Human energy expenditure: advances in organ-tissue prediction models

Humans expend energy at rest (REE), and this major energy exchange component is now usually estimated using statistical equations that include weight and other predictor variables. While these formulas are useful in evaluating an individual's or group's REE, an important gap remains: available statistical models are inadequate for explaining underlying organ-specific and tissue-specific mechanisms accounting for resting heat production. The lack of such systems level REE prediction models leaves many research questions unanswered. A potential approach that can fill this gap began with investigators who first showed in animals and later in humans that REE reflects the summated heat production rates of individual organs and tissues. Today, using advanced imaging technologies, REE can be accurately estimated from the measured in vivo mass of 10 organ-tissue mass components combined with their respective mass-specific metabolic rates. This review examines the next frontier of energy expenditure models and discusses how organ-tissue models have the potential not only to better predict REE but also to provide insights into how perturbations in organ mass lead to structure-function changes across other interacting organ systems. The introductory ideas advanced in this review provide a framework for future human energy expenditure modelling research.

A review of machine learning in obesity

Rich sources of obesity-related data arising from sensors, smartphone apps, electronic medical health records and insurance data can bring new insights for understanding, preventing and treating obesity. For such large datasets, machine learning provides sophisticated and elegant tools to describe, classify and predict obesity-related risks and outcomes. Here, we review machine learning methods that predict and/or classify such as linear and logistic regression, artificial neural networks, deep learning and decision tree analysis. We also review methods that describe and characterize data such as cluster analysis, principal component analysis, network science and topological data analysis. We introduce each method with a high-level overview followed by examples of successful applications. The algorithms were then applied to National Health and Nutrition Examination Survey to demonstrate methodology, utility and outcomes. The strengths and limitations of each method were also evaluated. This summary of machine learning algorithms provides a unique overview of the state of data analysis applied specifically to obesity.

Clinically applicable optical imaging technology for body size and shape analysis: comparison of systems differing in design

BACKGROUND/OBJECTIVES

Recent advances have extended anthropometry beyond flexible tape measurements to automated three-dimensional optical devices that rapidly acquire hundreds of body surface dimensions. Three new devices were recently introduced that share in common inexpensive optical cameras. The design, and thus potential clinical applicability, of these systems differ substantially leading us to critically evaluate their accuracy and precision.

SUBJECTS/METHODS

113 adult subjects completed evaluations by the three optical devices (KX-16 (16 stationary cameras), Proscanner (1 vertically oscillating camera), and Styku scanner (1 stationary camera)), air displacement plethysmography (ADP), dual-energy X-ray absorptiometry (DXA) and a flexible tape measure. Optical measurements were compared to reference method estimates that included results acquired by flexible tape, DXA and ADP.

RESULTS

Optical devices provided respective circumference and regional volume estimates that overall were well-correlated with those obtained from flexible tape measurements (for example, hip circumference: R2, 0.91, 0.90, 0.96 for the KX-16, Proscanner, and Styku scanner, respectively) and DXA (for example, trunk volume: R2, 0.97, 0.97, and 0.98). Total body volumes measured by the optical devices were highly correlated with those from the ADP system (all R2s, 0.99). Coefficient of variations obtained from duplicate measurements (n, 55) were larger in optical than in reference measurements and significant (P<0.05) bias was present for some optical measurements relative to reference method estimates.

CONCLUSIONS

Overall, the evaluated optical imaging systems differing in design provided body surface measurements that compared favorably with corresponding reference methods. However, our evaluations uncovered system measurement limitations, such as discrepancies in landmarking, that with correction have the potential to improve future developed devices.

Why are there race/ethnic differences in adult body mass index-adiposity relationships? A quantitative critical review

Body mass index (BMI) is now the most widely used measure of adiposity on a global scale. Nevertheless, intense discussion centers on the appropriateness of BMI as a phenotypic marker of adiposity across populations differing in race and ethnicity. BMI-adiposity relations appear to vary significantly across race/ethnic groups, but a collective critical analysis of these effects establishing their magnitude and underlying body shape/composition basis is lacking. Accordingly, we systematically review the magnitude of these race-ethnic differences across non-Hispanic (NH) white, NH black and Mexican American adults, their anatomic body composition basis and potential biologically linked mechanisms, using both earlier publications and new analyses from the US National Health and Nutrition Examination Survey. Our collective observations provide a new framework for critically evaluating the quantitative relations between BMI and adiposity across groups differing in race and ethnicity; reveal new insights into BMI as a measure of adiposity across the adult age-span; identify knowledge gaps that can form the basis of future research and create a quantitative foundation for developing BMI-related public health recommendations.

Prediction of percent body fat measurements in Americans 8 years and older

BACKGROUND/OBJECTIVES

Although numerous equations to predict percent body fat have been published, few have broad generalizability. The objective of this study was to develop sets of equations that are generalizable to the American population 8 years of age and older.

SUBJECTS/METHODS

Dual-emission X-ray absorptiometry (DXA) assessed percent body fat from the 1999-2006 National Health and Nutrition Examination Survey (NHANES) was used as the response variable for development of 14 equations for each gender that included between 2 and 10 anthropometrics. Other candidate variables included demographics and menses. Models were developed using the Least Absolute Shrinkage and Selection Operator (LAASO) and validated in a ¼ withheld sample randomly selected from 11 884 males or 9215 females.

RESULTS

In the final models, R(2) ranged from 0.664 to 0.845 in males and from 0.748 to 0.809 in females. R(2) was not notably improved by development of equations within, rather than across, age and ethnic groups. Systematic over or under estimation of percent body fat by age and ethnic groups was within 1 percentage point. Seven of the fourteen gender-specific models had R(2) values above 0.80 in males and 0.795 in females and exhibited low bias by age, race/ethnicity and body mass index (BMI).

CONCLUSIONS

To our knowledge, these are the first equations that have been shown to be valid and unbiased in both youth and adults in estimating DXA assessed body fat. The equations developed here are appropriate for use in multiple ethnic groups, are generalizable to the US population and provide a useful method for assessment of percent body fat in settings where methods such as DXA are not feasible.

Automated anthropometric phenotyping with novel Kinect-based three-dimensional imaging method: comparison with a reference laser imaging system

BACKGROUND/OBJECTIVES

Anthropometry for measuring body composition, shape, surface area and volume is important for human clinical research and practice. Although training and technical skills are required for traditional tape and caliper anthropometry, a new opportunity exists for automated measurement using newly developed relatively low-cost three-dimensional (3D) imaging devices. The aim of this study was to compare results provided by a Kinect-based device to a traditional laser 3D reference system.

SUBJECTS/METHODS

Measurements made by the evaluated device, a hybrid of commercially purchased hardware (KX-16; TC(2), Cary, NC, USA) with our additional added software, were compared with those derived by a high-resolution laser scanner (Vitus Smart XXL; Human Solutions North America, Cary, NC, USA). Both imaging systems were compared with additional linear (stadiometer-derived height) and volumetric (total volume, air-displacement plethysmography) measurements. Subjects (n=101) were healthy children (age ≥5 years) and adults varying in body mass index.

RESULTS

Representative linear (4), circumferential (6), volumetric (3) and surface area (1) measurements made by the Kinect-based device showed a consistent pattern relative to the laser system: high correlations (R(2)s= 0.70-0.99, all P<0.001); 1-3% differences for large linear (for example, height, X±s.d., -1.4±0.5%), circumferential (for example, waist circumference, -2.1±1.8%), volume (for example, total body, -0.8±2.2%) and surface area (whole-body, -1.7±2.0%) estimates. By contrast, mean measurement differences were substantially larger for small structures (for example, forearm volume, 31.3±31.4%).

CONCLUSIONS

Low-cost 3D Kinect-based imaging systems have the potential for providing automated accurate anthropometric and related body measurements for relatively large components; further hardware and software developments may be able to improve system small-component resolution.

Energy balance measurement: when something is not better than nothing

Energy intake (EI) and physical activity energy expenditure (PAEE) are key modifiable determinants of energy balance, traditionally assessed by self-report despite its repeated demonstration of considerable inaccuracies. We argue here that it is time to move from the common view that self-reports of EI and PAEE are imperfect, but nevertheless deserving of use, to a view commensurate with the evidence that self-reports of EI and PAEE are so poor that they are wholly unacceptable for scientific research on EI and PAEE. While new strategies for objectively determining energy balance are in their infancy, it is unacceptable to use decidedly inaccurate instruments, which may misguide health-care policies, future research and clinical judgment. The scientific and medical communities should discontinue reliance on self-reported EI and PAEE. Researchers and sponsors should develop objective measures of energy balance.

Functional body composition and related aspects in research on obesity and cachexia: report on the 12th Stock Conference held on 6 and 7 September 2013 in Hamburg, Germany

The 12th Stock Conference addressed body composition and related functions in two extreme situations, obesity and cancer cachexia. The concept of 'functional body composition' integrates body components into regulatory systems relating the mass of organs and tissues to corresponding in vivo functions and metabolic processes. This concept adds to an understanding of organ/tissue mass and function in the context of metabolic adaptations to weight change and disease. During weight gain and loss, there are associated changes in individual body components while the relationships between organ and tissue mass are fixed. Thus an understanding of body weight regulation involves an examination of the relationships between organs and tissues rather than individual organ and tissue masses only. The between organ/tissue mass relationships are associated with and explained by crosstalks between organs and tissues mediated by cytokines, hormones and metabolites that are coupled with changes in body weight, composition and function as observed in obesity and cancer cachexia. In addition to established roles in intermediary metabolism, cell function and inflammation, organ-tissue crosstalk mediators are determinants of body composition and its change with weight gain and loss. The 12th Stock Conference supported Michael Stocks' concept of gaining new insights by integrating research ideas from obesity and cancer cachexia. The conference presentations provide an in-depth understanding of body composition and metabolism.

Weight loss composition is one-fourth fat-free mass: a critical review and critique of this widely cited rule

Maximizing fat loss while preserving lean tissue mass and function is a central goal of modern obesity treatments. A widely cited rule guiding expected loss of lean tissue as fat-free mass (FFM) states that approximately one-fourth of weight loss will be FFM (i.e. ΔFFM/ΔWeight = ∼0.25), with the remaining three-fourths being fat mass. This review examines the dynamic relationships between FFM, fat mass and weight changes that follow induction of negative energy balance with hypocaloric dieting and/or exercise. Historical developments in the field are traced with the 'Quarter FFM Rule' used as a framework to examine evolving concepts on obesity tissue, excess weight and what is often cited as 'Forbes' Rule'. Temporal effects in the fractional contribution of FFM to changes in body weight are examined as are lean tissue moderating effects such as ageing, inactivity and exercise that frequently accompany structured low-calorie diet weight loss protocols. Losses of lean tissue with dieting typically tend to be small, raising questions about study design, power and applied measurement method reliability. Our review elicits important questions related to the fractional loss of lean tissues with dieting and provides a foundation for future research on this topic.

Can a weight loss of one pound a week be achieved with a 3500-kcal deficit? Commentary on a commonly accepted rule

Despite theoretical evidence that the model commonly referred to as the 3500-kcal rule grossly overestimates actual weight loss, widespread application of the 3500-kcal formula continues to appear in textbooks, on respected government- and health-related websites, and scientific research publications. Here we demonstrate the risk of applying the 3500-kcal rule even as a convenient estimate by comparing predicted against actual weight loss in seven weight loss experiments conducted in confinement under total supervision or objectively measured energy intake. We offer three newly developed, downloadable applications housed in Microsoft Excel and Java, which simulates a rigorously validated, dynamic model of weight change. The first two tools available at http://www.pbrc.edu/sswcp, provide a convenient alternative method for providing patients with projected weight loss/gain estimates in response to changes in dietary intake. The second tool, which can be downloaded from the URL http://www.pbrc.edu/mswcp, projects estimated weight loss simultaneously for multiple subjects. This tool was developed to inform weight change experimental design and analysis. While complex dynamic models may not be directly tractable, the newly developed tools offer the opportunity to deliver dynamic model predictions as a convenient and significantly more accurate alternative to the 3500-kcal rule.

Evolving concepts on adjusting human resting energy expenditure measurements for body size

Establishing if an adult's resting energy expenditure (REE) is high or low for their body size is a pervasive question in nutrition research. Early workers applied body mass and height as size measures and formulated the Surface Law and Kleiber's Law, although each has limitations when adjusting REE. Body composition methods introduced during the mid-20th century provided a new opportunity to identify metabolically homogeneous 'active' compartments. These compartments all show improved correlations with REE estimates over body mass-height approaches, but collectively share a common limitation: REE-body composition ratios are not 'constant' but vary across men and women and with race, age and body size. The now-accepted alternative to ratio-based norms is to adjust for predictors by applying regression models to calculate 'residuals' that establish if an REE is relatively high or low. The distinguishing feature of statistical REE-body composition models is a 'non-zero' intercept of unknown origin. The recent introduction of imaging methods has allowed development of physiological tissue-organ-based REE prediction models. Herein, we apply these imaging methods to provide a mechanistic explanation, supported by experimental data, for the non-zero intercept phenomenon and, in that context, propose future research directions for establishing between-subject differences in relative energy metabolism.

Why do individuals not lose more weight from an exercise intervention at a defined dose? An energy balance analysis

Weight loss resulting from an exercise intervention tends to be lower than predicted. Modest weight loss can arise from an increase in energy intake, physiological reductions in resting energy expenditure, an increase in lean tissue or a decrease in non-exercise activity. Lower than expected, weight loss could also arise from weak and invalidated assumptions within predictive models. To investigate these causes, we systematically reviewed studies that monitored compliance to exercise prescriptions and measured exercise-induced change in body composition. Changed body energy stores were calculated to determine the deficit between total daily energy intake and energy expenditures. This information combined with available measurements was used to critically evaluate explanations for low exercise-induced weight loss. We conclude that the small magnitude of weight loss observed from the majority of evaluated exercise interventions is primarily due to low doses of prescribed exercise energy expenditures compounded by a concomitant increase in caloric intake.

Can Ethnic Differences in Men's Preferences for Women's Body Shapes Contribute to Ethnic Differences in Female Adiposity?

In the United States, obesity is more common among black and Hispanic than white women. One putative cause of this difference is different cultural norms for attractiveness. Two studies assessed ethnic differences in men's perceptions of the attractiveness of females of varying sizes. In the first, 108 men recruited on the New York subway were shown sets of silhouettes depicting female bodies varying in fatness and were asked to pick the silhouette they found most attractive. They were also asked to indicate the thinnest and fattest figures they would consider dating. A measure of "latitude of acceptance" was computed as the difference between the thinnest and fattest figures considered. Results indicated no relationship between ethnicity and preference (F = 1.383, p = .257) or "latitude" (F = .102, p = .903). In Study 2, "personal advertisements" placed by 373 black, 1915 white, 110 Hispanic, and 30 Asian men from 35 newspapers and magazines were coded as: 1) thinness preferred; 2) no information on weight preference; 3) fatness preferred; or 4) states weight or looks unimportant. Results indicated a statistically significant but small association between ethnicity and preference (chi2 = 49.55, df = 9, p < .00001). Relative to white and Asian men, black and Hispanic men more frequently requested fat women, Hispanic men less frequently requested thin women, and black men more frequently stated that looks or weight did not matter. Ethnicity explained only 2.1% of the variance in preference. Thus, it seems unlikely that ethnic differences in men's preferences for women's body shapes contribute substantially to ethnic differences in female adiposity.

Evidence of Commingling in Human Eating Behavior

This investigation tested whether distributions of certain aspects of eating behavior were consistent with the notion of a "mixture model;" that is, two or more distinct commingled component distributions, consistent with the possibility of major gene action. Undergraduates (n=901) completed self-report trait measures of hunger, disinhibition, and dietary restraint. Variables were residualized for gender and age and transformed to remove skewness. Residualized transformed distributions were tested for departure from unimodality with Hartigan's dip statistic. The distributions of all three aspects of eating behavior were significantly non-unimodal. Next, component multivariate normal distributions were estimated via maximum likelihood. Likelihood ratio tests were employed to compare nested models. A mixture of four distributions with unequal variance-covariance matrices fit significantly better than any more parsimonious model. In sum, these data strongly suggest that the distributions of several measures of eating behavior are composed of four component distributions. This finding is consistent with the possibility of major gene effects for eating behavior.

A Randomized Double-Blind Crossover Study of the Antiobesity Effects of Etiocholanedione

Etiocholanedione (ED), a natural metabolite of dehydroepiandrosterone, has antiobesity effects in animals when given orally and is nontoxic. We carried out a trial of oral ED in obese humans. In a 20-week randomized double-blind crossover study, 14 subjects lost significantly more weight and body fat during treatment with oral ED, 4 gm daily, than during placebo administration. Mean weight loss during ED administration was 2.8 +/- 5.5 kilograms, which was equivalent to 0.53 +/- 0.91 kilograms per week per 100 kilograms of body fat; mean weight change during placebo administration was essentially zero: +0.21 +/- 4.2 kg, or +0.04 +/- 0.74 kg/wk/100 kg body fat. The difference between the weight changes in the two periods was significant: for delta kg, P < 0.05; for delta kg/wk/100 kg body fat, P < 0.03. Densitometric measurement of body fat content showed that the mean weight loss coincided almost exactly with the mean decrease in fat content; thus, over the 10-week period of ED administration, the mean fat loss was about 5% of the initial body fat content. Three of the obese subjects had strikingly greater fat loss, about 18%, 19%, and 25% of the initial body fat content. There were no significant subjective or objective side effects of ED administration.

MRI-measured pelvic bone marrow adipose tissue is inversely related to DXA-measured bone mineral in younger and older adults

BACKGROUND/OBJECTIVES

Recent research has shown an inverse relationship between bone marrow adipose tissue (BMAT) and bone mineral density (BMD). There is a lack of evidence at the macro-imaging level to establish whether increased BMAT is a cause or effect of bone loss. This cross-sectional study compared the BMAT and BMD relationship between a younger adult group at or approaching peak bone mass (PBM; age 18.0-39.9 years) and an older group with potential bone loss (PoBL; age 40.0-88.0 years).

SUBJECTS/METHODS

Pelvic BMAT was evaluated in 560 healthy men and women with T1-weighted whole-body magnetic resonance imaging. BMD was measured using whole-body dual-energy X-ray absorptiometry.

RESULTS

An inverse correlation was observed between pelvic BMAT and pelvic, total and spine BMD in the younger PBM group (r=-0.419 to -0.461, P<0.001) and in the older PoBL group (r=-0.405 to -0.500, P<0.001). After adjusting for age, sex, ethnicity, menopausal status, total body fat, skeletal muscle, subcutaneous and visceral adipose tissue, neither subject group (younger PBM vs older PoBL) nor its interaction with pelvic BMAT significantly contributed to the regression models with BMD as dependent variable and pelvic BMAT as independent variable (P=0.434-0.928).

CONCLUSIONS

Our findings indicate that an inverse relationship between pelvic BMAT and BMD is present both in younger subjects who have not yet experienced bone loss and also in older subjects. These results provide support at the macro-imaging level for the hypothesis that low BMD may be a result of preferential differentiation of mesenchymal stem cells from osteoblasts to adipocytes.

Ethnic and sex differences in bone marrow adipose tissue and bone mineral density relationship

The relationship between bone marrow adipose tissue and bone mineral density is different between African Americans and Caucasians as well as between men and women. This suggests that the mechanisms that regulate the differentiation and proliferation of bone marrow stromal cells may differ in these populations.

INTRODUCTION

It has long been established that there are ethnic and sex differences in bone mineral density (BMD) and fracture risk. Recent studies suggest that bone marrow adipose tissue (BMAT) may play a role in the pathogenesis of osteoporosis. It is unknown whether ethnic and sex differences exist in the relationship between BMAT and BMD.

METHODS

Pelvic BMAT was evaluated in 455 healthy African American and Caucasian men and women (age 18-88 years) using whole-body T1-weighted magnetic resonance imaging. BMD was measured using whole-body dual-energy X-ray absorptiometry.

RESULTS

A negative correlation was observed between pelvic BMAT and total body BMD or pelvic BMD (r = -0.533, -0.576, respectively; P < 0.001). In multiple regression analyses with BMD as the dependent variable, ethnicity significantly entered the regression models as either an individual term or an interaction with BMAT. Menopausal status significantly entered the regression model with total body BMD as the dependent variable. African Americans had higher total body BMD than Caucasians for the same amount of BMAT, and the ethnic difference for pelvic BMD was greater in those participants with a higher BMAT. Men and premenopausal women had higher total body BMD levels than postmenopausal women for the same amount of BMAT.

CONCLUSIONS

An inverse relationship exists between BMAT and BMD in African American and Caucasian men and women. The observed ethnic and sex differences between BMAT and BMD in the present study suggest the possibility that the mechanisms regulating the differentiation and proliferation of bone marrow stromal cells may differ in these populations.

Relationships of percent body fat and percent trunk fat with bone mineral density among Chinese, black, and white subjects

We examined ethnic difference in the association of body fat and trunk fat with bone mineral density (BMD) among Chinese, white, and black subjects. We found that, with greater body and trunk fat, both white and black subjects were more likely to have a low BMD than Chinese subjects.

INTRODUCTION

Ethnic differences in body fat, abdominal fat distribution, and BMD have been found in previous studies between Chinese and white subjects. However, the associations of body fat and abdominal fat distribution with BMD have not been studied, and whether the ethnic differences have an effect on these associations is unclear.

METHODS

We evaluated 1,147 subjects aged ≥ 18 years (805 Chinese, 193 whites, and 149 blacks). Percent body fat (%BF), percent trunk fat (%TF), and total and regional BMD including that of head, arm, leg, trunk, rib, spine, and pelvis were measured by dual-energy X-ray absorptiometry. Linear regression models were developed to test the association of ethnicity, %BF, and interaction between ethnicity and %BF with BMD. The models were repeated again, replacing %BF with %TF.

RESULTS

Chinese subjects showed lower BMD in total and most regions compared with black and white subjects; however, these differences were eliminated between Chinese and whites within both sexes and between Chinese and black men when age, weight, height, and %BF were added. %BF and %TF were negatively associated with most regional body BMD. The interactions between %BF, %TF, and ethnicity were found in most regional body BMD among Chinese, white, and black subjects for both men and women.

CONCLUSION

Both %BF and %TF have negative associations with BMD. With greater accumulation of %BF and %TF, both white and black subjects may experience a higher risk of low BMD than Chinese subjects.

Intentional weight loss and changes in symptoms of depression: a systematic review and meta-analysis

OBJECTIVE

Obesity is related to increased risk of several health complications, including depression. Many studies have reported improvements in mood with weight loss, but results have been equivocal. The present meta-analysis examined changes in symptoms of depression that were reported in trials of weight loss interventions. Between-groups comparisons of different weight loss methods (for example, lifestyle modification, diet-alone and pharmacotherapy) were examined, as were within-group changes for each treatment type.

METHOD

MEDLINE was searched for articles published between 1950 and January 2009. Several obesity-related terms were intersected with terms related to depression. Results were filtered to return only studies of human subjects, published in English. Of 5971 articles, 394 were randomized controlled trials. Articles were excluded if they did not report mean changes in weight or symptoms of depression, included children or persons with psychiatric disorders (other than depression), or provided insufficient data for analysis. Thirty-one studies (n=7937) were included. Two authors independently extracted a description of each study treatment, sample characteristics, assessment methods and changes in weight and symptoms of depression. Treatments were categorized as lifestyle modification, non-dieting, dietary counseling, diet-alone, exercise-alone, pharmacotherapy, placebo or control interventions.

RESULTS

Random effects models found that lifestyle modification was superior to control and non-dieting interventions for reducing symptoms of depression, and marginally better than dietary counseling and exercise-alone programs. Exercise-alone programs were superior to controls. No differences were found for comparisons of pharmacologic agents and placebos. Within-group analyses found significant reductions in symptoms of depression for nearly all active interventions. A meta-regression found no relationship between changes in weight and changes in symptoms of depression in lifestyle modification interventions.

CONCLUSIONS

On average, obese individuals in weight loss trials experienced reductions in symptoms of depression. Future studies should examine incidence and resolution of clinically significant depressive disorders with weight loss interventions.

Voluntary weight loss: systematic review of early phase body composition changes

Weight loss follows when adult humans enter a phase of negative energy balance brought about by reducing energy intake and/or increasing energy expenditure. The weight loss period is usually viewed as a continuous process, ending when energy equilibrium is achieved at a lower weight or with death following depletion of fuel stores. However, growing evidence supports the expanded view that induction of negative energy balance leads to well-defined physiological effects characterized by three discrete phases (I-III). At present there are no comprehensive reviews of the 'early' phase of weight loss, a gap highlighted by recent interest in rapidly testing new treatments with short-term protocols. Herein we show from earlier reports and with new data that weight loss during phase I is: mathematically quantifiable with a t(1/2) < 1-week and 4- to 6-week duration; includes well-defined rapidly evolving body composition and energy expenditure changes; and is moderated by multiple factors including subject sex and activity level, nutrients ingested at baseline and during the negative energy balance period, and hormone and pharmacologic treatments. Our in depth review collectively characterizes phase I as a distinct weight loss period while revealing important knowledge gaps that can be filled with appropriately designed future studies.

Evidence for prospective associations among depression and obesity in population-based studies

Obesity may lead to depression or be one of its consequences. We reviewed population-based studies in order to, first, identify the most commonly used research methods, and, second, to evaluate the strength of evidence for prospective associations among obesity and depression. We examined 25 studies, of which 10 tested 'obesity-to-depression' pathways, and 15 tested 'depression-to-obesity' pathways. Descriptive statistics summarized the frequency with which various measurements, designs and data analytic strategies were used. We tallied the number of studies that reported any vs. no statistically significant associations, and report on effect sizes, identified moderating variables within reports, and sought common findings across studies. Results indicated considerable methodological heterogeneity in the literature. Depression was assessed by clinical interview in 44% of studies, weight and height were directly measured in 32%, and only 12% used both. In total, 80% of the studies reported significant obesity-to-depression associations, with odds ratios generally in the range of 1.0 to 2.0, while only 53% of the studies reported significant depression-to-obesity associations. Sex was a common moderating variable. Thus, there was good evidence that obesity is prospectively associated with increased depression, with less consistent evidence that depression leads to obesity. Recommendations for future research regarding study samples, measurement and data analysis are provided.

Obesity and non-fatal motor vehicle crash injuries: sex difference effects

Background

Obesity and motor vehicle crash (MVC) injuries are two parallel epidemics in the United States. An important unanswered question is if there are sex differences in the associations between the presence of obesity and non-fatal MVC injuries.

Objectives

To further understand the association between obesity and non-fatal motor vehicle crash injuries, particularly the sex differences in these relations.

Methods

We examined this question by analyzing data from the 2003 to 2007 National Automotive Sampling System Crashworthiness Data System (NASS CDS). A total of 10, 962 drivers who were aged 18 years or older and who survived frontal collision crashes were eligible for study.

Results

Male drivers experienced a lower rate of overall non-fatal MVC injuries than did female drivers (38.1% vs. 52.2%) but a higher rate of severe injuries (0.7% vs. 0.2%). After adjusting for change in velocity (ΔV) during the crashes, obese male drivers showed a much higher risk [logistic coefficients of BMI for moderate, serious, and severe injury are 0.0766, 0.1470, and 0.1792, respectively; all p<0.05] of non-fatal injuries than did non-obese male drivers and these risks increased with injury severity. Non-fatal injury risks were not found to be increased in obese female drivers. The association between obesity and risk of non-fatal injury was much stronger for male drivers than for female drivers.

Conclusion

The higher risk of non-fatal MVC injuries in obese male drivers might result from their different body shape and fat distribution compared with obese female drivers. Our findings should be considered for obesity reduction, traffic safety evaluation and vehicle design for obese male drivers and provide testable hypotheses for future studies.

Body composition and power changes in elite judo athletes

The purpose of this study was to analyse the association between body composition changes, from a weight stable period to prior competition, on upper-body power in judo athletes. 27 top-level male athletes were evaluated at baseline (weight stable period) and 1-3 days before competition, with a time difference of approximately 1 month. Total body and extracellular water were estimated by dilution techniques (deuterium and bromide, respectively) and intracellular water was calculated as the difference. Body composition was assessed by DXA. A power-load spectrum was used to assess upper-body power output in a bench-press position. Comparison of means, bivariate, and partial correlations were used. Results indicate that though no significant mean changes were found in body composition and upper-body power, individual variability was large. Among all body composition changes, only total-body water (r=0.672; p<0.001) and intracellular water (r=0.596; p=0.001) were related to upper-body power variation. These associations remained significant after controlling for weight and arm lean-soft tissue changes (r=0.594, p=0.002 for total-body water; r=0.524, p=0.007 for intracellular water). These findings highlight the need for tracking total-body water, specifically the intracellular compartment in elite judo athletes in order to avoid reductions in upper-body power when a target body weight is desired prior to competition.

A one-year study to assess the safety and efficacy of the CB1R inverse agonist taranabant in overweight and obese patients with type 2 diabetes

AIM

To evaluate the efficacy and safety of taranabant in overweight and obese patients with type 2 diabetes mellitus (T2DM).

METHODS

This was a multicenter, double-blind, randomized, placebo-controlled study in overweight and obese patients with T2DM (ages > or = 18 and < or = 75 years) with a BMI > or = 27 kg/m(2) and < or = 43 kg/m(2) and HbA1c > or =7.0 and < or = 10.0%, who were either not on an antihyperglycaemic agent or on a stable dose of metformin (> or = 1500 mg/day). After a 2-week placebo run-in, patients were randomized to placebo (N = 156) or taranabant 0.5-mg (N = 155), 1-mg (N = 157), or 2-mg (N = 155) once daily for 52 weeks. Primary efficacy endpoints were changes from baseline in body weight (BW) and HbA1c at Week 36, with results at Week 52 being key secondary endpoints.

RESULTS

In the all-patients-treated population, using a last-observation-carried-forward analysis, reductions in BW were -2.5, -3.7, -4.5 and -5.1 kg at Week 36 and -2.4, -4.0, -4.6 and -5.3 kg at Week 52 in the placebo, 0.5-, 1- and 2-mg groups, respectively (all doses significant vs. placebo at both time points). The proportion of patients who lost > or = 5 and > or = 10% of their baseline BW was significantly greater in the 1- and 2-mg groups vs. placebo at Week 36 and all taranabant groups vs. placebo at Week 52. Reductions in HbA1c were -0.40, -0.47, -0.68 and -0.71% at Week 36 and -0.30, -0.43, -0.65 and -0.64% at Week 52, in the placebo, 0.5-, 1- and 2-mg groups, respectively (1- and 2-mg doses significant vs. placebo at both time points). After 52 weeks, the incidences of adverse experiences classified in the gastrointestinal (diarrhoea, nausea, vomiting), nervous system-related (dizziness, sensory-related), and psychiatric (irritability, depression-related) organ systems were numerically higher or statistically significantly higher in all taranabant groups compared with the placebo group.

CONCLUSIONS

After 36 and 52 weeks, treatment with taranabant at the 1- and 2-mg doses led to clinically significant weight loss and improvement in glycaemic parameters in overweight and obese patients with T2DM that was associated with dose-related increases in adverse experiences. Based on these data and data from other Phase III clinical studies, it was determined that the overall safety and efficacy profile of taranabant did not support further development for the treatment of obesity.

A clinical trial assessing the safety and efficacy of the CB1R inverse agonist taranabant in obese and overweight patients: low-dose study

OBJECTIVE

To evaluate the weight loss efficacy, safety and tolerability of taranabant, a CB1R inverse agonist, in obese and overweight patients.

DESIGN

Multicenter, double-blind, randomized, placebo-controlled study.

SUBJECTS

Patients >or=18 years old, BMI 27-43 kg m(-2), were randomized to placebo (n=209) or taranabant 0.5 mg (n=207), 1 mg (n=208) or 2 mg given orally once daily (n=417) for 52 weeks.

MEASUREMENTS

Key efficacy measurements included body weight (BW), waist circumference (WC), lipid endpoints and glycemic endpoints.

RESULTS

Based on a last observation carried forward analysis of the all-patients-treated population, mean change in BW for taranabant 0.5, 1, and 2 mg and placebo was -5.4, -5.3, -6.7 and -1.7 kg, respectively (P<0.001 for all doses vs placebo). The proportions of patients who lost at least 5 and 10% of their baseline BW at week 52 were significantly higher for all taranabant doses vs placebo (P<0.001 for all doses). Reductions in WC, percentage of body fat, and triglycerides were significant for taranabant 2 mg and in triglycerides for taranabant 1 mg vs placebo. There was no effect of taranabant vs placebo on other lipid or glucose-related endpoints. Incidences of adverse experiences classified in the gastrointestinal (diarrhea and nausea), nervous system (dizziness/dizziness postural), psychiatric-related (irritability and anger/aggression) and vascular (flushing/hot flush) organ systems were higher and statistically significant in the taranabant 2-mg group compared with the placebo group. Irritability was higher and statistically significant in all taranabant groups compared with the placebo group.

CONCLUSION

All three doses of taranabant-induced clinically meaningful and statistically significant weight loss. Incidences of adverse experiences in organ systems known to express CB1R were higher in taranabant groups.

Elderly Mexicans have less muscle and greater total and truncal fat compared to African-Americans and Caucasians with the same BMI

BACKGROUND

How body composition, specifically skeletal muscle mass, compares in Mexican elderly to other ethnic groups has not previously been reported. We tested the hypothesis that older adults from Northwest Mexico (Mex) would have similar total appendicular skeletal muscle (TASM) compared with New York dwelling Caucasians (Cauc) and African-Americans (AA).

METHODS

Two hundred and eighty nine Mex (135 males and 154 females), 166 AA (36 males and 130 females) and 229 Cauc (64 males and 165 females), aged 60-98 years were assessed. Total and regional fat and lean tissues were measured by whole-body dual energy X-ray absorptiometry where TASM is the sum of arm and leg bone-free and fat-free lean tissue. Differences in TASM were tested by ANCOVA, with age, height, and body mass index (BMI) as covariates.

RESULTS

TASM adjusted for ethnicity, age, height and BMI, were 22.6 +/- 0.2 kg and 17.8 +/- 0.1 kg for males and females, respectively (p < 0.001). Among males with similar age, height, and BMI, Mex had less TASM compared with AA and Cauc (p < 0.001). Total body fat and truncal fat were higher (p < 0.001) and FFM lower (p < 0.001) in Mex compared to both AA and Cauc males after adjusting for age and BMI. Among females, Mex had higher total and truncal fat (p < 0.001) after adjusting for age and BMI, and significantly lower TASM (p < 0.001) after adjusting for age, height, and BMI compared to AA and Cauc females.

CONCLUSIONS

Elderly Mex have a different body composition compared with AA and Cauc of a similar BMI and age. Mex have significantly less TASM with greater total and truncal fat. In the long-term, Mex elderly may be at greater risk for sarcopenic obesity compared to other ethnic groups.

Body mass index as a phenotypic expression of adiposity: quantitative contribution of muscularity in a population-based sample

OBJECTIVE

Although widely applied as a phenotypic expression of adiposity in population and gene-search studies, body mass index (BMI) is also acknowledged to reflect muscularity even though relevant studies directly measuring skeletal muscle (SM) mass are lacking. The current study aimed to fill this important gap by applying advanced imaging methods to test the hypothesis that, after controlling first for adiposity, SM mass is also a significant determinant of BMI in a population-based sample.

DESIGN

Whole-body magnetic resonance imaging scans were completed in Coronary Artery Risk Development in Young Adults study subjects aged 33-45 years. Physical activity (PA) levels, alcohol intake and adequacy of food intake were assessed by standardized questionnaires.

SUBJECTS

The study included 58 African-American (AA) and 78 Caucasian (C) men; and 63 AA and 64 C women.

MEASUREMENTS

Whole-body adipose tissue (AT) and SM volumes.

RESULTS

AT was significantly predicted by not only BMI, but also PA and alcohol intake with total model R (2)'s of 0.68 (P<0.0001) for men and 0.89 (P<0.0001) for women. Men had more SM than AT at all levels of BMI whereas SM predominated in women at lower BMIs (C<26 kg/m(2); AA<28 kg/m(2)). In men, both AT and SM contributed a similar proportion of between-subject variation in BMI. In contrast, in women AT contributed approximately 30% more than SM to the variation in BMI. Developed allometric models indicated SM associations with AT, PA and race after adjusting for height. There was little association of age, lifestyle factors or race with BMI after controlling for both AT and SM.

CONCLUSION

Variation in muscularity provides a mechanistic basis for the previously observed nonspecificity of BMI as a phenotypic expression of adiposity. These quantitative observations have important implications when choosing adiposity measures in population and gene-search studies.

Resting energy expenditure in white and non-white severely obese women

This study aimed to compare the resting energy expenditure (REE) of white and non-white severely obese Brazilian women. REE was examined in 83 severely obese Brazilian women (n = 58 white and 25 non-white) with mean (+/- SD) age 42.99 +/- 11.35 and body mass index 46.88 +/- 6.22 kg/m(2) who were candidates for gastric bypass surgery. Body composition was assessed by air displacement plethysmography (ADP) BOD PODO body composition system (Life Measurement Instruments, Concord, CA) and REE was measured, under established protocol, with an open-circuit calorimeter (Deltatrac II MBM-200, Datex-Ohmeda, Madison, WI, USA). There was no significant difference between the REE of white and non-white severely obese women (1,953 +/- 273 and 1,906 +/- 271 kcal/d, respectively; p = 0.48). However, when adjusted for fat free mass (MLG), REE was significantly higher in nonwhite severely obese women (difference between groups of 158.4 kcal, p < 0.01). REE in white women was positively and significantly correlated to C-reactive protein (PCR) (r = 0.418; P < 0.001) and MLG (r = 0.771; P < 0.001). In the non-white women, REE was only significantly correlated to MLG (r = 0.753; P < 0.001). The multiple linear regression analysis showed that skin color, MLG and PCR were the significant determinants of REE (R(2) = 0.55). This study showed that, after adjustment for MLG, non-white severely obese women have a higher REE than the white ones. The association of body composition inflammation factors and REE in severely obese Brazilian women remains to be further investigated.

Attrition from randomized controlled trials of pharmacological weight loss agents: a systematic review and analysis

Clinical trials of obesity treatments have been limited by substantial dropout. Participant-level variables do not reliably predict attrition, and study-level variables have not yet been examined. We searched MEDLINE and identified 24 large randomized controlled trials of weight loss medications. These trials were comprised of 23 placebo and 32 drug groups. Two authors independently extracted the following for each treatment group: (i) treatment received; (ii) design characteristics (inclusion of a lead-in period, selection of participants with weight-related comorbidities, study location and number of study visits); (iii) sample characteristics (sample size, % female, and mean baseline age and body mass index); and (iv) attrition (total, adverse event [AE]-related and non-AE-related) at 1 year. The primary outcome was total attrition, which was significantly related to treatment (i.e. 34.9%, 28.6%, 28.3% and 35.1% in placebo, orlistat, sibutramine and rimonabant groups, respectively, P < 0.0001). In adjusted multivariable models, total attrition was significantly lower in groups that completed a pre-randomization lead-in period than in those that did not (29.1% vs. 39.9%, P < 0.01). Gender also was significantly related to total attrition; groups with more women had higher dropout (P < 0.01). The pattern was similar for predicting non-AE-related attrition. Findings suggest ways to design studies that maximize retention.

Assessment of body composition in dialysis patients by arm bioimpedance compared to MRI and 40K measurements

This study used multi-frequency bioimpedance spectroscopy (BIS) of the arm and whole body to estimate muscle mass (MM) and subcutaneous adipose tissue (SAT) in 31 hemodialysis (HD) patients comparing these results with magnetic resonance imaging (MRI) and body potassium ((40)K) as gold standards. Total body and arm MM (MM(MRI)) and SAT (SAT(MRI)) were measured by MRI. All measurements were made before dialysis treatment. Regression models with the arm (aBIS) and whole body (wBIS) resistances were established. Correlations between gold standards and the BIS model were high for the arm SAT (r(2) = 0.93, standard error of estimate (SEE) = 3.6 kg), and whole body SAT (r(2) = 0.92, SEE = 3.5 kg), and for arm MM (r(2) = 0.84, SEE = 2.28 kg) and whole body MM (r(2) = 0.86, SEE = 2.28 kg). Total body MM and SAT can be accurately predicted by arm BIS models with advantages of convenience and portability, and it should be useful to assess nutritional status in HD patients.

Body composition analysis: Cellular level modeling of body component ratios

During the past two decades, a major outgrowth of efforts by our research group at St. Luke's-Roosevelt Hospital is the development of body composition models that include cellular level models, models based on body component ratios, total body potassium models, multi-component models, and resting energy expenditure-body composition models. This review summarizes these models with emphasis on component ratios that we believe are fundamental to understanding human body composition during growth and development and in response to disease and treatments. In-vivo measurements reveal that in healthy adults some component ratios show minimal variability and are relatively 'stable', for example total body water/fat-free mass and fat-free mass density. These ratios can be effectively applied for developing body composition methods. In contrast, other ratios, such as total body potassium/fat-free mass, are highly variable in vivo and therefore are less useful for developing body composition models. In order to understand the mechanisms governing the variability of these component ratios, we have developed eight cellular level ratio models and from them we derived simplified models that share as a major determining factor the ratio of extracellular to intracellular water ratio (E/I). The E/I value varies widely among adults. Model analysis reveals that the magnitude and variability of each body component ratio can be predicted by correlating the cellular level model with the E/I value. Our approach thus provides new insights into and improved understanding of body composition ratios in adults.

MRI-measured bone marrow adipose tissue is inversely related to DXA-measured bone mineral in Caucasian women

INTRODUCTION

Recent studies suggest that bone marrow adipose tissue (BMAT) might play a role in the pathogenesis of osteoporosis. Previous research using regional magnetic resonance spectroscopy methods to measure BMAT has reported inconsistent findings on the relationship between BMAT and dual-energy absorptiometry (DXA)-measured bone mineral density (BMD).

METHODS

In the present study, total body and pelvic BMAT were evaluated in 56 healthy women (age 18-88 yrs, mean +/- SD, 47.4 +/- 17.6 yrs; BMI, 24.3 +/- 4.2 kg/m(2)) with T1-weighted whole-body magnetic resonance imaging (MRI). BMD was measured using the whole-body DXA mode (GE Lunar DPX, software version 4.7).

RESULTS

A strong negative correlation was observed between pelvic BMAT and BMD (total-body BMD, R = -0.743, P < 0.001; pelvic BMD, R = -0.646, P < 0.001), and between total-body BMAT and BMD (total-body BMD, R = -0.443, P < 0.001; pelvic BMD, R = -0.308, P < 0.001). The inverse association between pelvic BMAT and BMD remained strong after adjusting for age, weight, total body fat, and menopausal status (partial correlation: total-body BMD, R = -0.553, P < 0.001; pelvic BMD, R = -0.513, P < 0.001). BMAT was also highly correlated with age (pelvic BMAT, R = 0.715, P < 0.001; total-body BMAT, R = 0.519, P < 0.001).

CONCLUSION

MRI-measured BMAT is thus strongly inversely correlated with DXA-measured BMD independent of other predictor variables. These observations, in the context of DXA technical concerns, support the growing evidence linking BMAT with low bone density.

Truncal fat in relation to total body fat: influences of age, sex, ethnicity and fatness

OBJECTIVE

To investigate the influence of age, sex, ethnicity and total fatness on central obesity in four ethnic populations.

DESIGN

Cross-sectional analysis of study subjects enrolled from 1993 to 2005.

SUBJECTS

A multi-ethnic (Caucasian (CA), African-American (AA), Hispanic-American (HA) and Asian (As)) convenience sample of 604 men and 1192 women (aged 18-96 years, body mass index 15.93-45.80 kg/m(2)).

MEASUREMENTS

Total body fat (TBF) and truncal fat were measured by dual-energy X-ray absorptiometry. General linear regression models were used to test for independent associations with log(10)-transformed truncal fat.

RESULTS

For all ethnicities, men had a lower percent body fat and more truncal fat than women. Log(10-)transformed truncal fat increased with TBF approximately as a square root function. At older ages, there was a greater amount of truncal fat in CA, HA and As men (approximately 0.20-0.25 kg/decade) with the effect more pronounced in AA men ( approximately 0.33 kg/decade). For women, the increment of truncal fat per decade was reduced in CA and AA women (approximately 0.07 kg) compared with As and HA women (approximately 0.33 kg). Adjusted for mean values of covariates in our sample, AA had less truncal fat than As.

CONCLUSION

The accumulation of truncal fat is strongly related to age, ethnicity and total fatness in both men and women.

Metabolic consequences of body size and body composition in hemodialysis patients

Small body mass index is associated with increased mortality in chronic hemodialysis patients. The reasons for this observation are unclear but may be related to body composition. This study aimed to investigate the body composition in chronic hemodialysis patients. The difference between body mass and the sum of muscle, bone, subcutaneous, and visceral adipose tissue masses, measured by whole body magnetic resonance imaging, was defined as the high metabolic rate compartment representing the visceral mass. Protein catabolic rate was calculated from urea kinetics. Forty chronic hemodialysis patients (mean age 54.7 years; 87.5% African Americans; 45% females) were studied. High metabolic rate compartment expressed in percent of body weight was inversely related to body weight (r=-0.475; P=0.002) and body mass index (r=-0.530; P<0.001). In a multiple linear regression model, protein catabolic rate was significantly correlated only with high metabolic rate compartment (r=0.616; P<0.001). Assuming that protein catabolic rate in addition to protein intake reflects urea and uremic toxin generation, it follows that high metabolic rate compartment is the major compartment involved in their generation. Consequently, uremic toxin production rate may be relatively higher in patients with low body weight and low body mass index as compared to their heavier counterparts. The poorer survival observed in smaller dialysis patients may be related to these relative differences.

How much may I eat? Calorie estimates based upon energy expenditure prediction equations

How much may I eat? Most healthcare workers, when asked this question, have insufficient knowledge to educate their patients on a healthy energy intake level. In this review we examine the available methods for estimating adult energy requirements with a focus on the newly developed National Academy of Sciences/Institute of Medicine (NAS/IOM) doubly-labelled water total energy expenditure (TEE) prediction equations. An overview is first provided of the traditional factorial method of estimating energy requirements. We then extend this overview by exploring the development of the NAS/IOM TEE prediction models and their role in estimating energy requirements as a function of sex, age, weight, height and physical activity level. The NAS/IOM prediction models were developed for evaluating group energy requirements, although the formulas can be applied in individual 'example' patients for educational purposes. Potential limitations and interpretation issues of both the factorial and NAS/IOM methods are examined. This information should provide healthcare professionals with the tools and understanding to appropriately answer the question, 'How much may I eat?'

Visceral adipose tissue: relationships between single slice areas at different locations and obesity-related health risks

BACKGROUND

Visceral adipose tissue (VAT) is widely recognized as conveying the highest health risk in humans among the currently measurable adipose tissue compartments. A recent study indicated that the traditionally measured VAT area at L(4)-L(5) is not the VAT area with the highest correlation with total VAT volume. At present, it is unknown whether the area with the highest correlation is also the most strongly associated with obesity-related health risk.

OBJECTIVE

The study aim was to establish which VAT slice area(s) are most strongly associated with obesity-related health risk indicators.

DESIGN

The subjects were a convenience sample of healthy adults who completed whole-body magnetic resonance imaging (MRI) scans. The correlations, with appropriate adjustments, were examined between individual MRI slice VAT areas and fasting serum/plasma triglycerides (TG), high-density lipoprotein cholesterol (HDL), glucose, insulin and blood pressure.

RESULTS

The sample consisted of 283 healthy men (age (mean+/-s.d.) 41.9+/-15.8 years; BMI, 26.0+/-3.2 kg/m(2); VAT, 2.7+/-1.8 L) and 411 women (age, 48.1+/-18.7 years; BMI 27.0+/-5.4 kg/m(2); VAT, 1.7+/-1.2 L). After adjusting for age, race, menopause status, scan position and specific blood analysis laboratory, VAT area at L(4)-L(5) had lower correlations with most metabolic risk factors including serum/plasma TG, HDL, glucose, insulin and blood pressure than VAT volume in both men and women. The VAT areas 10 and 15 cm above L(4)-L(5) in men had higher or equal correlations with health risk measures than VAT volume. In women, the VAT area 5 cm above or below L(4)-L(5) and total VAT volume had similar correlations with health risk measures.

CONCLUSIONS

An appropriately selected single slice VAT area is an equally reliable phenotypic marker of obesity-related health risk as total VAT volume. However, in both men and women the VAT slice area at the traditional L(4)-L(5) level is not the best marker of obesity-related health risk.

Measuring partial body potassium in the arm versus total body potassium

Skeletal muscle (SM), the body's main structural support, has been implicated in metabolic, physiological, and disease processes in humans. Despite being the largest tissue in the human body, its assessment remains difficult and indirect. However, being metabolically active it contains over 50% of the total body potassium (TBK) pool. We present our preliminary results from a new system for measuring partial body K (PBK) that presently are limited to the arm yet provide a direct and specific measure of the SM. This uniquely specific quantification of the SM mass in the arm, which is shielded from the body during measurement, allows us to simplify the assumptions used in deriving the total SM, thereby possibly improving the modeling of the human body compartments. Preliminary results show that PBK measurements are consistent with those from the TBK previously obtained from the same subjects, thus offering a simpler alternative to computed tomography and magnetic resonance imaging used for the same purposes. The PBK system, which can be set up in a physician's office or bedside in a hospital, is completely passive, safe, and inexpensive; it can be used on immobilized patients, children, pregnant women, or other at-risk populations.

Treatment of Parkinson disease with diet-induced hyperketonemia: a feasibility study

Ketones may bypass the defect in complex I activity implicated in Parkinson disease (PD). Five of seven volunteers with PD were able to prepare a "hyperketogenic" diet at home and adhere to it for 28 days. Substituting unsaturated for saturated fats appeared to prevent cholesterol increases in four volunteers. Unified Parkinson's Disease Rating Scale scores improved in all five during hyperketonemia, but a placebo effect was not ruled out.

New bioimpedance analysis system: improved phenotyping with whole-body analysis

OBJECTIVE

Bioimpedance analysis (BIA) is a potential field and clinical method for evaluating skeletal muscle mass (SM) and %fat. A new BIA system has 8-(two on each hand and foot) rather than 4-contact electrodes allowing for rapid 'whole-body' and regional body composition evaluation.

DESIGN

This study evaluated the 50 kHz BC-418 8-contact electrode and TBF-310 4-contact electrode foot-foot BIA systems (Tanita Corp., Tokyo, Japan).

SUBJECTS

There were 40 subject evaluations in males (n=20) and females (n=20) ranging in age from 6 to 64 y. BIA was evaluated in each subject and compared to reference lean soft-tissue (LST) and %fat estimates in the appendages and remainder (trunk+head) provided by dual-energy X-ray absorptiometry (DXA). Appendicular LST (ALST) estimates from both BIA and DXA were used to derive total body SM mass.

RESULTS

The highest correlation between total body LST by DXA and impedance index (Ht(2)/Z) by BC-418 was for the foot-hand segments (r=0.986; left side only) compared to the arm (r=0.970-0.979) and leg segments (r=0.942-0.957)(all P<0.001). The within- and between-day coefficient of variation for %fat and ALST evaluated in five subjects was <1% and approximately 1-3.7%, respectively. The correlations between 8-electrode predicted and DXA appendicular (arms, legs, total) and trunk+head LST were strong and highly significant (all r> or =0.95, P<0.001) and group means did not differ across methods. Skeletal muscle mass calculated (Kim equation) from total ALST by DXA (X+/-s.d.)(23.7+/-9.7 kg) was not significantly different and highly correlated with BC-418 estimates (25.2+/-9.6 kg; r=0.96, P<0.001). There was a good correlation between total body %fat by 8-electrode BIA vs DXA (r=0.87, P<0.001) that exceeded the corresponding association with 4-electrode BIA (r=0.82, P<0.001). Group mean segmental %fat estimates from BC-418 did not differ significantly from corresponding DXA estimates. No between-method bias was detected in the whole body, ALST, and skeletal muscle analyses.

CONCLUSIONS

The new 8-electrode BIA system offers an important new opportunity of evaluating SM in research and clinical settings. The additional electrodes of the new BIA system also improve the association with DXA %fat estimates over those provided by the conventional foot-foot BIA.

Low physical activity levels of modern Homo sapiens among free-ranging mammals

Obesity prevalence rates are increasing worldwide and one prevailing hypothesis is that physical activity levels of modern humans are markedly reduced compared to those of our Paleolithic ancestors. We examine this hypothesis by deriving relative activity energy expenditure from available doubly labeled water and indirect calorimetry data in free-ranging non-human mammals. Our results, given the constraints posed by limited data availability, suggest that a low physical activity level, much less than that observed in free-ranging non-human mammals or highly active humans, is present in modern adult humans living within advanced settings. Our observations lend support to the hypothesis that low activity-related energy expenditure levels contribute to the rising worldwide prevalence of obesity.

Added thermogenic and satiety effects of a mixed nutrient vs a sugar-only beverage

OBJECTIVE

To examine the effects of a sugar-only (SO) beverage vs one containing a mixed-nutrient (MN) composition on energy expenditure and feelings of hunger and satiety.

HYPOTHESIS

A beverage containing a mixed macronutrient composition will lead to greater thermic effect of food and feelings of fullness than an isocaloric beverage containing only sugar.

RESEARCH METHODS AND PROCEDURES

Adults were randomly assigned to receive a 2510 kJ (600 kcal) SO liquid formula followed by an isovolumic, isoenergetic, MN liquid formula with an energy distribution of 17% protein, 67% carbohydrates as sucrose and corn syrup solids, and 16% fat, or vice versa, in a crossover design. The carbohydrate source in the two beverages was identical: 1:1 ratio of sucrose and corn syrup solids (25 dextrose equivalents). The thermic response was calculated as the 7 h deviation from resting metabolic rate (RMR). Subjects provided hunger/satiety ratings and other related information by visual analog scales at regular intervals throughout the study period.

RESULTS

In all, 20 subjects completed the protocol; one was removed from the thermic effect analysis due to discrepant RMRs. Following beverage ingestion, SO and MN liquid meals produced 7 h thermic effects of (X+/-s.e.m.) 274.1+/-27.6 kJ (65.5+/-6.6 kcal) and 372.0+/-33.9 kJ (88.9+/-8.1 kcal), respectively, resulting in a significant (P<0.01) difference between meals (Delta=97.9+/-35.1 kJ [23.4+/-8.4 kcal]). Analysis of satiety ratings using area under the curve analysis showed greater feelings of satiety (P<0.05) with MN compared to SO consumption. Also, subjects felt that they could eat less (P<0.05) after consumption of the MN vs SO beverage.

DISCUSSION

In comparison to MN beverages, SO beverages are associated with a relatively high-energy retention without accompanying subjective hunger/fullness compensations, suggesting a basis for their role in long-term unintentional weight gain in healthy adults.

Proof-of-Principle to Measure Potassium in the Human Brain: A Feasibility Study

We describe the results of a proof-of-principle to measure the potassium content in the human brain using the natural radioisotope (40)K that is in equilibrium with the stable isotopes of potassium, (39)K and (41)K. A fixed relationship exists between radioactive potassium and the total potassium in the brain, which in turn reflects the brain's cell mass and intracellular water compartment. Accordingly, we explored whether measurements of brain potassium could serve as possible indicators of intracellular cerebral edema. We designed, built, and then calibrated our system using a spherical phantom containing KCl salt dissolved in water at levels comparable to those in the human brain. Emitted radiation was detected using sodium iodide (Nal) and high-purity germanium (HP-Ge) detectors. Our results with phantoms and with five volunteers demonstrate the feasibility of measuring potassium at the levels normally present in human brain tissue. We plan to extend the system to detect the onset of brain edema in patients with multiple sclerosis.

Measurement of intramyocellular lipid levels with 2-D magnetic resonance spectroscopic imaging at 1.5 T

Intramyocellular lipid (IMCL) plays an important role in the study of metabolism in vivo. Magnetic resonance spectroscopy (MRS) studies of IMCL are usually performed with clinical 1.5-T magnetic resonance imaging (MRI) systems and have employed the single-voxel MRS technique. The present study reports the results of our systematic evaluation of the ability of single- and multi-voxel MRS to yield high-quality, contamination-free IMCL levels from the tibialis anterior (TA) muscle. A clinical, 1.5-T, whole-body MRI scanner was used to measure IMCL with a standard knee coil, head coil, or a 3-cm receive-only surface coil with a body coil transmit. Excellent IMCL spectra were obtained in healthy males in only 8 min from multiple 0.25-cm(3) voxels using the surface coil receive/body coil transmit in conjunction with the standard PRESS spectroscopic imaging (SI) technique. This approach provided the spatial resolution and voxel placement flexibility permitting optimal separation of IMCL and extramyocellular lipid. Our findings demonstrate the potential of the SI approach.