Energy expenditure by doubly labeled water: validation in lean and obese subjects

First use of triply labelled water analysis for energy expenditure measurements in mice

The doubly labelled water (DLW) method is widely used to determine energy expenditure. In this work, we demonstrate the addition of the third stable isotope, ¹⁷O, to turn it into triply labelled water (TLW), using the three isotopes measurement of optical spectrometry. We performed TLW (²H, ¹⁸O and¹⁷O) measurements for the analysis of the CO₂ production (r_CO2) of mice on different diets for the first time. Triply highly enriched water was injected into mice, and the isotope enrichments of the distilled blood samples of one initial and two finals were measured by an off-axis integrated cavity output spectroscopy instrument. We evaluated the impact of different calculation protocols and the values of evaporative water loss fraction. We found that the dilution space and turnover rates of ¹⁷O and ¹⁸O were equal for the same mice group, and that values of r_CO2 calculated based on ¹⁸O–²H, or on ¹⁷O–²H agreed very well. This increases the reliability and redundancy of the measurements and it lowers the uncertainty in the calculated r_CO2 to 3% when taking the average of two DLW methods. However, the TLW method overestimated the r_CO2 compared to the indirect calorimetry measurements that we also performed, much more for the mice on a high-fat diet than for low-fat. We hypothesize an extra loss or exchange mechanism with a high fractionation for ²H to explain this difference.

Nutrient Density as a Dimension of Dietary Quality: Findings of the Nutrient Density Approach in a Multi-Center Evaluation

The nutrient adequacy of a diet is typically assessed by comparing estimated nutrient intakes with established average nutrient requirements; this approach does not consider total energy consumed. In this multinational survey investigation in Indonesia, Mexico, and South Africa, we explore the applications of the “critical nutrient-density approach”—which brings energy requirements into the equation—in the context of public health epidemiology. We conducted 24 h dietary recalls in convenience samples of normal-weight (BMI 18.5–25 kg/m²) or obese (BMI > 30 kg/m²), low-income women in three settings (n = 290). Dietary adequacy was assessed both in absolute terms and using the nutrient density approach. No significant differences in energy and nutrient intakes were observed between normal-weight and obese women within any of the three samples (p > 0.05). Both the cut-point method (% of EAR) and critical nutrient density approach revealed a high probability of inadequate intakes for several micronutrients but with poor concordance between the two methods. We conclude that it may often require some approximate estimate of the habitual energy intake from an empirical source to apply a true critical nutrient density reference for a population or subgroup. This will logically signify that there would be more “problem nutrients” in the diets examined with this nutrient density approach, and efforts toward improved food selection or food- or biofortification will frequently be indicated.

Changes in body weight and metabolic risk during time restricted feeding in premenopausal versus postmenopausal women

BACKGROUND

Time restricted feeding (TRF) involves confining the eating window to a specific number of hours, and fasting for the remaining hours of the day.

OBJECTIVE

This study examined if changes in body weight and metabolic risk factors during TRF, differ between premenopausal and postmenopausal women.

METHODS

This is a secondary analysis of an 8-week TRF study (4-6 h eating window, 18-20 h fasting window daily) conducted in adults with obesity. Male participants were excluded, and female subjects were classified in two groups based on menstrual status: premenopausal (n = 13), or postmenopausal (n = 19). Perimenopausal women were excluded from the original study.

RESULTS

Body weight decreased by week 8 in premenopausal women (-3.3 ± 0.4%) and postmenopausal women (-3.3 ± 0.5%) (main effect of time, P < 0.001), with no difference between groups (no group × time interaction). Adherence was excellent in both groups, with premenopausal women adhering to their prescribed eating window on 6.2 ± 0.1 d/week, and postmenopausal women adhering to their window on 6.2 ± 0.2 d/week. Fat mass, lean mass, fasting insulin, insulin resistance, and 8-isoprostane (marker of oxidative stress) were reduced similarly in both groups (main effect of time, P < 0.05 for all comparisons). Visceral fat mass, relative skeletal muscle index (RSMI), blood pressure, LDL cholesterol, HDL cholesterol, triglycerides, fasting glucose, HbA1c, TNF-alpha and IL-6 remained unchanged in both groups by week 8.

CONCLUSION

These findings suggest that the weight loss and metabolic benefits of TRF do not differ between premenopausal and postmenopausal women with obesity.

A standard calculation methodology for human doubly labeled water studies

The doubly labeled water (DLW) method measures total energy expenditure (TEE) in free-living subjects. Several equations are used to convert isotopic data into TEE. Using the International Atomic Energy Agency (IAEA) DLW database (5,756 measurements of adults and children), we show considerable variability is introduced by different equations. The estimated rCO₂ is sensitive to the dilution space ratio (DSR) of the two isotopes. Based on performance in validation studies, we propose a new equation based on a new estimate of the mean DSR. The DSR is lower at low body masses (<10 kg). Using data for 1,021 babies and infants, we show that the DSR varies non-linearly with body mass between 0 and 10 kg. Using this relationship to predict DSR from weight provides an equation for rCO₂ over this size range that agrees well with indirect calorimetry (average difference 0.64%; SD = 12.2%). We propose adoption of these equations in future studies.

Effect of fasting on body composition and proteolysis gene expression in skeletal muscles and liver of BEH+/+ and BEL mice

Fasting improves health, but can cause muscle weakness. We assessed body composition in 21-week old males of Berlin high (BEH+/+) and Berlin low (BEL) strains after two bouts of 48-h or 40-h of fasting with 5-day refeeding in between, respectively. BEH+/+ mice tended to loose less weight than BEL in bout 1 and 2 (16.0 ± 2.7 versus 23.5 ± 2.9%, p < 0.001 and 17.1 ± 3.4 versus 20.4 ± 3.4%, p = 0.17, respectively). In spite of greater serum IGF-1 and body fat levels, BEH+/+ mice showed more severe muscle atrophy, but less marked liver wasting and fat depletion than BEL mice. BEH+/+ mice also showed smaller increases in expression of p62, Atrogin-1, and Mstn genes in skeletal muscles. In summary, BEL mice show resistance to fasting-induced muscle wasting in spite of low serum IGF-1 levels and high expression of genes associated with muscle atrophy.

Validity of Accelerometers for the Evaluation of Energy Expenditure in Obese and Overweight Individuals: A Systematic Review

OBJECTIVE

Even though the validity of accelerometers for the measurement of energy expenditure (EE) has been demonstrated for normal-weight individuals, the applicability of this instrument in obese individuals remains controversial. This review aims to summarize the level of agreement between accelerometers and the gold standards (indirect calorimetry and doubly labelled water) for the measurement of energy expenditure (EE) in obese or overweight individuals.

METHODS

The literature search was limited to comparison studies assessing agreement in EE determination between accelerometers and indirect calorimetry (IC) or doubly labelled water (DLW). We searched in PubMed and in Scopus until March 1, 2019. The analysis was restricted to obese or overweight adult individuals. The following descriptive information was extracted for each study: sample size, characteristics of participants (sex, age, BMI, fat mass percentage, any pathological conditions, modality of recruitment in the study, and exclusion criteria), accelerometer description (model, type and body position), and type of gold standard and validity protocol (duration, conditions, and requirements during and before the experiment). Three review authors independently screened the obtained results, and the quality of the selected articles was assessed by the QUADAS-2 tool.

RESULTS

We obtained seventeen eligible articles, thirteen of which showed concerns for the applicability section, due to the patient selection. Regarding the accelerometers, nine devices were validated in the included studies with the BodyMedia SenseWear® (SWA) being the most frequently validated. Although correlations between accelerometers and the gold standard were high in some studies, agreement between the two methods was low, as shown by the Bland-Altman plots.

CONCLUSIONS

Most accelerometer estimations of EE were inaccurate for obese/overweight subjects, and authors advise to improve the accuracy of algorithms for SWA software, or the predicted equations for estimating EE from other accelerometers.

Traditional Self-Reported Dietary Instruments Are Prone to Inaccuracies and New Approaches Are Needed

Background: Diet is a modifiable behavior that influences an individual's health. Because of this, diet assessment is an important component of public health surveillance, evaluating response to community health interventions, and monitoring individual compliance to medical interventions. Diet assessments are usually performed using one of three basic methods: diet recall, diet diaries, or food frequency questionnaires. Although these three assessment instruments have displayed a strong agreement between themselves, when reported intake is compared with intake measured using quantitative nutrient biomarkers, investigators have identified systematic misreporting errors for all three of these self-reported dietary instruments.

Aims: This work aims to summarize the state of knowledge regarding misreporting and why it impedes diet–health research and to introduce advances in the collection and the treatment of dietary data.

Methods: This work reviews and summarizes published data on misreporting and the recent efforts to reduce such errors.

Results: The evidence demonstrates a strong and consistent systematic underreporting of energy intake (EIn) across adults and children studies. Underreporting of EIn has been found to increase with body mass index (BMI), and the differences between macronutrient reports indicate that not all foods are underreported equally. Protein is least underreported, but which specific foods are commonly underreported are not known.

Conclusions: Because energy underreporting varies as a function of BMI, self-reported EIn should not be used for the study of energy balance in the study of obesity. The between-individual variability in the underreporting of self-reported intake of energy and other nutrients attenuates diet–disease relationships. Recent efforts to correct for underreporting have reduced misreporting of diet outcomes, but improvements have been incremental in nature and more research is needed to validate and extend these efforts.

A low resting metabolic rate in late childhood is associated with weight gain in adolescence

BACKGROUND AND OBJECTIVES

Lower total energy expenditure (TEE) and resting metabolic rate (RMR) are associated with greater weight gain in Native American adults. Whether these effects exist in childhood is unclear. We hypothesized that lower energy expenditure measured in childhood would predict greater relative change in body mass index (BMI) during adolescence.

METHODS

Measurements of height, weight, body composition, RMR and TEE were completed in 181 Native American children at exams done at age 5 and 10years, with 126 children having biennial follow-up assessments of weight and height after age 10years until age 20years. TEE and RMR were adjusted for age, sex, height, fat mass and fat free mass. BMI-change was assessed using population specific and Center for Disease Control (CDC) BMI z-scores and change in the relative difference to the 95th BMI-centile.

RESULTS

Lower adjusted RMR at age 10years was associated with greater increase in population-specific and CDC BMI z-scores, greater increase in the relative difference to the 95th BMI-centile and greater weight gain (all r≤-0.22, p≤0.01). However, no association was found with adjusted RMR at age 5years and with adjusted TEE and physical activity level assessed at age 5 or 10years.

CONCLUSIONS

Lower adjusted RMR at age 10years predicted greater change in adolescent BMI z-score indicating that the effects of relatively low metabolic rate on future weight gain in this population may begin in late childhood.

Total energy expenditure is comparable between patients with and without diabetes mellitus: Clinical Evaluation of Energy Requirements in Patients with Diabetes Mellitus (CLEVER-DM) Study

OBJECTIVE

Assessment of total energy expenditure (TEE) is essential for appropriate recommendations regarding dietary intake and physical activity in patients with and without diabetes mellitus (DM). However, few reports have focused on TEE in patients with DM, particularly in Asian countries. Therefore, we evaluated TEE in Japanese patients with DM using the doubly labeled water (DLW) method and physical activity level (PAL).

RESEARCH DESIGN AND METHODS

In this cross-sectional observational study, we evaluated 52 patients with type 2 DM and 15 patients without DM. Free-living TEE was measured over 12-16 days by the DLW method, and PAL was calculated as TEE divided by the basal metabolic rate (BMR) as assessed by indirect calorimetry. The equivalence margin was defined as 5 kcal/kg/day.

RESULTS

The numbers of patients with DM treated with insulin, oral antidiabetic drugs, and diet were 18 (34.6%), 20 (38.5%), and 14 (26.9%), respectively. The mean±SD level of glycated hemoglobin was 6.9%±0.8% and 5.5%±0.3% in the DM and non-DM group, respectively (p<0.001). The mean body mass index was 23.3±3.0 and 22.7±2.1 kg/m² in the DM and non-DM group, respectively. The mean TEE per kilogram body weight adjusted for sex and age was 36.5 kcal/kg/day and 37.5 kcal/kg/day in the DM and non-DM group, respectively, with no significant difference (mean difference, -1.0 kcal/kg/day; 95% CI -4.2 to 2.3 kcal/kg/day). The BMR tended to be higher in the DM than in the non-DM group (mean difference, 33 kcal/day; 95% CI, -15 to 80 kcal/day). The mean PAL adjusted for sex and age was 1.71 and 1.81 in the DM and non-DM group, respectively, without a significant difference (mean difference, -0.10; 95% CI -0.21 to 0.01).

CONCLUSION

TEE was comparable between Japanese patients with and without DM.

TRIAL REGISTRATION NUMBER

UMIN000023051.

Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: randomized trial

OBJECTIVE

To determine the effects of diets varying in carbohydrate to fat ratio on total energy expenditure.

DESIGN

Randomized trial.

SETTING

Multicenter collaboration at US two sites, August 2014 to May 2017.

PARTICIPANTS

164 adults aged 18-65 years with a body mass index of 25 or more.

INTERVENTIONS

After 12% (within 2%) weight loss on a run-in diet, participants were randomly assigned to one of three test diets according to carbohydrate content (high, 60%, n=54; moderate, 40%, n=53; or low, 20%, n=57) for 20 weeks. Test diets were controlled for protein and were energy adjusted to maintain weight loss within 2 kg. To test for effect modification predicted by the carbohydrate-insulin model, the sample was divided into thirds of pre-weight loss insulin secretion (insulin concentration 30 minutes after oral glucose).

MAIN OUTCOME MEASURES

The primary outcome was total energy expenditure, measured with doubly labeled water, by intention-to-treat analysis. Per protocol analysis included participants who maintained target weight loss, potentially providing a more precise effect estimate. Secondary outcomes were resting energy expenditure, measures of physical activity, and levels of the metabolic hormones leptin and ghrelin.

RESULTS

Total energy expenditure differed by diet in the intention-to-treat analysis (n=162, P=0.002), with a linear trend of 52 kcal/d (95% confidence interval 23 to 82) for every 10% decrease in the contribution of carbohydrate to total energy intake (1 kcal=4.18 kJ=0.00418 MJ). Change in total energy expenditure was 91 kcal/d (95% confidence interval -29 to 210) greater in participants assigned to the moderate carbohydrate diet and 209 kcal/d (91 to 326) greater in those assigned to the low carbohydrate diet compared with the high carbohydrate diet. In the per protocol analysis (n=120, P<0.001), the respective differences were 131 kcal/d (-6 to 267) and 278 kcal/d (144 to 411). Among participants in the highest third of pre-weight loss insulin secretion, the difference between the low and high carbohydrate diet was 308 kcal/d in the intention-to-treat analysis and 478 kcal/d in the per protocol analysis (P<0.004). Ghrelin was significantly lower in participants assigned to the low carbohydrate diet compared with those assigned to the high carbohydrate diet (both analyses). Leptin was also significantly lower in participants assigned to the low carbohydrate diet (per protocol).

CONCLUSIONS

Consistent with the carbohydrate-insulin model, lowering dietary carbohydrate increased energy expenditure during weight loss maintenance. This metabolic effect may improve the success of obesity treatment, especially among those with high insulin secretion.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02068885.

A randomized study of dietary composition during weight-loss maintenance: Rationale, study design, intervention, and assessment

BACKGROUND

While many people with overweight or obesity can lose weight temporarily, most have difficulty maintaining weight loss over the long term. Studies of dietary composition typically focus on weight loss, rather than weight-loss maintenance, and rely on nutrition education and dietary counseling, rather than controlled feeding protocols. Variation in initial weight loss and insufficient differentiation among treatments confound interpretation of results and compromise conclusions regarding the weight-independent effects of dietary composition. The aim of the present study was to evaluate three test diets differing in carbohydrate-to-fat ratio during weight-loss maintenance.

DESIGN AND DIETARY INTERVENTIONS

Following weight loss corresponding to 12±2% of baseline body weight on a standard run-in diet, 164 participants aged 18 to 65years were randomly assigned to one of three test diets for weight-loss maintenance through 20weeks (test phase). We fed them high-carbohydrate (60% of energy from carbohydrate, 20% fat), moderate-carbohydrate (40% carbohydrate, 40% fat), and low-carbohydrate (20% carbohydrate, 60% fat) diets, controlled for protein content (20% of energy). During a 2-week ad libitum feeding phase following the test phase, we assessed the effect of the test diets on body weight.

OUTCOMES

The primary outcome was total energy expenditure, assessed by doubly-labeled water methodology. Secondary outcomes included resting energy expenditure and physical activity, chronic disease risk factors, and variables to inform an understanding of physiological mechanisms by which dietary carbohydrate-to-fat ratio might influence metabolism. Weight change during the ad libitum feeding phase was conceptualized as a proxy measure of hunger.

Validity of the Remote Food Photography Method Against Doubly Labeled Water Among Minority Preschoolers

OBJECTIVE

The aim of this study was to determine the validity of energy intake (EI) estimations made using the remote food photography method (RFPM) compared to the doubly labeled water (DLW) method in minority preschool children in a free-living environment.

METHODS

Seven days of food intake and spot urine samples excluding first void collections for DLW analysis were obtained on thirty-nine 3- to 5-year-old Hispanic and African American children. Using an iPhone, caregivers captured before and after pictures of each child's intake, pictures were wirelessly transmitted to trained raters who estimated portion size using existing visual estimation procedures, and energy and macronutrients were calculated. Paired t tests, mean differences, and Bland-Altman limits of agreement were performed.

RESULTS

The mean EI was 1,191 ± 256 kcal/d using the RFPM and 1,412 ± 220 kcal/d using the DLW method, resulting in a mean underestimate of 222 kcal/d (-15.6%; P < 0.0001) that was consistent regardless of intake. The RFPM underestimated EI by -28.5% in 34 children and overestimated EI by 15.6% in 5 children.

CONCLUSIONS

The RFPM underestimated total EI when compared to the DLW method among preschoolers. Further refinement of the RFPM is needed for assessing the EI of young children.

Biomarker-predicted sugars intake compared with self-reported measures in US Hispanics/Latinos: results from the HCHS/SOL SOLNAS study

OBJECTIVE

Measurement error in self-reported total sugars intake may obscure associations between sugars consumption and health outcomes, and the sum of 24 h urinary sucrose and fructose may serve as a predictive biomarker of total sugars intake.

DESIGN

The Study of Latinos: Nutrition & Physical Activity Assessment Study (SOLNAS) was an ancillary study to the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) cohort. Doubly labelled water and 24 h urinary sucrose and fructose were used as biomarkers of energy and sugars intake, respectively. Participants' diets were assessed by up to three 24 h recalls (88 % had two or more recalls). Procedures were repeated approximately 6 months after the initial visit among a subset of ninety-six participants.

SETTING

Four centres (Bronx, NY; Chicago, IL; Miami, FL; San Diego, CA) across the USA.

SUBJECTS

Men and women (n 477) aged 18-74 years.

RESULTS

The geometric mean of total sugars was 167·5 (95 % CI 154·4, 181·7) g/d for the biomarker-predicted and 90·6 (95 % CI 87·6, 93·6) g/d for the self-reported total sugars intake. Self-reported total sugars intake was not correlated with biomarker-predicted sugars intake (r=-0·06, P=0·20, n 450). Among the reliability sample (n 90), the reproducibility coefficient was 0·59 for biomarker-predicted and 0·20 for self-reported total sugars intake.

CONCLUSIONS

Possible explanations for the lack of association between biomarker-predicted and self-reported sugars intake include measurement error in self-reported diet, high intra-individual variability in sugars intake, and/or urinary sucrose and fructose may not be a suitable proxy for total sugars intake in this study population.

Dilution space ratio of 2H and 18O of doubly labeled water method in humans

Variation of the dilution space ratio (Nd/No) between deuterium ((2)H) and oxygen-18 ((18)O) impacts the calculation of total energy expenditure (TEE) by doubly labeled water (DLW). Our aim was to examine the physiological and methodological sources of variation of Nd/No in humans. We analyzed data from 2,297 humans (0.25-89 yr old). This included the variables Nd/No, total body water, TEE, body mass index (BMI), and percent body fat (%fat). To differentiate between physiologic and methodologic sources of variation, the urine samples from 54 subjects were divided and blinded and analyzed separately, and repeated DLW dosing was performed in an additional 55 participants after 6 mo. Sex, BMI, and %fat did not significantly affect Nd/No, for which the interindividual SD was 0.017. The measurement error from the duplicate urine sample sets was 0.010, and intraindividual SD of Nd/No in repeats experiments was 0.013. An additional SD of 0.008 was contributed by calibration of the DLW dose water. The variation of measured Nd/No in humans was distributed within a small range and measurement error accounted for 68% of this variation. There was no evidence that Nd/No differed with respect to sex, BMI, and age between 1 and 80 yr, and thus use of a constant value is suggested to minimize the effect of stable isotope analysis error on calculation of TEE in the DLW studies in humans. Based on a review of 103 publications, the average dilution space ratio is 1.036 for individuals between 1 and 80 yr of age.

Accelerometer-based Physical Activity Monitoring in Patients with Knee Osteoarthritis: Objective and Ambulatory Assessment of Actual Physical Activity During Daily Life Circumstances

Background:

It is important to assess physical activity objectively during daily life circumstances, to understand the association between physical activity and diseases and to determine the effectiveness of interventions. Accelerometer-based physical activity monitoring seems a promising method and could potentially capture all four FITT (i.e. Frequency, Intensity, Time, Type) components of physical activity considered by the World Health Organization (WHO).

Aim:

To assess the four FITT components of physical activity with an accelerometer during daily life circumstances and compare with self-reported levels of physical activity in patients with knee osteoarthritis (OA) and a healthy control group.

Methods:

Patients (n=30) with end-stage knee OA and age-matched healthy subjects (n=30) were measured. An ambulant tri-axial accelerometer was placed onto the lateral side of the upper leg. Physical activity was measured during four consecutive days. Using algorithm-based peak detection methods in Matlab, parameters covering the four FITT components were assessed. Self-reported physical activity was assessed using the Short questionnaire to assess health enhancing physical activity (SQUASH).

Results:

Knee OA patients demonstrated fewer walking bouts (154 ±79 versus 215 ±65 resp.; p=0.002), step counts (4402 ±2960 steps/day versus 6943 ±2581 steps/day; p=0.001) and sit-to-stand (STS) transfers (37 ±14 versus 44 ±12; p=0.031) compared to controls. Knee OA patients demonstrated more time sitting (65 ±15% versus 57 ±10% resp.; p=0.029), less time walking (8 ±4% versus 11 ±4% resp.; p=0.014) and lower walking cadence (87 ±11steps/min versus 99 ± 8steps/min resp.; p<0.001). Accelerometer-based parameters of physical activity were moderately-strong (Pearsons’s r= 0.28-0.49) correlated to self-reported SQUASH scores.

Conclusion:

A single ambulant accelerometer-based physical activity monitor feasibly captures the four FITT components of physical activity and provides more insight into the actual physical activity behavior and limitations of knee OA patients in their daily life.

Low Levels of Energy Expenditure in Childhood Cancer Survivors: Implications for Obesity Prevention

Childhood cancer survivors are at an increased risk of obesity but causes for this elevated risk are uncertain. We evaluated total energy expenditure in childhood cancer survivors using the doubly labeled water method in a cross-sectional study of 17 survivors of pediatric leukemia or lymphoma (median age, 11.5 y). Mean total energy expenditure was 2073 kcal/d, which was nearly 500 kcal/d lower than estimated energy requirements with recommended levels of physical activity. This energy gap is likely to contribute to the risk of obesity in this population and future trials are needed to assess implications and potential treatment strategies.

Study design of the Maycoba Project: obesity and diabetes in Mexican Pimas

OBJECTIVE

To focus on the rationale and methods of the Maycoba Project.

METHODS

Study population included Mexican Pima Indians (MPI) and Blancos aged ≥20-years, living in the village of Maycoba and surrounding area. Surveys in 1995 and 2010 included a medical history, biochemical and anthropomet- ric measurements. Additionally, socio- economic, physical activity, and dietary interviews were conducted. The 2010 study incorporated investigations on type 2 diabetes (T2D) and obesity-associated genetic alleles and human-envi- ronment changes.

RESULTS

The study results are limited to demographic data and description of the eligible and ex- amined sample.

CONCLUSIONS

This study may yield important information on T2D and obesity etiology in a traditional population exposed to environmental changes.

The doubly labeled water method produces highly reproducible longitudinal results in nutrition studies

The doubly labeled water (DLW) method is considered the reference method for the measurement of energy expenditure under free-living conditions. However, the reproducibility of the DLW method in longitudinal studies is not well documented. This study was designed to evaluate the longitudinal reproducibility of the DLW method using 2 protocols developed and implemented in a multicenter clinical trial-the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE). To document the longitudinal reproducibility of the DLW method, 2 protocols, 1 based on repeated analysis of dose dilutions over the course of the clinical trial (dose-dilution protocol) and 1 based on repeated but blinded analysis of randomly selected DLW studies (test-retest protocol), were carried out. The dose-dilution protocol showed that the theoretical fractional turnover rates for (2)H and (18)O and the difference between the 2 fractional turnover rates were reproducible to within 1% and 5%, respectively, over 4.5 y. The Bland-Altman pair-wise comparisons of the results generated from 50 test-retest DLW studies showed that the fractional turnover rates and isotope dilution spaces for (2)H and (18)O, and total energy expenditure, were highly reproducible over 2.4 y. Our results show that the DLW method is reproducible in longitudinal studies and confirm the validity of this method to measure energy expenditure, define energy intake prescriptions, and monitor adherence and body composition changes over the period of 2.5-4.4 y. The 2 protocols can be adopted by other laboratories to document the longitudinal reproducibility of their measurements to ensure the long-term outcomes of interest are meaningful biologically. This trial was registered at clinicaltrials.gov as NCT00427193.

Determinants of Free-Living Energy Expenditure in Normal Weight and Obese Women Measured by Doubly Labeled Water

Total free-living energy expenditure (TEE) was measured in 9 normal weight controls and 5 obese women using the doubly labeled water (DLW) method. Resting energy expenditure (REE) and the thermic effect of food (TEF) were measured by indirect calorimetry and the energy cost of physical activity (PA) calculated by deduction, in order to quantify the components and identify determinants of free-living TEE. Although REE was quantitatively the major component of TEE in both groups, PA best explained the variability, contributing 76% to the variance in free-living TEE. The obese women had elevated values for TEE (12397 +/- 2565 vs. 8339 +/- 1787 kJ/d, mean +/- SD; p < 0.005), compared with the control women. PA (5071 +/- 2385 vs. 2552 +/- 1452; p < 0.05) and REE (6393 +/- 678 vs. 5084 +/- 259; p < 0.0005) were also raised in the obese, whereas TEF was not significantly different between the groups, accounting for 7.6% of energy expenditure for the obese and 8% for the control subjects. Body weight was the single best determinant of mean daily free-living TEE across both groups. We conclude that PA and body weight are the main determinants of free-living TEE.

Assessment tools in obesity - psychological measures, diet, activity, and body composition

The global increase in the prevalence of obesity has led to an increased need for measurement tools for research, management and treatment of the obese person. The physical size limitations imposed by obesity, variations in body composition from that of normal weight, and a complex psychopathology all pose tremendous challenges to the assessment of an obese person. There is little published research regarding what tools can be used with confidence. This review is designed to provide researchers and clinicians with a guide to the current and emerging measurement tools specifically associated with obesity research and practice. Section 1 addresses psychological measures of well being. Sections 2, 3, and 4 focus on the assessment of food intake, activity, and body composition. All sections address basic challenges involved in the study and management of obesity, and highlight methodological issues associated with the use of common assessment tools. The best available methods for use in the obese both in research and clinical practice are recommended.

Between-monitor differences in step counts are related to body size: implications for objective physical activity measurement

Background

The quantification of the relationships between walking and health requires that walking is measured accurately. We correlated different measures of step accumulation to body size, overall physical activity level, and glucose regulation.

Methods

Participants were 25 men and 25 women American Indians without diabetes (Age: 20-34 years) in Phoenix, Arizona, USA. We assessed steps/day during 7 days of free living, simultaneously with three different monitors (Accusplit-AX120, MTI-ActiGraph, and Dynastream-AMP). We assessed total physical activity during free-living with doubly labeled water combined with resting metabolic rate measured by expired gas indirect calorimetry. Glucose tolerance was determined during an oral glucose tolerance test.

Findings

Based on observed counts in the laboratory, the AMP was the most accurate device, followed by the MTI and the AX120, respectively. The estimated energy cost of 1000 steps per day was lower in the AX120 than the MTI or AMP. The correlation between AX120-assessed steps/day and waist circumference was significantly higher than the correlation between AMP steps and waist circumference. The difference in steps per day between the AX120 and both the AMP and the MTI were significantly related to waist circumference.

Interpretation

Between-monitor differences in step counts influence the observed relationship between walking and obesity-related traits.

The usefulness of an accelerometer for monitoring total energy expenditure and its clinical application for predicting body weight changes in type 2 diabetic korean women

BACKGROUND

The purpose of this study was to evaluate the usefulness of an accelerometer in predicting body weight (BW) change during a lifestyle intervention and to find out whether exercise or overall physical activity is associated with change in insulin sensitivity and body composition.

METHODS

A total of 49 overweight (body mass index [BMI] ≥ 23 kg/m(2)) women with diabetes were enrolled and performed lifestyle intervention while monitoring BW, total energy expenditure (TEE) and physical activity energy expenditure (PAEE) using an accelerometer, and energy intake (EI) using a three-day dietary record at baseline and every 2 weeks for 12 weeks. We assessed body composition using bioimpedance analysis and compared the actual BW change to the predicted BW change, which was calculated from the energy deficit (ED) between EI and TEE (ED = EI-TEE).

RESULTS

Mean age was 57.2 years, duration of diabetes was 8.0 years, and BMI was 27.8 kg/m(2). There was no significant difference between EI and TEE at baseline. For 12 weeks, the ED was 474.0 kcal·day(-1), which was significantly correlated with BW change (-3.1 kg) (r = 0.725, P < 0.001). However, the actual BW change was 50% lower than the predicted BW change. Both TEE and PAEE correlated with change in K(ITT) (r = 0.334, P = 0.019; r = 0.358, P = 0.012, respectively), BMI (r = -0.395, P = 0.005; r = -0.347, P = 0.015, respectively), and fat mass (r = -0.383, P = 0.007; r = -0.395, P = 0.005, respectively), but only TEE correlated with fat free mass change (r = -0.314, P = 0.030).

CONCLUSION

The accelerometer appears to be a useful tool for measuring TEE under free-living conditions for both short- and long-term periods.

A stable isotope method for the simultaneous measurement of matrix synthesis and cell proliferation in articular cartilage in vivo

OBJECTIVE

Measurements of cell proliferation and matrix synthesis in cartilage explants have identified regulatory factors [e.g., interleukin-1 (IL-1)] that contribute to osteoarthritis and anabolic mediators [e.g., bone morphogenic protein-7 (BMP-7)] that may have therapeutic potential. The objective of this study was to develop a robust method for measuring cell proliferation and glycosaminoglycan synthesis in articular cartilage that could be applied in vivo.

METHODS

A stable isotope-mass spectrometry approach was validated by measuring the metabolic effects of IL-1 and BMP-7 in cultures of mature and immature bovine cartilage explants. The method was also applied in vivo to quantify physiologic turnover rates of matrix and cells in the articular cartilage of normal rats. Heavy water was administered to explants in the culture medium and to rats via drinking water, and cartilage was analyzed for labeling of chondroitin sulfate (CS), hyaluronic acid (HA) and DNA.

RESULTS

As expected, IL-1 inhibited the synthesis of DNA and CS in cartilage explants. However, IL-1 inhibited HA synthesis only in immature cartilage. Furthermore, BMP-7 was generally stimulatory, but immature cartilage was significantly more responsive than mature cartilage, particularly in terms of HA and DNA synthesis. In vivo, labeling of CS and DNA in normal rats for up to a year indicated half-lives of 22 and 862 days, respectively, in the joint.

CONCLUSIONS

We describe a method by which deuterium from heavy water is traced into multiple metabolites from a single cartilage specimen to profile its metabolic activity. This method was demonstrated in tissue culture and rodents but may have significant clinical applications.

Physical activity in aging: comparison among young, aged, and nonagenarian individuals

Physical activity (PA) is known to decline with age; however, there is a paucity of data on activity in persons who are in their nineties and beyond. We used objective and reliable methods to measure PA in nonagenarians (>or=90 yr; n=98) and hypothesized that activity would be similar to that of aged (60-74 yr; n=58) subjects but less than in young (20-34 yr; n=53) volunteers. Total energy expenditure (TEE) was measured by doubly labeled water over 14 days and resting metabolic rate (RMR) by indirect calorimetry. Measures of PA included activity energy expenditure adjusted for body composition, TEE adjusted for RMR, physical activity level (PAL), and activity over 14 days by accelerometry expressed as average daily durations of light and moderate activity. RMR and TEE were lower with increasing age group (P<0.01); however, RMR was not different between aged and nonagenarian subjects after adjusting for fat-free mass, fat mass, and sex. Nonagenarians had a lower PAL and were more sedentary than the aged and young groups (P<0.01); however, the nonagenarians who were more active on a daily basis walked further during a timed test, indicating higher physical functionality. For all measures of activity, no differences were found between young and aged volunteers. PA was markedly lower in nonagenarians compared with young and aged adults. Interestingly, PA was similar between young volunteers and those who were in their 60s and 70s, likely due to the sedentary nature of our society, particularly in young adults.

Validation study of energy expenditure and intake during calorie restriction using doubly labeled water and changes in body composition

BACKGROUND

Clinical trials involving calorie restriction (CR) require an assessment of adherence to a prescribed CR with the use of an objective measure of energy intake (EI).

OBJECTIVE

The objective was to validate the use of energy expenditure (EE) measured by doubly labeled water (DLW), in conjunction with precise measures of body composition, to calculate an individual's EI during 30% CR.

DESIGN

Ten participants underwent 30% CR for 3 wk. During the last week (7 d), 24-h EE was measured in a respiratory chamber and simultaneously by DLW (EEDLW). EI was calculated from 7-d EE measured by DLW and from changes in energy stores (ES) (weight and body composition). Calculated EI was then compared with the actual EI measured in the chamber by using the following equations: calculated EI (kcal/d) = EEDLW + DeltaES, where DeltaESFM/FFM (kcal/d) = (9.3 x DeltaFM, g/d) + (1.1 x DeltaFFM, g/d), FM is fat mass, and FFM is fat-free mass.

RESULTS

We found close agreement (R = 0.88) between EE measured in the metabolic chamber and EEDLW during CR. Using the measured respiratory quotient, we found that the mean (+/-SD) EE(DLW) was 1934 +/- 377 kcal/d and EE measured in the metabolic chamber was 1906 +/- 327 kcal/d, ie, a 1.3 +/- 8.9% overestimation. EI calculated from EEDLW and from changes in ES was 8.7 +/- 36.7% higher than the actual EI provided during the chamber stay (1596 +/- 656 kcal/d).

CONCLUSIONS

DLW methods can accurately estimate 24-h EE during CR. Although the mean difference between actual and calculated EIs for the group was small, we conclude that the interindividual variability was too large to provide an assessment of CR adherence on an individual basis.

Assessing risk factors for obesity between childhood and adolescence: II. Energy metabolism and physical activity

OBJECTIVE

To assess the effect of energy expenditure, including resting metabolic rate (RMR), total energy expenditure (TEE), and activity energy expenditure (AEE), as well as substrate oxidation (respiratory quotient [RQ]), on the development of obesity in a large cohort of Native American children with a high propensity for obesity.

METHODS

During the summer months of 1992 to 1995 and again 5 years later, 138 (65 boys and 73 girls) 5-year-old Pima Indian children were studied. At baseline and follow-up, height and weight were measured; body composition was assessed with the use of 18O dilution; RMR and RQ were assessed with the use of indirect calorimetry; TEE was measured with the use of the doubly-labeled water method; and AEE was calculated (TEE - [RMR + 0.1 x TEE]). In addition, an activity questionnaire was used to assess participation in sporting activities as well as television viewing during the previous year. Linear regression models were used to assess the effects of the baseline variables on the development of obesity.

RESULTS

Pima Indian children were markedly overweight at both 5 and 10 years of age. Cross-sectionally, percentage of body fat and body weight at 5 and 10 years of age were negatively correlated with sports participation and positively correlated with television viewing. Most important, there was a marked change in the correlation between body size and activity between 5 and 10 years of age: at age 5 years, weight was positively correlated with AEE and PAL, but at age 10 years, the correlation with AEE was lost and that with PAL was negative. However, prospectively, none of the variables measured at baseline was a predictor of percentage of body fat at age 10 years after adjustment for percentage of body fat at age 5 years.

CONCLUSIONS

At age 5 years, obesity is associated with decreased participation in sports and increased television viewing but not with a decreased PAL. At age 10 years, obesity is associated with decreased participation in sports, increased television viewing, and a decreased PAL, suggesting that a decrease in PAL in free-living conditions seems to follow, not precede, the development of obesity.

Influence of delayed isotopic equilibration in urine on the accuracy of the (2)H(2)(18)O method in the elderly

Isotopic determination of total energy expenditure (TEE) by the doubly labeled water (DLW) method may be affected by urine retention in the elderly. The isotopic enrichments in urine and plasma sampled simultaneously 4 h post-DLW dose were compared in a subset of 281 subjects [139 women, 142 men, 75 +/- 3 (SD) yr] of the 3,075 participants in the Health, Aging, and Body Composition study. Based on analytic precisions, a +/- 2% urine-plasma difference was set as the cut-off value. Ten percent of the population presented a difference lower than -2%, suggesting a delay in urine isotopic equilibration. This -13 +/- 10% urine-plasma difference was not linked to analytic errors, illnesses, the sampling time, or the time and quantity of water intake, suggesting that urine retention may be the main factor. The consequences are an 18 +/- 13 and 21 +/- 16% overestimation of the total body water and the TEE, respectively. Unexpectedly, 21% of the population presented a urine-plasma difference higher than +/- 2% that resulted, however, in a nonsignificant TEE underestimation of -3 +/- 5%. In conclusion, the delayed isotopic equilibration observed in urine reduces the accuracy of the DLW method in the elderly. It is recommended, when blood sampling is impossible, to adopt the intercept method with urine sampling 24 h postdose.

Canadian recommended nutrient intakes underestimate true energy requirements in middle-aged women

To examine whether Health Canada's Recommended Nutrient Intakes (RNI) and FAO/WHO/UNU (Food and Agriculture Organization, World Health Organization, United Nations University) values provide accurate indices of true energy requirements, energy expenditure was determined using doubly labelled water (DLW) over 13 days in a group of 29 middle-aged women. Energy intakes were calculated from weighed food intake, and energy expenditures and intakes were then compared with individual calculated RNI requirements. The mean energy requirement as determined by DLW expenditure (9.56 +/- 0.53 MJ/d) was higher (p < 0.0001) than reported energy intake (7.08 +/- 0.30 MJ/d) and was higher (p < 0.004) than RNI mean energy requirement (7.97 +/- 0.18 MJ/d). The mean RNI for energy was also lower (p < 0.0001) than that derived from FAO data. These results suggest that current Health Canada RNIs are inadequate in predicting the energy needs of Canadian middle-aged women.

Total energy expenditure and the level of physical activity correlate with plasma leptin concentrations in five-year-old children

Leptin, the product of the ob gene, is a hormone secreted by adipocytes that is known to decrease food intake and increase energy expenditure in ob/ob mice. In humans, variants in the OB gene have not been detected and very little is known about the action of leptin on food intake and energy expenditure, although circulating leptin concentrations are positively correlated to body fat stores. The purpose of this study was to assess the relationship between fasting plasma leptin concentrations and energy expenditure in 123 5-yr-old Pima Indian children (67 males/76 females). Body composition was assessed by isotopic water dilution (18O) whereas total energy expenditure (TEE) and resting metabolic rate (RMR) were measured using doubly labeled water and indirect calorimetry, respectively. The physical activity level was calculated as the ratio of TEE:RMR. Plasma leptin concentrations were positively correlated to percent body fat (r = 0.84, P < 0.0001), but were similar in boys and girls after adjusting for percent body fat. Most importantly, we found that, independent of the percentage of body fat, plasma leptin concentrations correlated with TEE (in absolute values, r = 0.37, P < 0.0001, or adjusted for body size r = 0.42; P < 0.0001) and with physical activity level (r = 0.26, P < 0.01), but not RMR. These results suggest that, as in animal models, leptin plays a role in energy expenditure in humans.

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.