to derive linear and non‐linear regression equations that estimate energy expenditure (EE) from triaxial accelerometer counts that can be used to quantitate activity in young children. We are unaware of any data regarding the validity of triaxial accelerometry for assessment of physical activity intensity in this age group. Research Methods and Procedures: EE for 27 girls and boys (6.0 ± 0.3 years) was assessed for nine activities (lying down, watching a video while sitting and standing, line drawing for coloring‐in, playing blocks, walking, stair climbing, ball toss, and running) using indirect calorimetry and was then estimated using a triaxial accelerometer (ActivTracer, GMS). Results: Significant correlations were observed between synthetic (synthesized tri‐axes as the vector), vertical, and horizontal accelerometer counts and EE for all activities (0.878 to 0.932 for EE). However, linear and non‐linear regression equations underestimated EE by >30% for stair climbing (up and down) and performing a ball toss. Therefore, linear and non‐linear regression equations were calculated for all activities except these two activities, and then evaluated for all activities. Linear and non‐linear regression equations using combined vertical and horizontal acceleration counts, synthetic counts, and horizontal counts demonstrated a better relationship between accelerometer counts and EE than did regression equations using vertical acceleration counts. Adjustment of the predicted value by the regression equations using the vertical/horizontal counts ratio improved the overestimation of EE for performing a ball toss. Discussion: The results suggest that triaxial accelerometry is a good tool for assessing daily EE in young children.     

Late isocaloric eating increases hunger,decreases energy expenditure,and modifies metabolic pathways in adults with overweight and obesity

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Combination of meal and exercise timing with a high-fat diet influences energy expenditure and obesity in mice

In mice, obesity has been observed not only in those freely fed a high-fat diet (HFD) but also in those fed while physically inactive. In contrast, a HFD during physically active periods protects against obesity and the impairments in the circadian rhythm induced by free feeding of a HFD. Although exercise is known to be effective for obesity prevention and management, the optimal timing of exercise has not yet been determined. In the present experiments, we aimed to determine the best combination of daily timing of HFD consumption and exercise for the prevention of HFD-induced weight gain in mice. In this experiment, “morning” refers to the beginning of the active phase (the “morning” for nocturnal animals). Increases in body weight related to free feeding of a HFD was significantly reduced with 4?h of exercise during the late (evening) or middle (noon) active period compared to 4?h of exercise during the early (morning) active period or free access to exercise, which resulted in hours of exercise similar to that of morning exercise. These results suggested that eating in the morning or at noon followed by exercise in the evening could prevent weight gain more effectively than exercise in the morning followed by eating at noon or in the evening. The group fed a HFD for 4?h in the morning had lower body weight than the group fed a HFD for 4?h in the evening without exercise. The last group of experiments tested the hypothesis that there would be an interaction between mealtime and exercise time (i.e. time of day) versus order (i.e. which comes first) effects. We compared groups that exercised for 4?h at noon and were fed either in the morning or evening and groups that were fed for 4?h at noon and either exercised in the morning or evening. We found that the groups that were fed before exercise gained less body and fat weight and more skeletal muscle weight compared to the groups that exercised before eating. Corresponding to the body and fat weight changes, the respiratory exchange ratio (RER) was lower and energy expenditure was higher in the groups fed before exercise than in the groups fed after exercise, and these effects on energy metabolism were also observed in the early stage of HFD feeding before obesity. When obese mice fed a HFD for 12 weeks were exposed to a combination of feeding and exercise timing in an effort to reduce body weight, eating followed by exercise resulted in greater weight loss, similar to the experiments conducted to prevent weight gain. These results demonstrate that a combination of daily timing of eating and exercise may influence weight gain and that eating followed by exercise may be effective for minimizing increases in body and fat weight as well as maximizing increases in skeletal muscle weight.     

Comparisons of energy intake and energy expenditure in overweight and obese women with and without binge eating disorder

The purpose of this study was to determine whether there are differences in energy intake or energy expenditure that distinguish overweight/obese women with and without binge eating disorder (BED). Seventeen overweight/obese women with BED and 17 overweight/obese controls completed random 24-h dietary recall interviews, and had total daily energy expenditure (TDEE) assessed by the doubly labeled water (DLW) technique with concurrent food log data collection. Participants received two baseline dual-energy X-ray absorptiometry (DXA) scans and had basal metabolic rate (BMR) and thermic effect of food (TEF) measured using indirect calorimetry. Results indicated no between group differences in TDEE, BMR, and TEF. As in our previous work, according to dietary recall data, the BED group had significantly higher caloric intake on days when they had binge eating episodes than on days when they did not (3,255 vs. 2,343 kcal). There was no difference between BED nonbinge day intake and control group intake (2,233 vs. 2,140 kcal). Similar results were found for food log data. Dietary recall data indicated a trend toward higher average daily intake in the BED group (2,587 vs. 2,140 kcal). Furthermore, when comparing TDEE to dietary recall and food log data, both groups displayed significant under-reporting of caloric intake of similar magnitudes ranging from 20 to 33%. Predicted energy requirements estimated via the Harris-Benedict equation (HBE) underestimated measured TDEE by 23-24%. Our data suggest that increased energy intake reported by BED individuals is due to increased food consumption and not metabolic or under-reporting differences.     

Assessment of Free‐Living Physical Activity in Humans: An Overview of Currently Available and Proposed New Measures

The number of physical activity measures and indexes used in the human literature is large and may result in some difficulty for the average investigator to choose the most appropriate measure. Accordingly, this review is intended to provide information on the utility and limitations of the various measures. Its primary focus is the objective assessment of free‐living physical activity in humans based on physiological and biomechanical methods. The physical activity measures have been classified into three categories:

• 1 . Measures based on energy expenditure or oxygen uptake, such as activity energy expenditure, activity‐related time equivalent, physical activity level, physical activity ratio, metabolic equivalent, and a new index of potential interest, daytime physical activity level.
• 2 . Measures based on heart rate monitoring, such as net heart rate, physical activity ratio heart rate, physical activity level heart rate, activity‐related time equivalent, and daytime physical activity level heart rate.
• 3 . Measures based on whole‐body accelerometry (counts/U time).

Quantification of the velocity and duration of displacement in outdoor conditions by satellites using the Differential Global Positioning System may constitute a surrogate for physical activity, because walking is the primary activity of man in free‐living conditions. A general outline of the measures and indexes described above is presented in tabular form, along with their respective definition, usual applications, advantages, and shortcomings. A practical example is given with typical values in obese and non‐obese subjects. The various factors to be considered in the selection of physical activity methods include experimental goals, sample size, budget, cultural and social/environmental factors, physical burden for the subject, and statistical factors, such as accuracy and precision. It is concluded that no single current technique is able to quantify all aspects of physical activity under free‐living conditions, requiring the use of complementary methods. In the future, physical activity sensors, which are of low‐cost, small‐sized, and convenient for subjects, investigators, and clinicians, are needed to reliably monitor, during extended periods in free‐living situations, small changes in movements and grade as well as duration and intensity of typical physical activities.     

Antioxidant supplementation lowers exercise-induced oxidative stress in young overweight adults

Objective: To determine whether antioxidant (AOX) supplementation attenuates post‐exercise oxidative stress and contributors to oxidative stress (inflammation, blood lipids) in overweight young adults. Research Methods and Procedures: This was a randomized, double‐blind, controlled study. Overweight (BMI, 33.2 ± 1.9 kg/m²) and comparative normal‐weight (BMI, 21.9 ± 0.5 kg/m²) adults 18 to 30 years old (total N = 48) were enrolled. Participants received either daily antioxidant (AOX) treatment (800 IU of vitamin E, 500 mg of vitamin C, 10 mg of β‐carotene) or placebo (PL) for 8 weeks for a total of four groups. All participants completed a standardized 30‐minute cycle exercise bout at baseline and 8 weeks. Exercise‐induced changes in lipid hydroperoxide (ΔPEROX), C‐reactive protein (ΔCRP), interleukin‐6 (ΔIL‐6), cholesterol subfractions, triglycerides, total AOX status (ΔTAS), and adiponectin were assessed. Results: Exercise‐induced ΔPEROX was lower in the overweight‐AOX group (0.09 nM/kg per min) compared with PL‐treated overweight and normal‐weight groups (0.98, 0.53 nM/kg per min) by 8 weeks (p < 0.05). Adiponectin was increased in both overweight and normal‐weight AOX groups (22.1% vs. 3.1%; p < 0.05) but reduced in PL groups. ΔIL‐6, Δtotal cholesterol, and Δlow‐density lipoprotein‐cholesterol concentrations during exercise were lower in the AOX‐treated groups compared with PL groups (all p < 0.05). After controlling for BMI, the Δtotal cholesterol, Δlow‐density lipoprotein‐cholesterol, Δadiponectin, and ΔTAS explained 59.1% of the variance of the regression model of the ΔPEROX by 8 weeks (total model R² = 0.600; p = 0.015). Discussion: AOX lowers exercise‐induced oxidative stress in overweight adults. Inflammatory and lipid markers may also be attenuated with AOX. Further studies are needed to determine whether AOX may be used in cardiovascular disease prevention in the overweight population.     

Weekend and weekday patterns of physical activity in overweight and normal-weight adolescent girls

Objective: To describe the patterns (specifically comparing weekdays and weekends classified by intensities) of physical activity (PA) measured by accelerometry in adolescent girls. Research Methods and Procedures: Healthy sixth grade girls (n = 1603), 11 to 12 years old, were randomly recruited from 36 schools participating in the Trial of Activity in Adolescent Girls. Age, ethnicity, socioeconomic status, weight, and height were taken. PA patterns were measured for 6 days using accelerometry. Results: Adolescent girls spend most of their time in sedentary (52% to 57% of the day) and light activity (40% to 45% of the day) on weekdays and weekends. In all girls, total PA comprised 44.5% of the day (41.7% light, 2.2% moderate, and 0.7% vigorous) with sedentary activity comprising 55.4%. Moderate‐to‐vigorous PA (MVPA) was higher (p < 0.001) on weekdays than weekends in all girls, but MVPA was lower in at‐risk of overweight + overweight girls (p < 0.001) on both weekdays and weekends compared with normal‐weight girls. Discussion: Adolescent girls are more active at moderate and vigorous intensities on weekdays than on weekends, and at‐risk of overweight and those overweight spend less time engaging in MVPA than normal‐weight girls.     

Resistance training lowers exercise-induced oxidative stress and homocysteine levels in overweight and obese older adults

Objective: To compare exercise‐induced oxidative stress and levels of homocysteine and cholesterol in normal‐weight and overweight older adults after resistance exercise (RX). Research Methods and Procedures: This interventional study was conducted at a wellness center. Forty‐nine older adults (age range, 60 to 72 years) were stratified by BMI (<25 kg/m² normal weight, ≥25 kg/m² overweight/obese) and then randomly assigned to either a control non‐exercise group or an RX group. The RX group completed a 6‐month training program. Exercise‐induced lipid hydroperoxides (PEROXs) and thiobarbituric‐reactive acid substances, homocysteine, lipoprotein a, cholesterol, and high‐density lipoprotein cholesterol were measured before and after the 6‐month RX program. Results: PEROXs and thiobarbituric‐reactive acid substances were lower in both the overweight/obese and normal‐weight RX‐trained groups compared with control groups (p < 0.05). Homocysteine levels were lower in both overweight/obese and normal‐weight RX groups compared with control groups (p < 0.05). Lipoprotein a, total cholesterol, and high‐density lipoprotein cholesterol were not different in normal‐weight and overweight/obese groups before or after RX. The change in muscle strength was correlated with homocysteine at 6 months (r = ?0.452, p < 0.05), whereas the change in PEROXs was correlated with the change in body fat (r = ?0.329). Discussion: To our knowledge, these data are the first to show that RX reduces exercise‐induced oxidative stress and homocysteine regardless of adiposity, indicating that this protection can be afforded in an older, overweight/obese population as effectively as in healthy older adults. These data suggest that RX may afford some protection against emerging cardiovascular risk factors using a mode of exercise that supports body weight.     

Implementation of field cardio-respiratory measurements to assess energy expenditure in Arabian endurance horses

Measurements of respiratory exchanges in genuine exercise conditions are undoubtedly of interest to further define the energy needs of endurance horses. However, the equine K4b², the gas exchanges portable device validated for equines, has not been used in Arabian endurance horses yet. Therefore, the objective of this study was to implement field cardio-respiratory measurements in such horses using the equine K4b² in order to assess energy expenditure (EE). Measurements of heart rate (HR), oxygen uptake (VO₂), carbon dioxide production (VCO₂), respiratory frequency (RF), tidal volume (VT) and minute expired volume (VE) were carried out at rest and during a 20-min submaximal incremental field exercise in five trained Arabian endurance horses equipped with the K4b² system. The relationship between HR and VO₂ was determined for each horse. EE of the exercise session was calculated from direct VO₂ measurements and individual HR-VO₂ regression. Out of the five horses, four tolerated the equipment. Respiratory and metabolic variables at rest and during exercise, as well as EE measured at the different gaits, were consistent with reported values in exercising horses: VO₂ ranged from 4.8 to 54.1 ml/min per kg from rest to canter, respectively, and EE from 82 to 1095 J/min per kg BW. The 20-min exercise session EE accounted for 6258 and 6332 J from direct VO₂ measurements and individual HR-VO₂ regression, respectively, which did not differ significantly. Providing an adaptation period and several technical adjustments, the present equine K4b² could be used to assess EE in Arabian endurance horses in a controlled environment. The prediction of EE from the individual VO₂–HR relationship might be an alternative method to evaluate EE when VO₂ measurements are not possible.     

Physical activity and energy expenditure in lean and obese adult human subjects.

We compared the physical activity of 11 lean and 11 obese men and women over a 7-day period. There were no significant differences in either the amount of movement recorded with an accelerometer (9.5 (SD 3.9) vs 9.9 (SD 2.6) kcounts.day-1), or in the energy expenditure due to physical activity reflected by the difference between the average daily metabolic rate measured by the doubly labelled water technique and the sleeping metabolic rate measured in a respiration chamber and adjusted for fat-free mass: 112 (SD 33) vs 118 (SD 22) kJ.kg-1.day-1. The obese showed a non-significant loss of body mass of 0.5 (SD 1.1) kg, probably due to reduced intake during the 7-day intake recording period.     

Body size and human energy requirements: reduced mass-specific resting energy expenditure in tall adults.

Two observations favor the presence of a lower mass-specific resting energy expenditure (REE/weight) in taller adult humans: an earlier report of height (H)-related differences in relative body composition; and a combined model based on Quetelet and Kleiber's classic equations suggesting that REE/weight proportional, variantH(-0.5). This study tested the hypothesis stating that mass-specific REE scales negatively to height with a secondary aim exploration of related associations between height, weight (W), surface area (SA), and REE. Two independent data sets (n = 344 and 884) were evaluated, both with REE measured by indirect calorimetry and the smaller of the two including fat estimates by dual-energy X-ray absorptiometry. Results support Quetelet's equation (W proportional, variantH(2)), but Kleiber's equation approached the interspecific mammal form (REE proportional, variantW(0.75)) only after adding adiposity measures to weight and age as REE predictors. REE/weight scaled as H( approximately (-0.5)) in support of the hypothesis with P values ranging from 0.17 to <0.001. REE and SA both scaled as H( approximately 1.5), and REE/SA was nonsignificantly correlated with height in all groups. These observations suggest that adiposity needs to be considered when evaluating the intraspecific scaling of REE to weight; that relative to their weight, taller subjects require a lower energy intake for replacing resting heat losses than shorter subjects; that fasting endurance, approximated as fat mass/REE, increases as H(0.5); and that thermal balance is maintained independent of stature by evident stable associations between resting heat production and capacity of external heat release. These observations have implications for the modeling of adult human energy requirements and associate with anthropological concepts founded on body size.