Skeletal differences between black and white men and their relevance to body composition estimates

Worldwide Anatomic Characteristics of the Mandibular Canine-A Multicenter Cross-Sectional Study with Meta-Analysis

INTRODUCTION

This study aimed to examine the global prevalence of root and root canal morphologies in mandibular canines and analyze potential influences of region, ethnicity, sex, and age on the proportion of a second root and root canal configuration.

METHODS

Observers from 44 countries screened 13,200 canines using cone-beam computed tomographic exams and gathered data on the percentages of 2 root canal morphologies and 2-rooted configurations (primary outcomes), as well as the root canal configurations (secondary outcome). Demographic factors (ethnicity, sex, and age) were collected for each participant. Primary outcomes were represented as odds ratios and untransformed proportions accompanied by 95% confidence interval (CI) forest plots. Meta-analysis compared subgroups and identified sources of heterogeneity. Intra- and inter-rater tests were conducted. Statistical significance was set at 5%.

RESULTS

The worldwide prevalence of a second canal was 7.5% (95% CI, 6.3%-8.7%), ranging from 0.7% in Nigeria to 17.7% in Uruguay. The meta-analysis also revealed significant variations when comparing ethnicity, gender, and age (P < .05). The global prevalence of a second root was 1.9% (95% CI, 1.5%-2.3%), with the highest proportion observed in Spain (6.7%). Caucasian and Indian (south Asian) ethnic groups, females, and older patients exhibited higher proportions of 2 roots (P < .05). Meta-regression excluded side, voxel size, and field of view as sources of heterogeneity (P > .05).

CONCLUSIONS

The prevalence of 2 root canals and 2-rooted configurations in the mandibular canine exhibited variations based on geographic location, ethnicity, sex, and age. The global prevalence of 2 root canals and 2-root configuration was 7.5% and 1.9%, respectively.

Development and validation of a rapid multicompartment body composition model using 3-dimensional optical imaging and bioelectrical impedance analysis

BACKGROUND & AIMS

The multicompartment approach to body composition modeling provides a more precise quantification of body compartments in healthy and clinical populations. We sought to develop and validate a simplified and accessible multicompartment body composition model using 3-dimensional optical (3DO) imaging and bioelectrical impedance analysis (BIA).

METHODS

Samples of adults and collegiate-aged student-athletes were recruited for model calibration. For the criterion multicompartment model (Wang-5C), participants received measures of scale weight, body volume (BV) via air displacement, total body water (TBW) via deuterium dilution, and bone mineral content (BMC) via dual energy x-ray absorptiometry. The candidate model (3DO-5C) used stepwise linear regression to derive surrogate measures of BV using 3DO, TBW using BIA, and BMC using demographics. Test-retest precision of the candidate model was assessed via root mean square error (RMSE). The 3DO-5C model was compared to criterion via mean difference, concordance correlation coefficient (CCC), and Bland-Altman analysis. This model was then validated using a separate dataset of 20 adults.

RESULTS

67 (31 female) participants were used to build the 3DO-5C model. Fat-free mass (FFM) estimates from Wang-5C (60.1 ± 13.4 kg) and 3DO-5C (60.3 ± 13.4 kg) showed no significant mean difference (-0.2 ± 2.0 kg; 95 % limits of agreement [LOA] -4.3 to +3.8) and the CCC was 0.99 with a similar effect in fat mass that reflected the difference in FFM measures. In the validation dataset, the 3DO-5C model showed no significant mean difference (0.0 ± 2.5 kg; 95 % LOA -3.6 to +3.7) for FFM with almost perfect equivalence (CCC = 0.99) compared to the criterion Wang-5C. Test-retest precision (RMSE = 0.73 kg FFM) supports the use of this model for more frequent testing in order to monitor body composition change over time.

CONCLUSIONS

Body composition estimates provided by the 3DO-5C model are precise and accurate to criterion methods when correcting for field calibrations. The 3DO-5C approach offers a rapid, cost-effective, and accessible method of body composition assessment that can be used broadly to guide nutrition and exercise recommendations in athletic settings and clinical practice.

Worldwide Assessment of the Root and Root Canal Characteristics of Maxillary Premolars - A Multi-center Cone-beam Computed Tomography Cross-sectional Study With Meta-analysis

INTRODUCTION

This worldwide study examined the root and root canal characteristics of maxillary premolars and explored how demographic factors impact the outcomes.

METHODS

Observers from 44 countries assessed 26,400 maxillary premolars using cone-beam computed tomography and employed a standardized screening method to gather data on multiple canal morphology and 3-rooted configuration (primary outcomes), as well as secondary outcomes related to root and root canal anatomies. Demographic factors such as ethnicity, sex, and age were collected for each participant. The intra- and inter-observer tests ensured observer reliability. Primary outcomes were represented as odds ratios and untransformed proportions accompanied by 95% confidence interval (CI) forest plots. Meta-analysis compared sub-groups and identified sources of heterogeneity (α = 5%).

RESULTS

The overall prevalence of multiple canal morphology in the first premolar was 93.5% (95% CI, 93.3%-94.7%), while in the second premolar, it was 49.7% (95% CI, 44.9%-54.6%). The proportion of 3-rooted configuration was 1.8% (95% CI, 1.4%-2.1%) in the first premolar and 0.4% (95% CI, 0.3%-0.5%) in the second. Asian countries generally displayed fewer roots and root canals, while European nations showed higher counts (P < .05). Males exhibited higher percentages and odds ratios for both outcomes in both premolars. Younger patients demonstrated lower percentages of multiple root canal morphologies (P < .05). Factors such as tooth side, voxel size and field-of-view did not influence the outcomes (P > .05).

CONCLUSIONS

The worldwide assessment of root and root canal characteristics of maxillary premolars has revealed a discernible influence of various factors such as tooth type, geographical region, ethnicity, sex, and age.

Worldwide Prevalence of the Lingual Canal in Mandibular Incisors - A Multi-Center Cross-Sectional Study with Meta-Analysis

INTRODUCTION

This cross-sectional study assessed the influence of patient demographics on the worldwide prevalence of a lingual canal in mandibular incisors.

METHODS

26,400 mandibular incisors were evaluated using cone-beam computed tomography imaging by pre-calibrated observers from 44 countries. A standardized screening method was employed to collect data on the presence of a lingual canal, the anatomic configuration of the root canal, and number of roots. Patient demographic information (age, sex, and ethnicity) was also recorded. Multiple intra- and inter-rater tests assessed the reliability of the observers and groups, and a meta-analysis was used to examine differences and heterogeneities (α=5%).

RESULTS

The prevalence of the lingual canal in mandibular central and lateral incisors varied from 2.3% (0.06%-4.0%; Nigeria) to 45.3% (39.7%-51.0%; Syria) and from 2.3% (0.06%-4.0%; Nigeria) to 55.0% (49.4%-60.6%; India), respectively. Ethnicity had a significant impact on the prevalence of the lingual canal, with African, Asian, and Hispanic groups having the lowest proportions (P<.05), while Caucasians, Indians, and Arabs showed the highest (P<.05) for both incisor groups. Additionally, males had a significantly higher odds ratio for both the central (1.334) and lateral (1.178) incisors, while older patients had a lower prevalence for both tooth groups (P<.05). The side and tooth group did not influenced on the outcomes.

CONCLUSIONS

The prevalence of lingual root canals in mandibular incisors varies significantly based on geographic location, ethnicity, age, and gender. The overall prevalence was 21.9% for mandibular central incisors and 26.0% for lateral incisors.

Utility of a Score for Predicting Glomerular Filtration Rate Overestimation in Patients with Cardiovascular and Renal Diseases and Their Risk Factors

Objective We recently reported a novel score for the detection of glomerular filtration rate (GFR) overestimation using a creatinine-based equation. We examined the utility of this score in patients with cardiovascular/renal diseases and diabetes mellitus. Methods We enrolled 1,425 patients (65±15 years old; 37% women) who were admitted to our hospital for the management of cardiovascular and renal diseases and their risk factors. Overestimation of the GFR (OE) was defined as a creatinine-based GFR (eGFRcre) ≥120% of the cystatin C-based estimated GFR. The OE score was calculated as the sum of the scores for the body weight, hemoglobin concentration, and blood urea nitrogen (BUN)/serum creatinine (Scr), totaling 1 point if the body weight was <63.0 kg in men or <42.0 kg in women, 1 point if the hemoglobin concentration was <12.4 g/dL in men or <11.0 g/dL in women, and 1 point if the BUN/Scr was >26.5. Results The proportion of patients with OE was 14.2%. The score predicted OE with a sensitivity of 70.8% and a specificity of 99.6%, and the sensitivity was increased in patients ≥75 years old (88.3%) and decreased in diabetics (58.6%). When patients were divided into subgroups by the total score, the frequencies of OE were 8% (59/754), 14% (72/502), 38% (58/151), and 72% (13/18) in patients with scores of 0, 1, 2, and 3, respectively. Conclusion The OE score is useful for detecting elderly cases of cardiovascular and renal diseases in which eGFRcre overestimates the GFR, although its utility is limited in diabetics.

High percent body fat mass predicts lower risk of cardiac events in patients with heart failure: an explanation of the obesity paradox

Background

Although high body mass index (BMI) is a risk factor of heart failure (HF), HF patients with a higher BMI had a lower mortality rate than that in HF patients with normal or lower BMI, a phenomenon that has been termed the “obesity paradox”. However, the relationship between body composition, i.e., fat or muscle mass, and clinical outcome in HF remains unclear.

Methods

We retrospectively analyzed data for 198 consecutive HF patients (76 years of age; males, 49%). Patients who were admitted to our institute for diagnosis and management of HF and received a dual-energy X-ray absorptiometry scan were included regardless of left ventricular ejection fraction (LVEF) categories. Muscle wasting was defined as appendicular skeletal muscle mass index < 7.0 kg/m² in males and < 5.4 kg/m² in females. Increased percent body fat mass (increased FM) was defined as percent body fat > 25% in males and > 30% in females.

Results

The median age of the patients was 76 years (interquartile range [IQR], 67–82 years) and 49% of them were male. The median LVEF was 47% (IQR, 33–63%) and 33% of the patients had heart failure with reduced ejection fraction. Increased FM and muscle wasting were observed in 58 and 67% of the enrolled patients, respectively. During a 180-day follow-up period, 32 patients (16%) had cardiac events defined as cardiac death or readmission by worsening HF or arrhythmia. Kaplan-Meier survival curves showed that patients with increased FM had a lower cardiac event rate than did patients without increased FM (11.4% vs. 22.6%, p = 0.03). Kaplan-Meier curves of cardiac event rates did not differ between patients with and those without muscle wasting (16.5% vs. 15.4%, p = 0.93). In multivariate Cox regression analyses, increased FM was independently associated with lower cardiac event rates (hazard ratio: 0.45, 95% confidence interval: 0.22–0.93) after adjustment for age, sex, diabetes, muscle wasting, and renal function.

Conclusions

High percent body fat mass is associated with lower risk of short-term cardiac events in HF patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-020-01950-9.

Examining Race-Related Error in Two-Compartment Models of Body Composition Assessment: A Systematic Review and Meta-Analysis

BACKGROUND

The Brozek and Siri formulas estimate relative adiposity (%Fat) from total body density (D_b) using a 2-compartment (2C) model. Racial/ethnic differences in D_b have been reported, along with subsequent errors in estimated %Fat.

OBJECTIVE

The primary aim of this systematic review and meta-analysis was to examine potential race/ethnic differences in the accuracy of the Brozek and Siri 2C formulas using aggregate-level data.

METHODS

Peer-reviewed studies available in English that provided 2C and 4C estimates of %Fat were located using searches of the PubMed (n = 150), Scopus (n = 170), and Web of Science (n = 138) online electronic databases. Random-effects models were used to determine potential differences between racial groups using a mean ES and 95% confidence intervals.

RESULTS

The cumulative results from 78 effects indicate that the relative accuracy of the Brozek equation did not vary between racial groups (between group p = 0.053). In contrast, the Siri equation slightly underestimated %Fat for Asian adults (ES_WMD = -1.40%, 95%CI -2.33% to -0.46%; p = 0.004) and Black adults (ES_WMD = -1.10%, 95%CI -2.11% to -0.08%; p = 0.034), with no significant differences observed in Hispanic adults (ES_WMD = 0.64%, 95%CI -1.02% to 2.31%; p = 0.448) and White adults (ES_WMD = 0.08%, 95%CI -0.42% to 0.57%; p = 0.766) (between group p = 0.019).

CONCLUSION

Small, but statistically significant, error was found between racial groups when estimating %Fat using the 2C Siri equation when compared to 4C models. However, the observed error due to race/ethnicity appears to be of little clinical or practical significance when using either equation.

Distinct determinants of muscle wasting in nonobese heart failure patients with and without type 2 diabetes mellitus

BACKGROUND

Muscle wasting, that is, reduction in muscle mass, is frequently observed in patients with chronic heart failure (CHF) and diabetes mellitus (DM).

METHODS

We retrospectively examined 185 patients with CHF (median age of 71 years [interquartile range, 61-78 years]; 64% male) who received a dual-energy X-ray absorptiometry scan for assessment of appendicular skeletal muscle mass index (ASMI).

RESULTS

Seventy patients with CHF (38%) had DM. Patients with DM had higher prevalences of ischemic heart disease and hypertension, lower levels of estimated glomerular filtration rate (eGFR) and ASMI, and higher levels of plasma renin activity (PRA) than did patients without DM. In simple regression analyses, ASMI was positively correlated with the Mini Nutritional Assessment Short Form (MNA-SF) score and levels of hemoglobin, eGFR, and fasting plasma insulin and was negatively correlated with levels of N-terminal pro B-type natriuretic peptide, PRA, and cortisol. In multiple linear regression analyses, age, MNA-SF score, DM, fasting plasma insulin level, and PRA were independently associated with ASMI. When multiple linear regression analyses were separately performed in a non-DM group and a DM group, MNA-SF score and fasting plasma insulin level were independent variables for ASMI in both groups. PRA was independently associated with ASMI in the DM group but not in the non-DM group, whereas cortisol concentration was independently associated with ASMI only in the non-DM group.

CONCLUSIONS

In addition to malnutrition and reduction in plasma insulin, renin-angiotensin system activation may be responsible for the development of muscle wasting in CHF patients with DM.

Sarcopenic Obesity in Facioscapulohumeral Muscular Dystrophy

Background

Sarcopenic obesity has been observed in people with neuromuscular impairment, and is linked to adverse health outcomes. It is unclear, however, if sarcopenic obesity develops in adults with facioscapulohumeral muscular dystrophy (FSHD).

Methods

The purpose of this study was to determine if adults with FSHD meet criteria for sarcopenic obesity (appendicular lean mass index (ALMI) scores of < 7.26 or 5.45 kg/m²; % fat mass (FM) ≥ 28 or 40% in men/women). Ten people with FSHD (50 ± 11 years, 2 females) and ten age/sex-matched controls (47 ± 13 years, 2 females) completed one visit, which included a full-body dual-energy x-ray absorptiometry (DXA) scan. Regional and whole body total mass, fat mass (FM), and lean mass (LM) were collected and body mass index (BMI) and sarcopenia measures were computed.

Results

People with FSHD and controls had a similar whole body total mass (84.5 ± 12.9 vs. 81.8 ± 13.5 kg, respectively, p = 0.65). Though BMI was 2% lower in the FSHD group (p = 0.77), the % FM was 46% higher in FSHD, compared with controls (p < 0.01). In addition, ALM volume was 23% lower (p = 0.02) and ALMI was 27% lower in FSHD compared with controls (p < 0.01). Whole body LM trended to be lower in FSHD vs. controls (p = 0.05), and arm and leg LM were both lower in FSHD compared with controls (p < 0.05). Furthermore, the % LM was 18% lower in FSHD vs. controls (p < 0.01). FSHD participants exhibited greater total body FM (p < 0.01) and total leg FM (p < 0.01), but were similar in volume of total arm FM compared with controls (p = 0.09).

Conclusion

Findings from this study suggest that people with FSHD, although similar in BMI and total body mass compared with controls, commonly meet the definition of sarcopenic obesity. Adults with co-existing FSHD and sarcopenic obesity may be at risk for significant impairments in quality of life, and encounter additional challenges in the management of FSHD manifestations.

Overestimation of glomerular filtration rate by creatinine-based equation in heart failure patients is predicted by a novel scoring system

AIMS

Creatinine-based estimated glomerular filtration rate (eGFRcre) has been shown to overestimate the glomerular filtration rate (GFR) when it is compared with cystatin C-based estimated GFR (eGFRcys) in older people. We investigated clinical determinants of GFR overestimation by eGFRcre and developed a score for prediction of GFR overestimation (OE) in heart failure patients.

METHODS

We retrospectively examined 244 Japanese heart failure patients (aged 72.2 ± 13.1 years; 48% women) who had no known extrarenal factors that affect serum cystatin C concentration. eGFR OE by eGFRcre was defined as eGFRcre being ≥120% of cystatin C-based eGFR.

RESULTS

The proportion of heart failure patients with OE was 14.3%. Patients with OE were older, had lower body weight and total skeletal muscle mass than those in patients without OE. Laboratory examinations showed that hemoglobin concentration was lower, and the ratio of blood urea nitrogen-to-creatinine was higher in patients with OE than in patients without OE. In multivariate regression analysis, body weight (<63.0 kg in men and <42.0 kg in women), hemoglobin level (<12.4 g/dL in men and <11.0 g/dL in women) and ratio of blood urea nitrogen-to-creatinine (>26.5) in addition to skeletal muscle mass were independently associated with OE. A score calculated by using cut-off levels of body weight, hemoglobin concentration and ratio of blood urea nitrogen-to-creatinine predicted OE with a sensitivity of 97.1% and a specificity of 98.1%.

CONCLUSION

Overestimation of GFR by eGFRcre is predictable by a novel scoring system, which might be useful for the detection of patients who require cystatin C-based eGFR measurement for accurate assessment of renal function. Geriatr Gerontol Int 2020; 20: 752-758.

Quantification of muscle mass in the legs of patients with peripheral arterial occlusive disease: associations between volumetric and cross-sectional single-slice measurements for identification of atrophy and focal sarcopenia

BACKGROUND

Sarcopenia, commonly determined by measuring skeletal muscle mass index (SMI) at the third lumbar level, has been identified as a predictor of clinical outcome in a variety of diseases. For patients with peripheral arterial occlusive disease (PAOD), we hypothesized that lower extremity SMI (LESMI) might be a more precise predictor of outcome and the extent of chronic ischemia than the systemic muscle mass at the L3 level. We investigated the association between complete muscle volume and muscle area derived with single-slice 2-dimensional measurements in the legs to identify at which level cross-sectional single-slice measurements are most representative of the muscle volume and investigated whether LESMI is associated with systemic sarcopenia and PAOD severity.

METHODS

Muscle volumes and areas were semiautomatically segmented from computed tomography (CT) scans of the affected and contralateral legs of 50 PAOD patients with Fontaine stage IIb and 50 PAOD patients with Fontaine stage IV. The muscle mass was determined for the complete volumes of the upper and lower legs and for cross-sectional slices at 40%, 50%, and 60% of the length of the femur and tibia. Patients were determined as sarcopenic based on sex-specific cut-off values at the L3 spinal segment. Two observers segmented 20 randomly selected patients to determine the interobserver reliability with the intraclass correlation coefficient.

RESULTS

The correlation between the LESMI of the complete muscle volume and the three cross-sectional slices in all 200 upper and 200 lower legs was moderately strong to strong. Interobserver reliability of cross-sectional slice segmentation was excellent. The LESMI, both measured volumetrically and cross-sectionally, were significantly lower in patients with sarcopenia compared to patients without sarcopenia. The LESMI was lower in patients with Fontaine stage IV compared to patients with Fontaine stage IIb for both volumetric and cross-sectional measurements.

CONCLUSIONS

Segmentation of skeletal muscle mass from cross-sectional single-slice CT in the upper and lower leg can accurately and precisely substitute complete volume segmentations. These findings warrant the use of measurements based on cross-sectional single-slice CT for assessing the LESMI. Patients with systemic sarcopenia are also at increased risk for muscle mass loss in the lower extremities. In the current study, LESMI was lower in patients with Fontaine class IV PAOD compared to patients with Fontaine class IIb PAOD. Future studies should assess the predictive value of the LESMI on clinical outcomes in PAOD patients.

Factors associated with sarcopenia in subjects aged 80 years and over

OBJECTIVE: To analyze whether sarcopenia is associated with sociodemographic factors and chronic noncommunicable diseases in adults aged 80 years and older. METHODS: The sample consisted of 120 adults aged 80 to 95 years (83.4±2.9 years) from the city of Presidente Prudente (São Paulo, Brazil), of which 76 were females (83.4±3.0 years) and 44 were males (83.4±2.6 years). The study sociodemographic and epidemiological factors were: age stratum, gender, marital status, education level, chronic noncommunicable diseases, ethnicity, and nutritional status. Body composition was determined by Dual-Energy X-Ray Absorptiometry and sarcopenia was identified by the appendicular lean mass ratio (upper limb lean mass + lower limb lean mass [kg]/height [m]2). The Chi-square test analyzed whether sarcopenia was associated with sociodemographic and epidemiological factors and binary logistic regression expressed the magnitude of the associations. The data were treated by the software Statistical Package for the Social Sciences (17.0) at a significance level of 5%. RESULTS: The factors associated with sarcopenia were gender, age, nutritional status, and osteopenia/osteoporosis. CONCLUSION: The factors gender, age, nutritional status, and osteopenia/osteoporosis are independently associated with sarcopenia in adults aged 80 years and older.

Skeletal muscle mass indices in healthy young Mexican adults aged 20-40 years: implications for diagnoses of sarcopenia in the elderly population

BACKGROUND AND OBJECTIVES

Skeletal muscle and skeletal muscle indices in young adults from developing countries are sparse. Indices and the corresponding cut-off points can be a reference for diagnoses of sarcopenia. This study assessed skeletal muscle using dual-energy X-ray absorptiometry (DXA) in healthy male and female subjects aged 20-40 years and compared their appendicular skeletal muscle mass (ASM) and total-body skeletal muscle (TBSM) indices using certain cut-off points published in the literature.

METHODS

A sample of 216 healthy adults men and women from northwest Mexico was included. Body composition was assessed by DXA and several published DXA-derived skeletal muscle indices were compared.

RESULTS

Both, ASM and TBSM were higher in men compared to the women group (23.0 ± 3.4 versus 15.9 ± 1.6 kg; P < 0.05 and 26.5 ± 4.1 versus 16.9 ± 1.9 kg; P < 0.05, resp.). These differences were also valid for both indices. When derived cut-off points were compared with the most reported indices, significant differences were found.

INTERPRETATION AND CONCLUSION

Published cut-off points from Caucasians are higher than cut-off point derived in this sample of Mexican subjects. The new DXA-derived cut-off points for ASM proposed herein may improve diagnoses of sarcopenia in the geriatric Mexican population.

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.

Resistance training conserves fat-free mass and resting energy expenditure following weight loss

OBJECTIVE

To determine what effect diet-induced approximately 12 kg weight loss in combination with exercise training has on body composition and resting energy expenditure (REE) in premenopausal African-American (AA) and European-American (EA) women.

METHODS AND PROCEDURES

This study was a longitudinal, randomized weight loss clinical intervention, with either aerobic (AT), resistance (RT), or no exercise training (NT). Forty-eight AA and forty-six EA premenopausal overweight (BMI between 27 and 30) women underwent weight loss to a BMI<25. Body composition (densitometry), REE (indirect calorimetry), maximal oxygen uptake (VO2max), and muscular strength (isometric elbow flexion) were evaluated when subjects were in energy balance.

RESULTS

AA women lost less fat-free mass (FFM, P<or=0.05) (47.0+/-4.6 to 46.9+/-5.0 kg) than EA women (46.4+/-4.9 to 45.2+/-4.6 kg). Regardless of race, RT maintained FFM (P<or=0.05) following weight loss (46.9+/-5.2 to 47.2+/-5.0 kg) whereas AT (45.4+/-4.2 to 44.4+/-4.1 kg) and NT (47.9+/-4.7 to 46.4+/-5.1 kg) decreased FFM (P<or=0.05). Both AT and NT decreased in REE with weight loss but RT did not. Significant time by group interactions (all P<or=0.05) for strength indicated that RT maintained strength and AT did not.

DISCUSSION

AA women lost less FFM than EA women during equivalent weight losses. However, following weight loss in both AA and EA, RT conserved FFM, REE, and strength fitness when compared to women who AT or did not train.

Extracellular water: greater expansion with age in African Americans

Aging is associated with the onset of chronic diseases that lead to pathological expansion of the extracellular water (ECW) compartment. Healthy aging, in the absence of disease, is also reportedly accompanied by a relative expansion of the ECW compartment, although the studies on which this observation is based are few in number, applied different ECW measurement methods, included small ethnically homogeneous subject samples, and failed to adjust ECW for non-age-related influencing factors. The aim of the current study was to examine, in a large (n = 1,538) ethnically diverse [African American (AA), Asian, Caucasian, Hispanic] subject group the cross-sectional relationships between ECW and age after controlling first for other potential factors that may influence fluid distribution. ECW and intracellular water (ICW) were derived from measured total body water (isotope dilution) and potassium (40K whole body counting). The cross-sectional relationships between ECW, ICW, and ECW/ICW (E/I), and age were developed using multiple regression modelling methods. Body weight, weight squared, height, age, sex, race, and interactions were all significant ECW predictors. The slope of the observed race x age interaction was significantly greater in AA (beta = 0.0005, P = 0.005) than in the three other race groups. Race, sex, and age differences in fluid distribution persisted after adjusting for body composition in a subgroup (n = 994) with dual-energy X-ray absorptiometry lean soft tissue and fat measurements. A relative ECW expansion (i.e., E/I) was present with greater age in most sex-race groups, although the effect was not significantly larger in AA males (P > 0.05) compared with the other race groups, except Asians (P < 0.05). For females, a larger E/I-age effect was found in AA compared with the other race groups, but only the comparison against Hispanics was significant (P < 0.05). The ECW compartment and E/I are thus variably larger, according to race, in healthy older subjects independent of sex, lean soft tissue, and fat mass.

Influence of distribution of lean body mass on resting metabolic rate after weight loss and weight regain: comparison of responses in white and black women

BACKGROUND

Little is known about the effect of weight change on regional lean body mass (LBM) distribution or on racial differences in resting metabolic rate (RMR).

OBJECTIVE

The study compared total and regional LBM patterns in white and black women after weight loss and regain and assessed the influence of regional LBM on variances in RMR.

DESIGN

Eighteen white and 22 black women who did not differ in age, weight, and height were studied 3 times: in the overweight state, after weight reduction to the normal-weight state, and after 1 y without intervention. Total and regional lean and fat masses were assessed by dual-energy X-ray absorptiometry.

RESULTS

White and black women did not differ significantly in mean (+/- SD) weight loss (13.4 +/- 3.6 and 12.7 +/- 3.2 kg, respectively) and regain (6.1 +/- 5.5 and 6.4 +/- 5.4 kg, respectively). Black subjects had significantly less trunk LBM and significantly more limb LBM at each time point (P < 0.05). In both races, weight regain was associated with significant increases in limb LBM (P < 0.05) but not in trunk LBM (P = 0.21). RMR, adjusted for total LBM and fat mass, was significantly higher in white women after weight loss (P < 0.01) and regain (P < 0.01). However, no racial difference was found when RMR was adjusted for LBM distribution.

CONCLUSIONS

In both races, trunk LBM decreased with weight loss and remained lower, despite significant weight regain, which potentially reflected decreased organ mass. Regional LBM distribution explained the racial difference in RMR.

Muscularity in adult humans: proportion of adipose tissue-free body mass as skeletal muscle

Muscularity, or the proportion of adipose tissue-free body mass (ATFM) as skeletal muscle (SM), provides valuable body composition information, especially for age-related SM loss (i.e., sarcopenia). Limited data from elderly cadavers suggest a relatively constant SM/ATFM ratio, 0.540 +/- 0.046 for men (mean +/- SD, n = 6) and 0.489 +/- 0.049 for women (n = 7). The aim of the present study was to examine the magnitude and constancy of the SM/ATFM ratio in healthy adults. Whole-body SM and ATFM were measured using multi-scan magnetic resonance imaging. The SM/ATFM ratio was 0.528 +/- 0.036 for men (n = 139) and 0.473 +/- 0.037 for women (n = 165). Multiple regression analysis indicated that the SM/ATFM ratio was significantly influenced by sex, age, body weight, and race. The four factors explained 50% of the observed between individual variation in the SM/ATFM ratio. After adjusting for age, body weight, and race, men had a larger SM/ATFM ratio than women. Both older men and women had a lower SM/ATFM ratio than younger subjects, although the relative reduction was greater in men. After adjustment for sex, age, and body weight, there were no significant differences in the SM/ATFM ratios between Asian, Caucasian, and Hispanic subjects. In contrast, African-American subjects had a significantly greater SM/ATFM ratio than subjects in the other three groups. In addition, the SM/ATFM ratio was significantly lower in AIDS patients than corresponding values in healthy subjects.

Validity of two-component models for estimating body fat of black men

Commonly used two-component model conversion formulas that estimate relative body fat (%BF) from body density (Db) were cross-validated on a heterogeneous sample of black men (n = 30; age = 19--45 yr). A four-component model was used to obtain criterion measures of %BF, and linear regression and analysis of individual residual scores were conducted to assess the predictive accuracy of the formulas under investigation. The two-component formula commonly used to estimate %BF of black men (Schutte JE, Townsend EJ, Hugg J, Shoup RF, Malina RM, and Blomqvist CG. J Appl Physiol 56: 1647-1649, 1984) significantly (P < or = 0.01) and systematically (87% of sample) overestimated %BF (-1.28%); thus we developed the following two-component Db conversion formula: %BF = [(4.858/Db) - 4.394] x 100. Because our formula was derived from a four-component model and a larger, more heterogeneous sample than the commonly used two-component formula, we recommend using it to convert Db to %BF for black men. Additionally, there was good agreement between dual-energy X-ray absorptiometry and the four-component model, making this a suitable alternative for estimating the %BF of black men.

Total-body skeletal muscle mass: development and cross-validation of anthropometric prediction models

BACKGROUND

Skeletal muscle (SM) is a large body compartment of biological importance, but it remains difficult to quantify SM with affordable and practical methods that can be applied in clinical and field settings.

OBJECTIVE

The objective of this study was to develop and cross-validate anthropometric SM mass prediction models in healthy adults.

DESIGN

SM mass, measured by using whole-body multislice magnetic resonance imaging, was set as the dependent variable in prediction models. Independent variables were organized into 2 separate formulas. One formula included mainly limb circumferences and skinfold thicknesses [model 1: height (in m) and skinfold-corrected upperarm, thigh, and calf girths (CAG, CTG, and CCG, respectively; in cm)]. The other formula included mainly body weight (in kg) and height (model 2). The models were developed and cross-validated in nonobese adults [body mass index (in kg/m(2)) < 30].

RESULTS

Two SM (in kg) models for nonobese subjects (n = 244) were developed as follows: SM = Ht x (0.00744 x CAG(2) + 0.00088 x CTG(2) + 0.00441 x CCG(2)) + 2.4 x sex - 0.048 x age + race + 7.8, where R:(2) = 0.91, P: < 0.0001, and SEE = 2.2 kg; sex = 0 for female and 1 for male, race = -2.0 for Asian, 1.1 for African American, and 0 for white and Hispanic, and SM = 0.244 x BW + 7.80 x Ht + 6.6 x sex - 0.098 x age + race - 3.3, where R:(2) = 0.86, P: < 0.0001, and SEE = 2.8 kg; sex = 0 for female and 1 for male, race = -1.2 for Asian, 1.4 for African American, and 0 for white and Hispanic.

CONCLUSION

These 2 anthropometric prediction models, the first developed in vivo by using state-of-the-art body-composition methods, are likely to prove useful in clinical evaluations and field studies of SM mass in nonobese adults.

Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index

BACKGROUND

Although international interest in classifying subject health status according to adiposity is increasing, no accepted published ranges of percentage body fat currently exist. Empirically identified limits, population percentiles, and z scores have all been suggested as means of setting percentage body fat guidelines, although each has major limitations.

OBJECTIVE

The aim of this study was to examine a potential new approach for developing percentage body fat ranges. The approach taken was to link healthy body mass index (BMI; in kg/m(2)) guidelines established by the National Institutes of Health and the World Health Organization with predicted percentage body fat.

DESIGN

Body fat was measured in subjects from 3 ethnic groups (white, African American, and Asian) who were screened and evaluated at 3 universities [Cambridge (United Kingdom), Columbia (United States), and Jikei (Japan)] with use of reference body-composition methods [4-compartment model (4C) at 2 laboratories and dual-energy X-ray absorptiometry (DXA) at all 3 laboratories]. Percentage body fat prediction equations were developed based on BMI and other independent variables.

RESULTS

A convenient sample of 1626 adults with BMIs < or =35 was evaluated. Independent percentage body fat predictor variables in multiple regression models included 1/BMI, sex, age, and ethnic group (R: values from 0.74 to 0.92 and SEEs from 2.8 to 5.4% fat). The prediction formulas were then used to prepare provisional healthy percentage body fat ranges based on published BMI limits for underweight (<18.5), overweight (> or =25), and obesity (> or =30).

CONCLUSION

This proposed approach and initial findings provide the groundwork and stimulus for establishing international healthy body fat ranges.

Brozek two-compartment model under-estimates body fat in black female athletes

The purpose of this study was to compare percentage body fat (%BF) values of black female athletes calculated using the Heymsfield four-compartment (4C), Brozek two-compartment (2C) and Schutte models. Eleven collegiate athletes underwent total body water (TBW) assessment, hydrostatic weighing (HW) and dual energy X-ray absorptiometry (DXA). Repeated-measures ANOVA determined that the 4C model yielded %BF values (16.2 +/- 1.5%) that were higher than the Brozek model (13.6 +/- 1.7%) but similar to the Schutte model (16.7 +/- 1.6%). The fat-free mass density of the athletes (1.109 +/- 0. 002 kg l-1) was significantly higher than the value 1.1 kg l-1 assumed by the 2C model. We conclude that in lean black female athletes, the Brozek 2C model under-estimates %BF, and that, if only HW is available, the Schutte model should be used to estimate %BF.

Human body composition: in vivo methods

In vivo methods used to study human body composition continue to be developed, along with more advanced reference models that utilize the information obtained with these technologies. Some methods are well established, with a strong physiological basis for their measurement, whereas others are much more indirect. This review has been structured from the methodological point of view to help the reader understand what can be examined with each technique. The associations between the various in vivo methods (densitometry, dilution, bioelectrical impedance and conductance, whole body counting, neutron activation, X-ray absorptiometry, computer tomography, and magnetic resonance imaging) and the five-level multicompartment model of body composition are described, along with the limitations and advantages of each method. This review also provides an overview of the present status of this field of research in human biology, including examples of reference body composition data for infants, children, adolescents, and adults.

Appendicular skeletal muscle mass: effects of age, gender, and ethnicity

This study tested the hypothesis that skeletal muscle mass is reduced in elderly women and men after adjustment first for stature and body weight. The hypothesis was evaluated by estimating appendicular skeletal muscle mass with dual-energy X-ray absorptiometry in a healthy adult cohort. A second purpose was to test the hypothesis that whole body 40K counting-derived total body potassium (TBK) is a reliable indirect measure of skeletal muscle mass. The independent effects on both appendicular skeletal muscle and TBK of gender (n = 148 women and 136 men) and ethnicity (n = 152 African-Americans and 132 Caucasians) were also explored. Main findings were 1) for both appendicular skeletal muscle mass (total, leg, and arm) and TBK, age was an independent determinant after adjustment first by stepwise multiple regression for stature and weight (multiple regression model r2 = approximately 0.60); absolute decrease with greater age in men was almost double that in women; significantly larger absolute amounts were observed in men and African-Americans after adjustment first for stature, weight, and age; and >80% of within-gender or -ethnic group between-individual component variation was explained by stature, weight, age, gender, and ethnicity differences; and 2) most of between-individual TBK variation could be explained by total appendicular skeletal muscle (r2 = 0.865), whereas age, gender, and ethnicity were small but significant additional covariates (total r2 = 0.903). Our study supports the hypotheses that skeletal muscle is reduced in the elderly and that TBK provides a reasonable indirect assessment of skeletal muscle mass. These findings provide a foundation for investigating skeletal muscle mass in a wide range of health-related conditions.