Development and validation of skinfold-thickness prediction equations with a 4-compartment model

Soft tissue material properties based on human abdominal in vivo macro-indenter measurements

Simulations of human-technology interaction in the context of product development require comprehensive knowledge of biomechanical in vivo behavior. To obtain this knowledge for the abdomen, we measured the continuous mechanical responses of the abdominal soft tissue of ten healthy participants in different lying positions anteriorly, laterally, and posteriorly under local compression depths of up to 30 mm. An experimental setup consisting of a mechatronic indenter with hemispherical tip and two time-of-flight (ToF) sensors for optical 3D displacement measurement of the surface was developed for this purpose. To account for the impact of muscle tone, experiments were conducted with both controlled activation and relaxation of the trunk muscles. Surface electromyography (sEMG) was used to monitor muscle activation levels. The obtained data sets comprise the continuous force-displacement data of six abdominal measurement regions, each synchronized with the local surface displacements resulting from the macro-indentation, and the bipolar sEMG signals at three key trunk muscles. We used inverse finite element analysis (FEA), to derive sets of nonlinear material parameters that numerically approximate the experimentally determined soft tissue behaviors. The physiological standard values obtained for all participants after data processing served as reference data. The mean stiffness of the abdomen was significantly different when the trunk muscles were activated or relaxed. No significant differences were found between the anterior-lateral measurement regions, with exception of those centered on the linea alba and centered on the muscle belly of the rectus abdominis below the intertubercular plane. The shapes and areas of deformation of the skin depended on the region and muscle activity. Using the hyperelastic Ogden model, we identified unique material parameter sets for all regions. Our findings confirmed that, in addition to the indenter force-displacement data, knowledge about tissue deformation is necessary to reliably determine unique material parameter sets using inverse FEA. The presented results can be used for finite element (FE) models of the abdomen, for example, in the context of orthopedic or biomedical product developments.

Estimating fat-free mass in recreationally resistance-trained young men: Longitudinal and cross-sectional validation of different methods

Several techniques exist to measure fat-free mass (FFM). Accordingly, this study is based on data from our recent trial comparing the sensitivity of the main field methods available with that of dual-energy X-ray absorptiometry (DXA) as reference and analyzing the cross-sectional accuracy of these field methods in recreationally resistance-trained males. We hypothesized that the use of these techniques would lead to varying estimates of FFM compared with DXA. Participants (N = 23; 21.4 ± 3.3 years) completed a 10-week resistance training plus diet intervention designed to optimize hypertrophy. FFM was determined by bioelectrical impedance analysis (BIA), 23 anthropometric equations, and DXA. After the intervention, FFM increased significantly according to BIA and most anthropometric estimates, but this increase was not detected by 2 anthropometric equations or by DXA. Only 1 of these 2 equations showed significant correlation with DXA and no standardized or significant differences to this reference method, although it did display significant heteroscedasticity. In our cross-sectional analysis, only 1 anthropometric equation gave rise to good accuracy as confirmed by DXA. Our findings indicate that the use of different techniques to assess FFM gains in response to a hypertrophic intervention yields different results. BIA with general embedded equations should not be used to monitor a young male adult's body composition. To monitor FFM over time, we would recommend the Dunne et al. equation (2) as the most sensitive field method, and to assess FFM cross-sectionally, equation (1) of these authors is the most accurate field method.

Evaluation of Skinfold Techniques in People with Down Syndrome: Development of a New Equation

The primary aim of this study was to evaluate the accuracy of skinfold thickness (SFT) measurements for the estimation of %Fat when compared to dual energy X-ray absorptiometry (DXA) in individuals with Down syndrome (DS). The secondary aim was to develop a new SFT-based body fat equation (SFT_NICKERSON). SFT-based %Fat was estimated using a body fat equation from González-Agüero (SFT_G-A) and body density conversion formulas from Siri (SFT_SIRI) and Brozek (SFT_BROZEK). Criterion %Fat was measured via DXA. SFT_G-A, SFT_SIRI, and SFT_BROZEK were significantly lower than DXA (mean differences ranged from -7.59 to -13.51%; all p < 0.001). The SEE values ranged from 3.47% (SFT_BROZEK) to 8.60% (SFT_G-A). The 95% limits of agreement were greater than ±10% for all comparisons. Mid-axilla and suprailium were significant predictors of %Fat (both p < 0.05). %Fat SFT_NICKERSON = 10.323 + (0.661 × mid-axilla) + (0.712 × suprailium). Age and all other skinfold sites were not statically significant in the regression model (all p > 0.05). Current findings indicate that SFT_G-A, SFT_SIRI, and SFT_BROZEK erroneously place an individual with excessive adiposity in a normal healthy range. Accordingly, the current study developed a new equation (SFT_NICKERSON) that can easily be administered in people with DS in a quick and efficient time frame. However, further research is warranted in this area.

Development and validation of anthropometric predictive equations that estimate the total body water and fat-free mass in Tunisian adults

OBJECTIVE

To develop and validate equations that estimate total body water (TBW) and fat-free mass (FFM) in adults using anthropometric measurements.

METHODS

A cross-sectional study was conducted among 178 adults (77 men and 101 women; aged 18-59 years). Participants were distributed by sex and age groups, and then randomly assigned to equal two groups; the development (n = 89) and the validation (n = 89). The anthropometric measurements included height and weight. The deuterium dilution technique (DDT) estimated TBW and FFM. Linear regression models were used with the TBW and FFM as the dependent variable, and height and weight as the independent variables. Cross-validation was performed by Bland and Altman plot, and the new anthropometric equations were developed.

RESULTS

In the validation sample, the developed equations had high R2 of 94.4 for both TBW and FFM in all age groups, and low standard errors (RMSE: 1.80 kg for TBW and 2.44 kg for FFM). The pure error was 2.03 for the TBW equation and 2.71 for the FFM equation. The Bland-Altman plot illustrated the good level of concordance between the TBW and FFM predicted by the new equations as determined by DDT. The following developed equations showed a better agreement with the DDT: [Formula: see text]; [Formula: see text].

CONCLUSION

In this study, we developed and validated prediction equations for the estimation of TBW and FFM from DDT in healthy adult Tunisian population. The newly anthropometric prediction equations seem to be the most accurate for Tunisian adult.

Dual energy X-ray absorptiometry produces larger measurement error in non-Hispanic Caucasians than Hispanics

BACKGROUND

Dual energy X-ray absorptiometry (DXA) is often used as a criterion measure in body composition research and in clinical settings for the estimate of body fat percent (%Fat). The accuracy of DXA for predicting %Fat has primarily been conducted in non-Hispanic populations.

AIM

The purpose of this study was to determine the agreement of DXA-derived %Fat in Hispanic and non-Hispanic Caucasian adults.

METHODS

The sample consisted of Hispanic males (n = 96) and females (n = 102) and non-Hispanic Caucasian males (n = 145) and females (n = 161). The %Fat of a whole-body DXA scan was compared against a criterion 4-compartment (4C) model via constant error (CE = DXA - 4C model) and 95% limits of agreement. Also, a 2 × 2 factorial ANOVA, using CE as a dependent variable, was conducted to examine the main and interaction effects of sex and ethnicity.

RESULTS

When compared to the 4C model, DXA overestimated %Fat by 4.0% in Hispanics and 5.5% in non-Hispanic Caucasians (all p < 0.05). The 95% limits of agreement ranged from ±5.5% to ±5.9% for all group comparisons. The 2 × 2 factorial ANOVA indicated the CE was greater in non-Hispanic Caucasians than Hispanics (CE difference = 1.5%; p < 0.05).

CONCLUSION

Our findings revealed that DXA significantly overestimates %Fat in both populations (Hispanics and non-Hispanic Caucasians), when compared to a 4C model, regardless of sex (male or female). However, the error is more profound in non-Hispanic Caucasian adults. It is worth nothing that DXA may be useful for tracking changes in body composition that occur throughout a lifestyle intervention. Nonetheless, practitioners should be aware that the estimate of %Fat from DXA may be larger than the actual values obtained from a 4C model.

Continuous Thermoregulatory Responses to a Mass-Participation 89-km Ultramarathon Road Race

PURPOSE

To continuously measure body core temperature (Tc) throughout a mass-participation ultramarathon in subelite recreational runners to quantify Tc magnitude and the influence of aerobic fitness and body fat.

METHODS

Twenty-three participants (19 men and 4 women; age 45 [9] y; body mass 72.0 [9.3] kg; body fat 26% [6%]; peak oxygen uptake 50 [6] mL·kg-1·min-1) had gastrointestinal temperature measured during an 89-km ultramarathon. Prerace-to-postrace changes in body mass, plasma sodium, and fluid and food recall quantified body water balance.

RESULTS

In maximal environmental conditions of 26.3 °C and 53% humidity, 21 of the 23 participants finished in 10:28 (01:10) h:min while replacing 49% (27%) of sweat losses, maintaining plasma sodium (140 [3] mmol·L-1), and dehydrating by 4.1% (1.3%). Mean maximum Tc was 39.0 (0.5) (range 38.2-40.1 °C) with 90% of race duration ≤39.0 °C. Mean maximum ΔTc was 1.9 (0.9) (0.9-2.7 °C) with 95% of race duration ≤2.0 °C. Over 0 to 45 km, associations between ΔTc and peak oxygen uptake (positive) and body fat (negative) were observed. Over 58 to 89 km, associations between Tc and peak oxygen uptake (negative) and body fat (positive) were observed.

CONCLUSIONS

Modest Tc responses were observed in recreational ultramarathon runners. Runners with higher levels of aerobic fitness and lower levels of body fat demonstrated the greatest changes in Tc during the first half of the race. Conversely, runners with lower levels of aerobic fitness and higher levels of body fat demonstrated the greatest absolute Tc in the final third of the race.

Official position of the Brazilian Association of Bone Assessment and Metabolism (ABRASSO) on the evaluation of body composition by densitometry: part I (technical aspects)—general concepts, indications, acquisition, and analysis

Objective

To review the technical aspects of body composition assessment by dual-energy X-ray absorptiometry (DXA) and other methods based on the most recent scientific evidence.

Materials and methods

This Official Position is a result of efforts by the Scientific Committee of the Brazilian Association of Bone Assessment and Metabolism (Associação Brasileira de Avaliação Óssea e Osteometabolismo, ABRASSO) and health care professionals with expertise in body composition assessment who were invited to contribute to the preparation of this document. The authors searched current databases for relevant publications. In this first part of the Official Position, the authors discuss the different methods and parameters used for body composition assessment, general principles of DXA, and aspects of the acquisition and analysis of DXA scans.

Conclusion

Considering aspects of accuracy, precision, cost, duration, and ability to evaluate all three compartments, DXA is considered the gold-standard method for body composition assessment, particularly for the evaluation of fat mass. In order to ensure reliable, adequate, and reproducible DXA reports, great attention is required regarding quality control procedures, preparation, removal of external artifacts, imaging acquisition, and data analysis and interpretation.

Optimizing Field Body Fat Percentage Assessment in Professional Soccer Players

Body composition is a determinant of performance in soccer. To estimate the body fat percentage (%BF), dual energy X-ray absorptiometry (DXA) is effective though this method is expensive and not readily accessible. This study examines the validity of widely used field methods based on anthropometric data and bioelectrical impedance analysis (BIA). Participants were 21 male Spanish First Division soccer players aged between 22 and 35 years. In each participant, body fat mass was determined by BIA and using 18 anthropometric equations including skinfold (SKF) measurements. DXA was used as reference. Correlation with DXA measurements was excellent for all equations and separate SKF measurements yet only moderate for BIA. However, only the equation recently developed for use in soccer players based on iliac crest and triceps SKFs showed no significant or standardized differences with DXA-derived %BF and these measurements also had the lowest bias. Our findings suggest that when DXA is not available, the best field method for %BF assessment in footballers is the equation based on iliac crest and triceps SKF. As another good option, we propose the sum of triceps, subscapular, supraspinal, and abdominal SKFs, as this combination also showed good correlation with DXA.

Maternal anthropometric measurements and correlation to maternal and fetal outcomes in late pregnancy

Background:

Body mass index does not distinguish between lean and fat body mass; therefore, its utility defining body composition is limited in pregnancy. Anthropometric measurements may better represent variation in body composition among women who are overweight or obese. We sought to examine body fat composition using maternal anthropometric measurements in late pregnancy and correlate with mode of delivery.

Methods:

A prospective study of pregnant patients who were overweight (body mass index: 25–29.9 kg/m²) or obese (body mass index ⩾ 30 kg/m²) with singleton pregnancies who underwent anthropometric measurements between 27 weeks, 0 days to 34 weeks, 6 days gestation. Maternal skinfold thicknesses from eight sites were used to estimate body fat mass. Correlation of skinfold thickness, anthroprometric measurements, and estimated body fat percentage on mode of delivery were analyzed with p < .05 as significant.

Results:

A total of 41 women with overweight (34.1%) or obese (65.9%) body habitus were included. Mean age was 29.9 years, and the majority (43.9%) were Black and 31.7% identified Hispanic/Latinx. The average gestational age at recruitment was 30 weeks, 2 days and 38 weeks, 6 days at delivery. A greater weight at recruitment (94.2 vs 81.8 kg, p = .023), waist circumference (47.1 vs 43.5 inches, p = .010), Huston–Presley body fat percentage (36.4% vs 31.8%, p = .030), triceps skinfold thickness (20.1 vs 15.7 mm, p = .030), biceps skinfold thickness (18.6 vs 15.0 mm, p = .042), and skinfold thickness, as well as sum of skinfold sites (83.3 vs 68.8 mm, p = .049) were associated with cesarean delivery compared to vaginal delivery on univariate analysis.

Conclusion:

Third-trimester anthropometric measurements may help predict increased risk for c-section in women with obesity. Further research may elucidate utility in nutritional counseling and delivery planning.

Validation of Non-empirical Fat-free Mass Estimation Model for a Wrist-worn Device

Fat-free mass (FFM) estimation has dramatic importance for body composition evaluation, often providing a basis for treatment of obesity and muscular dystrophy. However, current methods of FFM estimation have several drawbacks, usually related to either cost-effectiveness and equipment size (dual-energy X-ray absorptiometry (DEXA) scan) or model limitations. In this study, we present and validate a new FFM estimation model based on hand-to-hand bioimpedance analysis (BIA) and arm volume. Forty-two participants underwent a full-body DEXA scan, a series of anthropometric measurements, and upper-body BIA measurements with the custom-designed wearable wrist-worn impedance meter. A new two truncated cones (TTC) model was trained on DEXA data and achieved the best performance metrics of 0.886 ± 0.051 r², 0.052 ± 0.009 % mean average error, and 6.884 ± 1.283 kg maximal residual error in FFM estimation. The model further demonstrated its effectiveness in Bland-Altman comparisons with the skinfold thickness-based FFM estimation method, achieving the least mean bias (0.007 kg). The novel TTC model can provide an alternative to full-body BIA measurements, demonstrating an accurate FFM estimation independently of population variables.

Age and Training-Related Changes on Body Composition and Fitness in Male Amateur Cyclists

Master athletes are considered as a model of healthy aging because they can limit the age-related decline of physiological abilities compared to sedentary individuals. The main objective of this study is to analyze age-related changes and annual training on body composition (BC) and cardiorespiratory fitness (CRF) parameters. The participants in this retrospective cross-sectional study were 176 male cyclists, aged 40-60 years. BC was evaluated through anthropometric measurements and CRF was determined by an incremental cycle ergometer test to exhaustion. A comparative study between age groups was carried out through a one-way ANOVA test and the associations between the variables were assessed by Spearman's correlation coefficients and multiple regression analysis to estimate the performance. Training was generally associated with a decrease in both body weight and body fat (p < 0.05). A decrease in resting heart rate was observed as a vagal effect of kilometers cycled per year (p < 0.05). Kilometers cycled per year were associated with an increase in peak power output, which was larger in the master 40 group (p < 0.05) with a non-significant upward in VO2max (p > 0.05). In the performance prediction model, the included variables explained 52% of the variance. In summary, the changes induced by age were minimal in BC and negligible in CRF, whereas HR decreased with age. Training load was generally associated with a decrease in body weight, BMI and body fat percentage that was particularly notable in the abdominal skin folds. A decrease in HRrest was observed as a vagal effect due to kilometers cycled per year, and age did not seem to have a significant effect. The annual cycling kilometers were associated with to high PPO that is greater in the M40 group and a non-significant upward trend in VO2max.

Causative Mechanisms of Childhood and Adolescent Obesity Leading to Adult Cardiometabolic Disease: A Literature Review

The past few decades have shown a worrisome increase in the prevalence of obesity and its related illnesses. This increasing burden has a noteworthy impact on overall worldwide mortality and morbidity, with significant economic implications as well. The same trend is apparent regarding pediatric obesity. This is a particularly concerning aspect when considering the well-established link between cardiovascular disease and obesity, and the fact that childhood obesity frequently leads to adult obesity. Moreover, most obese adults have a history of excess weight starting in childhood. In addition, given the cumulative character of both time and severity of exposure to obesity as a risk factor for associated diseases, the repercussions of obesity prevalence and related morbidity could be exponential in time. The purpose of this review is to outline key aspects regarding the current knowledge on childhood and adolescent obesity as a cardiometabolic risk factor, as well as the most common etiological pathways involved in the development of weight excess and associated cardiovascular and metabolic diseases.

SMART STEP - SMARTphone-driven exercise and pedometer-based STEP intervention to promote physical activity among desk-based employees: Study protocol for a three-arm cluster randomized controlled trial

BACKGROUND

Prolonged sitting in desk-based office workers is found to be associated with increased cardiometabolic risk and poor cognitive performance. Technology-based physical activity (PA) interventions using smartphone applications (SmPh app) to promote PA levels might be effective in reducing cardiometabolic risk among sedentary population but the evidence remains inconclusive.

OBJECTIVE

The objective is to investigate the effects of a technology-based PA intervention compared to PA education with a worksite manual or no intervention on PA levels, cardiometabolic risk, cognitive performance, and work productivity among desk-based employees.

METHOD

A three-arm clustered randomized trial will be conducted. The study will be conducted among various administrative offices of a multifaceted university in India. Desk-based employees aged between 30 and 50 years (n = 159; 53 in each arm) will be recruited. Employees from various constituent institutions (clusters) of the university will be randomized into one of the three following groups - SMART: SmPh app-driven break reminders (visual exercise prompts) plus pedometer-based step intervention, TRADE: worksite PA education with a manual plus American College of Sports Medicine guided PA prescription, or CONTROL: usual work group. At baseline and after the 1st, 3rd and 6th month of the trial period, accelerometer-measured sitting time and PA levels, cardiometabolic risk (fasting blood glucose, triglycerides, insulin, blood pressure, heart rate variability, functional capacity, and subcutaneous fat), cognitive performance (executive function), sickness absenteeism and work limitations will be assessed by a blinded assessor. Therapist delivering interventions will not be blinded.

CONCLUSION

This trial will determine whether a combined SmPh-app and pedometer-based intervention is more effective than education or no intervention in altering PA levels, cardiometabolic risk and cognitive performance among desk-based employees in India. This study has the potential to foster institutional recommendations for using SmPh-based technology and pedometers to promote PA and reduce sedentary behavior at work.

Generalized Equations for Predicting Percent Body Fat from Anthropometric Measures Using a Criterion Five-Compartment Model

INTRODUCTION

Anthropometric-based equations are used to estimate percent body fat (%BF) when laboratory methods are impractical or not available. However, because these equations are often derived from two-compartment models, they are prone to error due to assumptions regarding fat-free mass composition. The purpose of this study was to develop a new anthropometric-based equation for the prediction of %BF, using a five-compartment (5C) model as the criterion measure.

METHODS

A sample of healthy adults (52.2% female; age, 18 to 69 y; body mass index [BMI], 15.7 to 49.5 kg·m-2) completed hydrostatic weighing, dual-energy X-ray absorptiometry, and bioimpedance spectroscopy measurements for calculation of 5C %BF (%BF5C), as well as skinfolds and circumferences. %BF5C was regressed on anthropometric measures using hierarchical variable selection in a random sample of subjects (n = 279). The resulting equation was cross-validated in the remaining participants (n = 78). New model performance was also compared to several common anthropometric-based equations.

RESULTS

The new equation [%BFNew = 6.083 + (0.143 × SSnew) - (12.058 × Sex) - (0.150 × Age) - (0.233 × BMI) + (0.256 × Waist) + (0.162 × Sex×Age)] explained a significant proportion of variance in %BF5C (R2 = 0.775, SEE = 4.0%). Predictors included sum of skinfolds (SSnew, midaxillary, triceps, and thigh) and waist circumference. The new equation cross-validated well against %BF5C when compared to other existing equations, producing a large intraclass correlation coefficient (ICC = 0.90), small mean bias and limits of agreement (0.4 ± 8.6%), and small measures of error (SEE = 2.5%).

CONCLUSION

%BFNew improved on previous anthropometric-based equations, providing better overall agreement and less error in %BF estimation. The equation described in this study may provide an accurate estimate of %BF5C in healthy adults when measurement is not practical.

Changes in Liver Enzymes and Metabolic Profile in Adolescents with Fatty Liver following Exercise Interventions

PURPOSE

Nonalcoholic fatty liver disease (NAFLD) is the most frequent cause of chronic liver diseases in both adults and children with obesity. The aim of this study was to compare the changes in liver enzymes and metabolic profile in adolescents with fatty liver following selected school-based exercise (SBE) and high-intensity interval training (HIIT) interventions.

METHODS

In a semi-experimental study, 34 obese male adolescents with clinically defined NAFLD were divided into the HIIT (n=11, age=12.81±1.02 years, body mass index [BMI]=26.68 ±2.32 kg/m²), selected SBE (n=11, age=13.39±0.95 years, BMI=26.47±1.74 kg/m²), and control (n=12, age=13.14±1.49 years, BMI=26.45±2.21 kg/m²) groups. The ultrasonography NAFLD grade, peak oxygen uptake (VO_2peak), lipid profile, insulin resistance, and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels of the participants were measured before and after the exercise interventions.

RESULTS

The BMI, waist-to-hip ratio, and body fat percentage of the participants decreased, and a significant increase in VO_2peak was observed after the intervention; however, the HIIT group showed a significant improvement compared with the SBE group (p<0.01). Significant reductions were observed in the levels of insulin resistance, triglyceride, total cholesterol, ALT, and AST in both groups, although high-density lipoprotein levels decreased only in the HIIT group (p<0.01). Further, a significant reduction in low-density lipoprotein level was observed in the training groups (p<0.01), but this decrease was not significant compared with the control group (p>0.01).

CONCLUSION

HIIT and SBE are equally effective in improving health parameters in obese children and adolescents.

Development and Cross-Validation of Anthropometric Predictive Equations to Estimate Total Body Fat Percentage in Adult Women in Sri Lanka

Attempts have been made to estimate body fat using anthropometry, and most of them are country-specific. This study was designed to develop and cross-validate anthropometric predictive equations to estimate the total body fat percentage (TBFP) of Sri Lankan adult women. A cross-sectional study was conducted in Galle, Sri Lanka, with two groups: Group A (group for equation development) and Group B (cross-validation group) (n = 175 each) of randomly selected healthy adult women aged 30-60 years. TBFP (%) was quantified with total body DXA (TBFPDXA). Height (m), weight (kg), and skinfold thickness (SFT, mm) at six sites and circumferences (cm) at five sites were measured. In the first step, four anthropometric equations were developed based on the data obtained from multiple regression analyses (TBFPDXA = dependent variable and anthropometric measurements and age = independent variables) with Group A. They were developed on the basis of circumferences (TBFP1), SFTs (TBFP2), circumferences and SFTs (TBFP3), and highly significant circumferences and SFTs (r ≥ 0.6) (TBFP4). In the second step, the newly developed equations were cross-validated using Group B. Three equations (TBFP1, TBFP2, and TBFP4) showed the agreement with cross-validation criteria. There were no differences between TBFPDXA and TBFP estimated by these equations (p > 0.05). They showed higher measurement concordance with TBFPDXA; correlation between measured TBFP with DXA and estimated with TBFP1, TBFP2, and TBFP4, respectively, was 0.80 (R 2 = 0.65, SEE = 3.10), 0.83 (R 2 = 0.69, SEE = 2.93), and 0.84 (R 2 = 0.72, SEE = 2.78). Three anthropometric measurements based on predictive equations were developed and cross-validated to satisfactorily estimate the TBFP in adult women.

Direct Comparison of (Anthropometric) Methods for the Assessment of Body Composition

OBJECTIVE

Several methods for the assessment of body composition exist, yet they yield different results. The present study aimed to assess the extent of these differences on a sample of young, healthy subjects. We hypothesised that differences in body composition results obtained with different methods will vary to the extent that a subject can be misclassified into different nutritional categories.

RESEARCH METHODS AND PROCEDURES

Underwater weighing (UWW), bioelectrical impedance analysis (BIA), anthropometry (ANT), and dual-energy X-ray absorptiometry (DXA) were used to assess body composition. An extensive list of ANT regression equations (or sets of equations) was analysed in terms of accuracy and precision relative to DXA.

RESULTS

When DXA-determined body fat (BF) values were taken as a reference, UWW overestimated BF in both genders. In contrast, BIA (measured with a given bioimpedance analyser) underestimated BF in females, although BIA-determined BF did not differ from DXA in males. A huge difference in BF estimates (8-29% for females and 6-29% for males, for DXA-determined BF of 25.5% and 13.9% for females in males, respectively) was observed across a number of ANT regression equations; yet, ANT proved not to be inferior to DXA, provided that regression equations with the highest combinations of accuracy and precision were chosen.

CONCLUSIONS

The study proved grounds for comparison of body composition results of young, healthy subjects, obtained with different methods and across a wide range of ANT regression equations. It also revealed a list of the most appropriate ANT regression equations for the selected sample and reported their accuracy and precision.

How Does Variation in the Body Composition of Both Stimuli and Participant Modulate Self-Estimates of Men's Body Size?

When measured in units of body mass index (BMI), how much variation in men's self-estimates of body size is caused by i) variation in participants' body composition and ii) variation in the apparent muscle mass and muscle tone of the stimuli being judged? To address this, we generated nine sets of male CGI bodies representing low, mid, and high muscle mass rendered at low, mid, and high muscle tone, from 18.75 to 40 BMI_hse units. BMI_hse units in this study are estimates of BMI derived from calibration equations predicting BMI from waist and hip circumference, age, sex, height, and ethnicity in the Health Survey for England databases. Forty-five healthy adult men estimated their body size using a yes-no paradigm for each combination of muscle mass/tone. We also measured participants' body composition with Harpenden callipers and their body concerns with psychometric questionnaires. We show that stimulus variation in apparent muscle mass/tone can introduce differences up to ∼2.5 BMI_hse units in men's self-estimates of body size. Moreover, men with the same actual BMI, but different body composition, showed up to ∼5-7 BMI_hse unit differences in self-estimates of body size. In the face of such large errors, we advocate that such judgments in men should be made instead by simultaneously manipulating both the adiposity and the muscle mass of stimuli which are appropriately calibrated for body composition, so that the participant can match the body size and shape they believe themselves to have to the stimulus they see.

External Validation of Equations that Use Demographic and Anthropometric Measurements to Predict Percent Body Fat

OBJECTIVE

Numerous equation to predict percent body fat using demographics and anthropometrics have been published but external validation of these equations is limited. The objective of this study was to validate published equations that use anthropometrics for prediction of percent body fat using external data.

METHODS

Data were from the Visceral Fat, Metabolic Rate, and Coronary Heart Disease Risk I (VIM I) Study and the Fels Longitudinal Study (Fels). VIM I was conducted in a subset of subjects from the CARDIA study and included black and white adults 28-40 years (n = 392). Fels consisted of white participants 8-88 years (n = 1,044). Percent body fat assessed by dual X-ray absorptiometry (DXA) in these two studies was compared to results calculated using 13 equations from Stevens et al. and nine other published equations.

RESULTS

In general, the Stevens equations performed better than equations from other studies. For example, equation "I" in women in VIM I, Fels adults, and Fels youth, R2 estimates were 0.765, 0.757 and 0.789, respectively. In men the estimates were 0.702 in VIM I, 0.822 in Fels adults and 0.905 in Fels youth. None of the results from the nine published equations showed R2 this high in corresponding groups.

CONCLUSIONS

Our results indicate that several of the Stevens equations have external validity superior to that of nine other published equations among varying age groups, genders and races.

Accuracy of Anthropometric Equations for Estimating Body Fat in Professional Male Soccer Players Compared with DXA

Background

There are several published anthropometric equations to estimate body fat percentage (BF%), and this may prompt uncertainty about their application.

Purpose

To analyze the accuracy of several anthropometric equations (developed in athletic [AT] and nonathletic [NAT] populations) that estimate BF% comparing them with DXA.

Methods

We evaluated 131 professional male soccer players (body mass: 73.2 ± 8.0 kg; height: 177.5 ± 5.8 cm; DXA BF% [median, 25th–75th percentile]: 14.0, 11.9–16.4%) aged 18 to 37 years. All subjects were evaluated with anthropometric measurements and a whole body DXA scan. BF% was estimated through 14 AT and 17 NAT anthropometric equations and compared with the measured DXA BF%. Mean differences and 95% limits of agreement were calculated for those anthropometric equations without significant differences with DXA.

Results

Five AT and seven NAT anthropometric equations did not differ significantly with DXA. From these, Oliver's and Civar's (AT) and Ball's and Wilmore's (NAT) equations showed the highest agreement with DXA. Their 95% limits of agreement ranged from −3.9 to 2.3%, −4.8 to 1.8%, −3.4 to 3.1%, and −3.9 to 3.0%, respectively.

Conclusion

Oliver's, Ball's, Civar's, and Wilmore's equations were the best to estimate BF% accurately compared with DXA in professional male soccer players.

Skinfold Thickness Measurement in Term Nigerian Neonates: Establishing Reference Values

Skin fold thickness (SFT) measurement is a reliable, cheap, simple, noninvasive method of body fat estimation at all ages including the neonatal period. Objective. To determine reference values of biceps, triceps, subscapular, and suprailiac skinfold thickness measurements in term Nigerian newborns. Method. A prospective cross-sectional study over a six-month period (Dec 2010-May 2011) was carried out on term and healthy neonates delivered between 37 and 41 weeks. The anthropometric measurements were taken within the first 48 hours of life including the skinfold thickness. The skinfold thickness measurements were taken at four sites, namely, triceps, biceps, subscapular, and suprailiac, using Harpenden skinfold calipers. The mean of two readings was recorded. Result. A total of one thousand one hundred and sixty-eight neonates were studied. The birth weight ranged between 2000 g and 5000 g with a mean birth weight of the neonates at 3259 ± 470 g. The mean birth weight of the males (3339 ± 0.45) was significantly higher than that of females (3200 ± 0.44) (p < 0.0001). Female neonates had higher mean values of triceps, subscapular, and suprailiac skinfold thickness (p < 0.001, resp.) while male neonates had higher mean value of biceps skinfold thickness (p = 0.008). Females also had higher mean values of the sum of skinfold thicknesses at all four sites and the sum at the two truncal sites at every stratified gestational age. Conclusions. The sex specific percentile chart developed for skinfold thickness measurements can be used to detect deviation from the reference population such that infants who are at risk of nutritional or health problems are identified early, and intervention is instituted promptly.

Estimation of body fat in Pakistani adult: A comparison of equations based upon skinfold thickness measurements

Objective:

To compare three different body fats estimation equations using skin fold measurements with bioelectrical impedance analysis.

Methods:

A total of 130 subjects were included from Department of Endocrinology and Metabolism, Services Hospital, Lahore from 1^st April 2016 to 30^th Sep. 2016. The triceps, biceps, subscapular, chest, thigh, abdominal, suprailiac skinfold thickness of the subjects was measured with skin-fold calipers (Harpenden) on non-dominant side. The percentage fat mass (%FM) predicted by using each skin-fold-thickness equations namely Durnin & Womersley, Jackson & Pollock and Sloan was compared with %FM measured using a bioelectrical impedance analyzer (BIA).

Results:

The mean age of subjects was 48.75±10.7 years, mean BMI was 29.08±6.09 kg/m². The mean %FM calculated by Durnin & Womersley (32.408±0.584), Jackson & Pollock (24.658±0.527), Sloan (20.40±0.545). The %FM by BIA was 38.182±0.529. All three equations showed positive correlation but underestimated %FM as compared to BIA.

Conclusion:

All three BF estimation equations underestimate body fat percentage compared to BIA. Among the three, Durnin & Womersley equation shows best positive correlation and hence it can be used for estimation of percentage fat mass as an alternate to BIA.

Assessment of Abdominal Muscle's Maximal Force of Contraction Using Surface EMG in Inguinal Hernia Patients

INTRODUCTION

Reduction in abdominal muscle's strength has been implicated in the development of inguinal hernia. Patients with inguinal hernia on one side are shown to be at higher risk of developing inguinal hernia on the other side.

AIM

To assess the abdominal muscle strength in inguinal hernia subjects using surface Electromyography (EMG) and compare it with healthy controls.

MATERIALS AND METHODS

This is a cross-sectional study involving only male subjects. Abdominal (Inguinal) hernia subjects without any known complications were recruited from surgery department and the accompanying healthy individuals were taken as control (Control, n=44, inguinal hernia subjects, n=43). The subjects were asked to perform maximal contraction for three seconds targeting external and internal oblique muscles of right and left sides separately. Motor unit potentials were recorded using surface EMG for individual muscles on both sides during maximal contraction. The maximum amplitude of the motor unit potentials obtained was considered as the strength of the respective muscle.

RESULTS

In control group, there was no significant difference in strength of external and internal oblique muscles between the two sides. Strength of external and internal oblique muscles of both herniated and unaffected side was reduced in inguinal hernia subjects as compared to healthy controls. Further, the muscle strength of herniated side was less as compared to unaffected side in the inguinal hernia subjects.

CONCLUSION

Abdominal muscle strength is reduced in hernia subjects and even the apparently normal side strength is less as compared to controls. This should be considered while performing corrective surgeries in inguinal hernia subjects.

A field tool for prediction of body fat in Sri Lankan women: skinfold thickness equation

BACKGROUND

Valid skinfold thickness (SFT) equations for the prediction of body fat are currently unavailable for South Asian women and would be a potentially robust field tool. Our aim was to assess the validity of existing SFT equations against deuterium (²H₂O) dilution and, if invalid, to develop and validate an SFT equation for % fat mass (%FM) in Sri Lankan women.

METHODS

H₂O dilution was used with Fourier transform infrared (FTIR) spectroscopy as the criterion method for the assessment of %FM in urban Sri Lankan women (30-45 years). This data was used to assess the validity of available SFT equations and to generate and validate a new SFT equation for the prediction of %FM against the criterion method. Women (n = 164) were divided into validation and cross-validation groups for the development and validation of the new equation. The level of agreement between the %FM calculated by the final derived prediction equation and the %FM obtained by ²H₂O dilution was assessed using Pearson's correlation coefficient (R) and Bland Altman plots. Student's t test was used to assess over- or underestimation, and significance was set at p < 0.05.

RESULTS

Existing equations significantly (p < 0.001) underestimated %FM compared with the ²H₂O dilution method. The final equation obtained was %FM = 19.621 + (0.237*weight) + (0.259*triceps). When compared with ²H₂O dilution, %FM by the equation was not significantly different. There was a significant (p < 0.001) correlation between %FM by the reference method and %FM by the equation. The limit of agreement by Bland Altman plot was narrow with a small mean positive bias.

CONCLUSIONS

Existing SFT equations were not applicable to this population. The new equation derived was valid. We report a new SFT equation to predict %FM in women of South Asian ancestry suitable for field use.

Deficiencies of macronutrient intake among HIV-positive breastfeeding women in Dar es Salaam, Tanzania

We compared macronutrient intake, food insecurity, and anthropometrics in breastfeeding women: 40 HIV-positive women not yet on antiretroviral therapy and 40 HIV-negative women. Calculated deficits at 2 weeks were 517 kcal per day for HIV-positive women vs 87 kcal per day surplus for HIV-negative women (P = 0.01) and 29 g protein per day for HIV-positive women vs 16 g protein per day for HIV-negative women (P = 0.04). Food insecurity scores were 11.3 for HIV-positive women vs 7.8 for HIV-negative women (P < 0.01). Enhanced dietary education together with macronutrient supplementation may be required to improve health outcomes in HIV-positive women and their infants.

Percent body fat prediction equations for 8- to 17-year-old American children

BACKGROUND

Percent body fat equations are usually developed in specific populations and have low generalizability.

OBJECTIVES

To use a nationally representative sample of the American youth population (8-17 years old) from the 1999-2004 National Health and Nutrition Examination Survey data to develop gender-specific percent body fat equations.

METHODS

Percent body fat equations were developed for girls and boys using information on weight, height, waist circumference, triceps skin-folds, age, race/ethnicity and menses status compared to dual-emission X-ray absorptiometry. Terms were selected using forward and backward selection in regression models in a 2/3 development sample and were cross-validated in the remaining sample. Final coefficients were estimated in the full sample.

RESULTS

Final equations included ten terms in girls and eight terms in boys including interactions with age and race/ethnicity. In the cross-validation sample, the adjusted R2 was 0.818 and the root mean squared error was 2.758 in girls. Comparable estimates in boys were 0.893 and 2.525. Systematic bias was not detected in the estimates by race/ethnicity or by body mass index categories.

CONCLUSION

Gender-specific percent body fat equations were developed in youth with a strong potential for generalizability and utilization by other investigators studying adiposity-related issues in youth.

Methodologies to assess paediatric adiposity

INTRODUCTION

Childhood obesity is associated with increased risk of adult obesity, cardiovascular disease, diabetes and cancer. Appropriate techniques for assessment of childhood adiposity are required to identify children at risk. The aim of this review was to examine core clinical measurements and more technical tools to assess paediatric adiposity.

METHODS

The online databases PubMed, CINALH and EMBASE were searched and the abstracts identified were reviewed to determine appropriate studies. Their reference lists were also searched to identify further eligible studies. Publications were included if they described childhood measurement techniques or involved validation.

RESULTS AND DISCUSSION

There are many body composition assessment tools available, none of which are direct. Each technique has limitations and a combination of methods may be used. The main clinical techniques are weight, height, body mass index (BMI) and circumferences which provide sufficient information to enable classification of overweight or obesity when growth centile charts and ratios are employed. Further investigation depends on resources available and examiner skill. Skinfold thicknesses are cost-effective but require technical training and only measure subcutaneous fat. Dual energy X-ray absorptiometry (DEXA), air displacement plethysmography (ADP), magnetic resonance imaging (MRI) and computed tomography (CT) are more costly and intensive, requiring the child to remain still for longer periods. DEXA and ADP are capable of accurately measuring adiposity but are unable to distinguish between fat depots. MRI and CT can distinguish intra-abdominal from subcutaneous adiposity and are considered gold standards, but CT is unsuitable for adiposity measurement in children due to high levels of radiation exposure. Ultrasound is a promising technique capable of measuring intra-abdominal adiposity in children but requires further validation.

CONCLUSION

The core clinical measurements of weight, height, BMI and circumferences are sufficient to enable diagnosis of paediatric overweight and obesity while more technical tools provide further insight.

Comparison of anthropometric-based equations for estimation of body fat percentage in a normal-weight and overweight female cohort: validation via air-displacement plethysmography

OBJECTIVE

To evaluate the accuracy of the most commonly used anthropometric-based equations in the estimation of percentage body fat (%BF) in both normal-weight and overweight women using air-displacement plethysmography (ADP) as the criterion measure.

DESIGN

A comparative study in which the equations of Durnin and Womersley (1974; DW) and Jackson, Pollock and Ward (1980) at three, four and seven sites (JPW₃, JPW₄ and JPW₇) were validated against ADP in three groups. Group 1 included all participants, group 2 included participants with a BMI <25·0 kg/m² and group 3 included participants with a BMI ≥25·0 kg/m².

SETTING

Human Performance Laboratory, Institute for Sport and Health, University College Dublin, Republic of Ireland.

SUBJECTS

Forty-three female participants aged between 18 and 55 years.

RESULTS

In all three groups, the %BF values estimated from the DW equation were closer to the criterion measure (i.e. ADP) than those estimated from the other equations. Of the three JPW equations, JPW₃ provided the most accurate estimation of %BF when compared with ADP in all three groups.

CONCLUSION

In comparison to ADP, these findings suggest that the DW equation is the most accurate anthropometric method for the estimation of %BF in both normal-weight and overweight females.

Body composition assessment in infancy and early childhood: comparison of anthropometry with dual-energy X-ray absorptiometry in low-income group children from India

BACKGROUND/OBJECTIVE

Anthropometry is a simple, inexpensive method of body composition assessment, but its validity has not been examined adequately in young children. The study therefore compared the body composition estimates using anthropometry with those using dual-energy X-ray absorptiometry (DXA) in infants and young children.

METHODS

Body composition estimates using anthropometry and DXA were assessed and compared at 6, 12 and 18 months in a cohort of 137 infants enrolled at birth.

RESULTS

Fat mass (FM) and body fat percent (%BF) estimates by anthropometry were lower than those using DXA. Mean differences (DXA-skinfold thickness) in FM, fat free mass (FFM) and %BF were highest at 6 months (350 g, -226 g and 4%, respectively); the differences reduced with increase in age and were lowest at 18 months (46 g, 56 g and 0%, respectively). Bland-Altman analyses showed good agreement between the FM, FFM and %BF estimates by the two methods only at 18 months. Accretion of FM and FFM during follow-up, estimated by the two methods, was significantly different, with agreement between the methods seen only for increment in FFM from 6 to 12 months.

CONCLUSIONS

Substantial differences were found in the body composition estimates by anthropometry compared with DXA and also in the longitudinally assessed tissue accretion patterns by the two methods. As the body composition patterns may be influenced by the method used for body composition assessment, results of studies assessing body composition by anthropometry during infancy should be interpreted with caution.

A comparison of body composition measurement techniques

BACKGROUND

An understanding of the reproducibility of body composition measurements is essential for effective intervention studies. Air displacement plethysmography (ADP) and bioelectrical impedance (BIA) are two easy-to-use measures of body composition. The present study aimed to assess the reproducibility of ADP and BIA and compare them with each other, as well as with skinfold measurement.

METHODS

Forty-one participants were tested on two occasions following an overnight fast. On test day 1, participants' height, weight and % body fat (BF) were measured using ADP and BIA. Measurements were replicated to assess the within-day reproducibility. On test day 2, participants were again tested using ADP and BIA and had skinfold measurements taken. Three skinfold equations for BF calculation were applied. Comparisons of within- and between-day reproducibility and between measurement techniques were completed using Pearson correlations and Bland-Altman analysis.

RESULTS

Both Pearson correlation and Bland-Altman analysis showed good within- and between-day relationships and agreement for BF from ADP and BIA measurements. The two methods had a high correlation between them; however, the mean difference between the two was 3.1% (4.1%). From the skinfold equations used, the best agreement with ADP had a mean difference of 0.3% (0.8%) and, with BIA, had mean differences of 1.9% (4.2%).

CONCLUSIONS

The data indicate that ADP and BIA cannot be used interchangeably, although both measurements had good within- and between-day agreement.

Nutritional status of HIV-infected women with tuberculosis in Dar es Salaam, Tanzania

SETTING

Tuberculosis (TB) treatment clinics in Dar es Salaam, Tanzania.

OBJECTIVE

To quantify anthropometrics and intake of en-ergy and protein among human immunodeficiency virus (HIV) positive women with TB.

DESIGN

HIV-positive women with newly diagnosed TB were assessed on their anthropometric characteristics and dietary intake. Energy and protein intake were determined using Tanzania food composition tables and compared with standard recommendations. Patients were re-evaluated after 4-6 months of anti-tuberculosis treatment.

RESULTS

Among 43 women, the baseline median CD4 count was 209 cells/µl (range 8-721); 19 (44%) had a CD4 count of <200; 20 (47%) were on antiretroviral therapy. Body mass index was <18.5 kg/m(2) in 25 (58%); the median food insecurity score was 6. The median level of kcal/day was 1693 (range 1290-2633) compared to an estimated need of 2658; the median deficit was 875 kcal (range -65-1278). The median level of protein/day was 42 g (range 27-67) compared to 77 g estimated need; the median protein deficit was 35 g (range 10-50). The median weight gain among 29 patients after 4-6 months was 6 kg.

CONCLUSION

HIV-positive women with TB have substantial 24-h deficits in energy and protein intake, report significant food insecurity and gain minimal weight on anti-tuberculosis treatment. Enhanced dietary education together with daily supplementation of 1000 kcal with 40 g protein may be required.

Development and validation of anthropometric prediction equations for estimation of lean body mass and appendicular lean soft tissue in Indian men and women

Lean body mass (LBM) and muscle mass remain difficult to quantify in large epidemiological studies due to the unavailability of inexpensive methods. We therefore developed anthropometric prediction equations to estimate the LBM and appendicular lean soft tissue (ALST) using dual-energy X-ray absorptiometry (DXA) as a reference method. Healthy volunteers (n = 2,220; 36% women; age 18-79 yr), representing a wide range of body mass index (14–44 kg/m²), participated in this study. Their LBM, including ALST, was assessed by DXA along with anthropometric measurements. The sample was divided into prediction (60%) and validation (40%) sets. In the prediction set, a number of prediction models were constructed using DXA-measured LBM and ALST estimates as dependent variables and a combination of anthropometric indices as independent variables. These equations were cross-validated in the validation set. Simple equations using age, height, and weight explained >90% variation in the LBM and ALST in both men and women. Additional variables (hip and limb circumferences and sum of skinfold thicknesses) increased the explained variation by 5–8% in the fully adjusted models predicting LBM and ALST. More complex equations using all of the above anthropometric variables could predict the DXA-measured LBM and ALST accurately, as indicated by low standard error of the estimate (LBM: 1.47 kg and 1.63 kg for men and women, respectively), as well as good agreement by Bland-Altman analyses (Bland JM, Altman D.Lancet 1: 307–310, 1986). These equations could be a valuable tool in large epidemiological studies assessing these body compartments in Indians and other population groups with similar body composition.

Glycaemic index of meals affects appetite sensation but not energy balance in active males

BACKGROUND

Foods with low glycaemic index (LGI) are reported to suppress appetite mainly in overweight population but have not been investigated in athletic adults.

OBJECTIVE

The aim of this study was to compare the short-term effects of LGI and high GI (HGI) meals over a day on subsequent subjective appetite sensation, energy intake, energy expenditure, energy balance and resting metabolic rate in physically active males.

METHODS

This cross-sectional randomized crossover study included 14 active males (mean ± SD; age 34.5 ± 8.9 years, body mass index 22.8 ± 2.1 kg m(-2)) to consume LGI and HGI meals on two separate days. On each trial day, participants consumed a breakfast in the laboratory and then left with a packed lunch, dinner and snacks. Appetite scores, energy intake and expenditure were assessed.

RESULTS

The area under the curve for appetite scores of the HGI trial was significantly smaller than that of the LGI trial during the laboratory period (p = 0.027) and throughout the day (p = 0.009). No significant differences in energy intake, energy expenditure, energy balance and resting metabolic rate were found between groups, between the trial days and between the corresponding post-trial days.

CONCLUSIONS

These results show that frequent ingestion of the HGI meals, contrary to the previous reports, suppresses appetite more than that of LGI meals, but did not affect energy balance in physically active normal-weight males.

Improved Prediction of Body Fat by Measuring Skinfold Thickness, Circumferences, and Bone Breadths

OBJECTIVE

To develop improved predictive regression equations for body fat content derived from common anthropometric measurements.

RESEARCH METHODS AND PROCEDURES

117 healthy German subjects, 46 men and 71 women, 26 to 67 years of age, from two different studies were assigned to a validation and a cross-validation group. Common anthropometric measurements and body composition by DXA were obtained. Equations using anthropometric measurements predicting body fat mass (BFM) with DXA as a reference method were developed using regression models.

RESULTS

The final best predictive sex-specific equations combining skinfold thicknesses (SF), circumferences, and bone breadth measurements were as follows: BFM(New) (kg) for men = -40.750 + {(0.397 x waist circumference) + [6.568 x (log triceps SF + log subscapular SF + log abdominal SF)]} and BFM(New) (kg) for women = -75.231 + {(0.512 x hip circumference) + [8.889 x (log chin SF + log triceps SF + log subscapular SF)] + (1.905 x knee breadth)}. The estimates of BFM from both validation and cross-validation had an excellent correlation, showed excellent correspondence to the DXA estimates, and showed a negligible tendency to underestimate percent body fat in subjects with higher BFM compared with equations using a two-compartment (Durnin and Womersley) or a four-compartment (Peterson) model as the reference method.

DISCUSSION

Combining skinfold thicknesses with circumference and/or bone breadth measures provide a more precise prediction of percent body fat in comparison with established SF equations. Our equations are recommended for use in clinical or epidemiological settings in populations with similar ethnic background.

Validation of five simple models estimating body fat in white postmenopausal women: use in clinical practice and research

The aim of this study was to validate noninvasive models, retrieved from the literature, estimating body fat in white women. The cohort used for the validation consisted of 277 postmenopausal women, and the reference method was dual-energy X-ray absorptiometry (DXA). Five models were retrieved containing anthropometric measurements such as bicep and tricep skinfolds, waist circumference (WC), height, and body weight. Models including only BMI were found to be less biased and more valid than others including skinfolds and circumferences. The model by Visser et al., estimating body density (BD = 0.0226 × sex - 0.0022 × BMI + 1.0605) with the subsequent use of Brozek's (and not Siri's) equation to estimate body fat percentage (%BF), was found to be more valid than the other models for this cohort. In conclusion, it seems that Visser's et al. model, including only BMI, with Brozek's equation, is a fast, noninvasive, and valid method to assess body composition in white postmenopausal women in clinical practice and research.

The Bland-Altman method should not be used in regression cross-validation studies

The purpose of this study was to demonstrate the bias in the Bland-Altman (BA) limits of agreement method when it is used to validate regression models. Data from 1,158 men were used to develop three regression equations to estimate maximum oxygen uptake (R2 = .40, .61, and .82, respectively). The equations were evaluated in a cross-validation sample of 581 men. The BA means and differences were correlated (p < .001) in the cross-validation sample for each model (r = .55, .39, and .26, respectively), thus demonstrating bias. The BA method is inappropriate for validation of regression models. Validation of regression equations is properly conducted by plotting the residuals against the estimated values and examining the magnitude of the estimation error.

Predicting fat percent by skinfolds in racial groups: Durnin and Womersley revisited

PURPOSE

Despite their widespread use in research and fitness settings, Durnin and Womersley's (DW) 1974 prediction equations using skinfold thickness to estimate body fat percent by hydrodensitometry have not been systematically evaluated in racial or ethnic groups using body fat percent measured by dual-energy x-ray absorptiometry (%BF(DXA)) as the standard.

METHODS

This cross-sectional, population-based study examined whether the DW skinfold equations predict %BF(DXA) in a large, multiracial sample. Four skinfold measures (biceps, triceps, subscapular, and suprailiac), other clinical anthropometrics, and %BF(DXA) were obtained from 1675 healthy adults, age 18-110 yr, who were classified into four racial or ethnic categories: Caucasian, African American, Hispanic, or Asian. Predicted body fat percent using DW equations was compared with %BF(DXA) and evaluated within race/ethnicity- and sex-specific groups.

RESULTS

Mean body fat percent predicted by DW equations was significantly different from %BF(DXA) in four of eight race/ethnicity- and sex-specific groups, particularly in Asian women and African American men (3.3 and 2.4 percentage point overestimates, respectively, P < 0.0001). New linear regression equations were developed estimating %BF(DXA) specific to each race/ethnicity and sex group, using the original DW skinfold sites. Body weight, height, and waist circumference independently predicted fat percent and were also included in the new equations.

CONCLUSIONS

The 1974 DW equations did not predict %BF(DXA) uniformly in all races or ethnicities. Using %BF(DXA) as the criterion measure, the original DW skinfold equations have been updated specific to sex and race/ethnicity while maintaining the DW options for a minimalistic model using fewer predictors.