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

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.

Thigh circumference as a useful predictor of body fat in adolescent girls with anorexia nervosa

BACKGROUND/AIM

Girls with anorexia nervosa (AN) demonstrate severe depletion of body fat. The aim of this study was to determine an accurate anthropometric measurement for clinical assessment of fat depletion in girls with AN in connection with body composition measured by dual-energy X-ray absorptiometry (DXA).

METHODS

In 64 female AN patients aged 12.8-23.1 years (mean 16.0 ± 1.8), body mass index (BMI), skinfold thickness (subscapular, abdominal and triceps), mid-upper arm and thigh circumference, fat mass (FM) and lean mass were determined and compared with the data of 71 controls.

RESULTS

Girls with AN had lower anthropometric traits and were fat depleted compared to controls (14.9 ± 7.3 vs. 27.4 ± 6.4% of FM using DXA; all p < 0.001). BMI, thigh circumference and subscapular skinfold thickness demonstrated a very similar predictive value for DXA assessment of body fat. Based on the receiver-operating characteristic curve analysis and the determination of the positive predictive value, thigh circumference appeared the most specific and sensitive anthropometric predictor of fatness discriminating between AN and healthy girls, with the AUC value reaching 0.95 (95% CI = 0.92-0.97). Using a cutoff value of 49.6 cm, accuracy was 90.6%, sensitivity 93% and specificity 88.7%.

CONCLUSIONS

Thigh circumference strongly correlates with DXA-FM and demonstrates a slight clinical advantage over BMI. This simple measurement might also serve as a useful predictor of body fatness in adolescent girls with AN and should therefore be further evaluated in independent cohort studies.

Anorexia nervosa and nutritional assessment: contribution of body composition measurements

The psychiatric condition of patients suffering from anorexia nervosa (AN) is affected by their nutritional status. An optimal assessment of the nutritional status of patients is fundamental in understanding the relationship between malnutrition and the psychological symptoms. The present review evaluates some of the available methods for measuring body composition in patients with AN. We searched literature in Medline using several key terms relevant to the present review in order to identify papers. Only articles in English or French were reviewed. A brief description is provided for each body composition technique, with its applicability in AN as well as its limitation. All methods of measuring body composition are not yet validated and/or feasible in patients with AN. The present review article proposes a practical approach for selecting the most appropriate methods depending on the setting, (i.e. clinical v. research) and the goal of the assessment (initial v. follow-up) in order to have a more personalised treatment for patients suffering from AN.

Effect of hydroxyurea on physical fitness indices in children with sickle cell anemia

The current studies aimed at determining physical fitness indices and anthropometrics profiles of children with sickle cell anemia (SCA) after the use of hydroxyurea (HU). Ninety-three male schoolchildren--who participated previously in a similar study before the introduction of HU--comprising 2 groups participated in the studies. Group 1 was 41 children who were suffering from sickle cell disease (SCD) and were on HU for a minimum of 2 years, whereas group 2 was 50 normal healthy controls. Anthropometrics measurement and parameters of physical fitness were assessed in all subjects. All children were also subjected to a minimum of 6-minute running exercise test on a flat motorized treadmill at speed corresponding to 5 km/h. Throughout the test heart rate was monitored and recorded during exercise and for 10 minutes during recovery. Blood hemoglobin (Hb) and HbF% were measured after the use of HU. The mean values of weight, height, and lean body mass were still lower in the SCD children (P < .05) compared with the healthy subjects. However, they had significant decrease in the mean heart rate values and they spent longer time on the treadmill before they got tired compared to their previous performance and were just below the normal controls. Hydroxyurea treatment improved the aerobic exercise tolerance and most of the physical fitness parameters in children with SCD.

Accuracy of a digital skinfold system for measuring skinfold thickness and estimating body fat

The use of skinfold thickness measurements to evaluate the distribution of subcutaneous adipose tissue and to predict body fat has recognised advantages. However, the different types of skinfold calliper available present limitations that make them unattractive and perhaps less used in daily practice. The purpose of the present study was to evaluate the accuracy and functionality of a new digital skinfold system, the Liposoft 2008+Adipsmeter V0 (LA), for measuring skinfold thickness and determining body fat proportion (%BF). Skinfold thickness measurements made by the LA were compared with those obtained with a Harpenden (H) calliper from two samples of adults (n 45) and older adults (n 56) in a university-based cross-sectional study. A comparison was also conducted between estimated %BF from skinfolds and dual-energy X-ray absorptiometry. Bland and Altman plots show that skinfolds measured by the LA and H calliper are in high agreement, with a mean difference of 0·3 (95% CI -3·1, 3·4) mm. In regard to the %BF estimated from LA and H skinfolds measurement, the LA produced a similar approximation to dual-energy X-ray absorptiometry %BF, with a mean difference of 0·2 (95% CI -0·8, 1·2) %, compared with %BF obtained with the H calliper. The LA system is an accurate instrumentation and represents an innovation in the evaluation of skinfold thickness and body composition based on anthropometric measurement.

Accuracy of Siri and Brozek equations in the percent body fat estimation in older adults

OBJECTIVE

To identify which equation, Siri or Brozek, based on the two compartment model, provides a more accurate conversion of body density (BD) in percent body fat (%BF) in a group of older adults.

STUDY DESIGN

Cross-sectional study.

SETTING

Research Centre in Physical Activity, Health and Leisure, Faculty of Sport, University of Porto.

PARTICIPANTS

60 older adults, aged 60-92 years.

MEASUREMENTS

Skinfold thickness was used to estimate BD through Visser et al. prediction equation. The conversion of BD to %BF was done with Siri (%BF-Siri) and Brozek (%BF-Brozek) formulas and these determined values were both compared to Dual-Energy X-ray Absorptiometry (%BF-DXA) evaluations.

RESULTS

A strong correlation between the %BF-DXA value and %BF-Siri (r=0.91, p < 0.001) and %BF-Brozek (r=0.91, p < 0.001) was found, although %BF-Siri and %BF-Brozek overestimated %BF-DXA (p < 0.001). The comparison of the %BF-Siri and %BF-Brozek mean values also revealed significant differences (p < 0.001). The %BF-Brozek reflects a better agreement than the %BF-Siri with %BF-DXA with respectively a mean difference of -4.0 %BF (limits of agreement = -10.9 to 2.9%) and -5.7 %BF (-12.6 to 1.2). The Bland and Altman plots confirmed that %BF-Brozek reflects a better agreement with %BF-DXA.

CONCLUSION

The results of the present study show that the use of Brozek equation may correspond to a more accurate alternative than Siri equation for the conversion of BD in %BF in older adults.

Body composition in severe refractory asthma: comparison with COPD patients and healthy smokers

Background

Body composition is an important parameter for patients with chronic obstructive pulmonary disease (COPD) whereas the association between asthma and obesity is not fully understood. The impact of severe refractory asthma (SRA) on fat free mass (FFM) has not been investigated.

Methodology and Principal Findings

213 subjects (70 healthy smokers, 71 COPD patients and 72 asthma patients) without significant comorbidities were included in the study. In all patients, body composition assessment (using bioelectrical impendance analysis, skinfold and anthropometric measurements) and spirometry were performed. Differences in fat free mass index (FFMI) between groups were assessed and determinants of FFMI in asthma were evaluated. Patients with SRA had lower values of FFMI compared to patients with mild-to-moderate asthma [18.0(17.3–18.3)–19.5(18.4–21.5), p<0.001], despite the fact that they were more obese. The levels of FFMI in SRA were lower than those of GOLD stage I–III COPD and comparable to those of stage IV COPD patients [18.0(17.3–18.3)–18.8(17.8–20.1), p = ns]. These differences were present even after proper adjustments for sex, age, smoking status, daily dose of inhaled corticosteroids (ICS) and daily use of oral corticosteroids (OCS). In multivariate analysis, independent predictors of FFMI in asthmatic patients were age, use of OCS and the presence of SRA, but not smoking, sex or cumulative dose of ICS used.

Conclusions and Significance

SRA is related to the presence of low FFMI that is comparable to that of GOLD stage IV COPD. The impact of this observation on asthma mechanisms and outcomes should be further investigated in large prospective studies.

Comparação entre a adiposidade subcutânea dos hemicorpos direito e esquerdo

O objetivo deste estudo foi comparar os níveis de adiposidade subcutânea dos hemicorpos direito e esquerdo e, posteriormente, analisar o impacto dessas informações para o estudo da composição corporal. Setenta e seis indivíduos fisicamente ativos, 47 homens (21,6 ± 4,3 anos) e 29 mulheres (21,0 ± 2,6 anos), fizeram parte da amostra. As espessuras das dobras cutâneas abdominal, suprailíaca, subescapular, tricipital, bicipital, axilar média e perna medial foram mensuradas com um compasso Lange. Em valores médios absolutos, as maiores diferenças verificadas foram de 0,9mm (6,9%) e 0,8mm (6,8%), na dobra cutânea suprailíaca de homens e mulheres, respectivamente. Entretanto, nenhuma diferença estatisticamente significante foi encontrada na comparação entre os lados, em ambos os sexos, nas sete dobras cutâneas analisadas (P > 0,05). Similarmente, quando os valores medidos foram aplicados em equações preditivas para a determinação da gordura corporal relativa, de acordo com o sexo, nenhuma diferença significante foi encontrada (P > 0,05). Os resultados sugerem que fatores como o erro técnico de medida do avaliador, o tipo de compasso e a escolha da equação preditiva a ser utilizada, provavelmente tenham maior impacto para a estimativa da composição corporal pelo método de espessura de dobras cutâneas do que o lado a ser adotado como referência para a obtenção das medidas.

Estimates of body composition with dual-energy X-ray absorptiometry in adults

BACKGROUND

Little is known about the distributions of percentage body fat (PBF), total body fat (TBF), and fat-free mass (FFM) in the adult population in the United States.

OBJECTIVES

We sought to estimate the means and percentile cutoffs of PBF, TBF, and FFM and to assess the differences by sex, age, race-ethnicity, and body mass index in US adults.

DESIGN

Data from the National Health and Nutrition Examination Survey (NHANES), which were collected during the 6-y period from 1999 to 2004 and comprise a large nationally representative sample of the US population, were analyzed (n = 6559 men and 6507 nonpregnant women). TBF and FFM were measured by using dual-energy X-ray absorptiometry. PBF was calculated as TBF divided by total mass multiplied by 100.

RESULTS

There were large differences between men and women in unadjusted mean PBF (28.1% compared with 40.0%, P < 0.001), TBF (25.4 compared with 30.8 kg, P < 0.001), and FFM (62.3 compared with 44.0 kg, P < 0.001); the sex differences persisted across all body mass index categories after adjustment for age and race-ethnicity (all P < 0.001). The common percentile cutoffs of PBF, TBF, and FFM were estimated by sex, race-ethnicity, and age groups. Equations for the estimation of PBF (R(2) = 0.85), TBF (R(2) = 0.94), and FFM (R(2) = 0.94) according to demographic characteristics and simple anthropometric measures were generated.

CONCLUSION

The estimates of means and percentile cutoffs for PBF, TBF, and FFM, on the basis of NHANES 1999-2004 dual-energy X-ray absorptiometry data, provide a reference in the US adult population.

Body mass index and body fat among adult Bengalee male slum dwellers in West Bengal, India

SUMMARY

OBJECTIVE

The objective of the study is to explore the relationship between body mass index (BMI) and percent body fat (PBF) in relation to hypertension among adult Bengalee males of low socio-economic status living in a slum area of West Bengal, India.

METHODS

A cross-sectional survey was carried on 436 males aged 18-60 years in a slum area called Bidhan Colony, which is approximately 15 km from Kolkata city. Data on anthropometric measurements and blood pressure were collected, following standard techniques. Logistic regression and receiver operating characteristic (ROC) curve analysis were used for testing the relationship between BMI and PBF relative to hypertension.

RESULTS

About 4.25% and 50% of the normal (BMI 18.5-22.9 kg/m(2)) and overweight (BMI 23.0-24.9 kg/m(2)) subjects, respectively, were obese according to the PBF cut-off point of >25%. The ROC curve analysis indicated that the BMI cut-off ≥23 kg/m(2) was appropriate for detecting obesity relative to hypertension. It was observed that the prevalence of hypertension increased significantly with age (r = 0.226, p < 0.001). Adjusting for age, the subjects with BMI 23-24.99 kg/m(2) had about 3.2 times (95% CI: 1.61-6.27) greater risk of hypertension than those with BMI < 23 kg/m(2), and the risk for those with BMI ≥ 25 kg/m(2) was about 4.5 times (95% CI: 2.06-9.57). As for PBF, the risk of hypertension was about 2.6 times (95% CI: 1.38-4.80) for the subjects with PBF > 25% compared to those with PBF ≤ 25%.

CONCLUSIONS

Our study validated the BMI cut-off point proposed by the WHO for Asia-Pacific populations for screening the individuals who are likely at risk of overweight. However, such data should be substantiated by independent risks of adverse health outcomes that need for public health intervention.

Cross-validation of generalised body composition equations with diverse young men and women: the Training Intervention and Genetics of Exercise Response (TIGER) Study

Generalised skinfold equations developed in the 1970s are commonly used to estimate laboratory-measured percentage fat (BF%). The equations were developed on predominately white individuals using Siri's two-component percentage fat equation (BF%-GEN). We cross-validated the Jackson-Pollock (JP) generalised equations with samples of young white, Hispanic and African-American men and women using dual-energy X-ray absorptiometry (DXA) as the BF% referent criterion (BF%-DXA). The cross-sectional sample included 1129 women and men (aged 17-35 years). The correlations between BF%-GEN and BF%-DXA were 0.85 for women and 0.93 for men. Analysis of measurement error showed that BF%-GEN underestimated BF%-DXA of men and women by 1.3 and 3.0 %. General linear models (GLM) confirmed that BF%-GEN systematically underestimated BF%-DXA of Hispanic men and women, and overestimated BF%-DXA of African-American men. GLM were used to estimate BF%-DXA from the JP sum of skinfolds and to account for race/ethnic group bias. The fit statistics (R and standard error of the estimate; see) of the men's calibration model were: white, R 0.92, see 3.0 %; Hispanic, R 0.91, see 3.0 %; African-American, R 0.95, see 2.6 %. The women's statistics were: white and African-American, R 0.86, see 3.8 %; Hispanic, R 0.83, see 3.4 %. These results showed that BF%-GEN and BF%-DXA were highly correlated, but the error analyses documented that the generalised equations lacked accuracy when applied to these racially and ethnically diverse men and women. The inaccuracy was linked to the body composition and race/ethnic differences between these Training Intervention and Genetics of Exercise Response (TIGER) study subjects and the men and women used to develop the generalised equations in the 1970s and using BF%-DXA as the referent criterion.

A comparative study of methods for diagnosis of obesity in an urban mixed-race population in Minas Gerais, Brazil

Background

Obesity is defined as an excess of total body fat and may be assessed by different methods. The objective of the present study was to establish the discriminatory power of anthropometric data in determining obesity.

Methods

The subjects comprised 685 individuals, aged 20–79 years, sampled from a population-based survey. The following indicators were used: body mass index (BMI), waist circumference (WC) and total body fat percentage estimated with both Siri's equation (%BF Siri) and foot-to-foot bioelectrical impedance analysis (%BF BIA). Sensitivity and specificity of different cut-off points for each method were determined using %BF BIA as reference.

Results

Of 685 participants, 57.6% were aged ≥ 40 years, 69.9% were women and 72.6% self-referred themselves as non-white. To classify obesity based on sex and age among women aged < 40 years, the cut-off points were BMI of 26.0 kg m− 2, WC of 84.0 cm and %BF Siri of 34.0%; in those aged ≥ 40 years, the cut-off points were 28.0 kg m− 2, 90.0 cm and 37.4%, respectively. The cut-off points among men aged < 40 years were BMI of 26.3 kg m− 2, WC of 86.0 cm and %BF Siri of 22.5%, and in those aged ≥ 40 years, 26.3 kg m− 2, 89.0 cm and 24.5%, respectively. BMI was the method with the largest area under the curve (AUC) independent of sex and sex/age, yet no differences were observed in AUC between BMI and WC (P>0.05). Classifying according to skin colour did not change cut-off points in any indicator.

Conclusion

BMI and WC better discriminate obesity among women and men aged ≥ 40 years from a mixed-race population.

BMI and morbidity in relation to body composition: a cross-sectional study of a rural community in North-East India

This paper deals with BMI and morbidity in relation to body-fat mass (BFM) and fat-free mass (FFM). The analysis was based on cross-sectional data concerning the age, household income, anthropometry and morbidity of 575 males aged 18–59 years from a rural community in North-East India. Data on morbidity were based on the self-reported morbidity (SRM) of the subjects during the last 4 weeks before the survey, whereas data on BMI and body composition were estimated from anthropometry. It was found that SRM was significantly associated with age and income. However, the relationship between BMI and SRM was not significant after adjusting for age and income. Separating the BMI into body-fat mass index (BFMI being BFM in kg divided by height squared in metres) and fat-free mass index (FFMI being FFM in kg divided by height squared in metres), it was found that BFMI was significantly associated with SRM after adjusting for age, income and FFMI. The subjects with a low (<2·9 kg/m2) BFMI were about 4·7 times (odds ratio 4·7, 95 % CI 2·6, 8·6) more likely to become sick than those with a normal (2·9–5·0 kg/m2) BFMI. In addition, the risk of becoming sick was higher in the subjects with a high (>5·0 kg/m2) BFMI than in those with a normal BFMI (odds ratio 3·9, 95 % CI 1·3, 9·8). However, the relationship between FFMI and morbidity was not clearly perceptible. It is therefore speculated that BMI may not always provide accurate information about the variation in body fat and body composition that is associated with morbidity.

Correlation between high risk obesity groups and low socioeconomic status in school children

OBJECTIVE

Obesity is a major health problem among children and adolescents which is potentially affected by socioeconomic status (SES). The high risk group (HRG) comprises those youths with a body mass index (BMI) between the 85th and 95th percentile (at risk for overweight) and > or = 95th percentile (overweight). We sought a potential link between the HRG and SES.

METHODS

Public schools in Chesterfield County, Virginia measured BMI among students in kindergarten and third, seventh, and tenth grades. We assessed SES based on eligibility for the National School Lunch Program and the percentage of the school-age population living in poverty based on per capita income from the 2000 Census.

RESULTS

From 28 to 38% of children and adolescents were in the high risk group. Low SES had robust and highly significant correlations with HRG status with r-values ranging from 0.565 to 0.842, P < 0.0001.

CONCLUSIONS

Low SES appears to be an important factor in childhood and adolescent obesity.

Physical fitness indices and anthropometrics profiles in schoolchildren with sickle cell trait/disease

The current studies aimed at determining physical fitness indices and anthropometrics profiles of school children with sickle cell trait (SCT) and sickle cell disease (SCD). Male school children (150) comprising 3 Groups participated in the studies. Group 1 has 50 normal healthy controls, while Groups 2 and 3 each has 50 children who were suffering from SCT and SCD, respectively. Anthropometrics measurement and parameters of physical fitness were assessed in all subjects. All children were also subjected to a 5-min running exercise test on a flat motorized treadmill at speed corresponding to 5 km/hr. Throughout the test, heart rate was monitored and recorded during exercise and for 10-min during recovery. Blood lactate was measured before and 5 min following the completion of test. The mean values of lean body mass and height were lower in the SCD children (P < 0.05) compared with the healthy subjects and SCT individuals. Children with SCD exhibited a higher mean value (P < 0.05) for percent body fat and fat mass than the normal healthy subjects and SCT individuals. Although all groups tolerated well the treadmill exercise protocol, the SCD group exhibited higher (P < 0.05) mean values of heart rate during exercise than those observed in the SCT and normal control children. In addition, SCD children showed higher serum lactate values before and after treadmill exercise compared to the other groups. Children with SCD exhibit high level of adiposity; low level of fitness and their exercise performance appears to be physiologically more stressful as indicated by heart rate and blood lactate concentration responses.

Anthropometric evaluations of body composition of undergraduate students at the University of La Reunion

A positive correlation is well established between obesity and the susceptibility to develop metabolic syndrome, a multifactorial disease dramatically associated with an enhanced mortality risk in the developed world. A high prevalence of obesity has recently been described at La Réunion Island, a French department in the Indian Ocean. Anthropometry is generally considered as the single most easily obtainable, inexpensive, and noninvasive method that reflects body composition. At the University of La Réunion, a laboratory course involving students was designed to teach anthropometric measurements for the determination of body composition. Using skin fold thickness equations, students determined the fat and total muscular masses of their body composition. The influences of sex and their physical activity or inactivity on these different parameters were compared and interpreted at the end of the course. Positive and significant correlations were established between the students' body mass indexes values and their fat mass percentages and between their fat-free and muscular masses as well. A higher fat mass percentage was found in sedentary students compared with more active ones. Therefore, this laboratory makes the students practice and understand the use of classical techniques to evaluate the body composition of a person. It also alerts them to the correlation between a sedentary attitude and higher body fat content. This laboratory course constitutes an active introduction to a following lesson on more recent and actual techniques used to evaluate body composition.

Evaluation of Body Fat Changes during Weight Loss by Using Improved Anthropometric Predictive Equations

BACKGROUND/AIM

Skinfold-based equations are widely used to evaluate body fat (BF), but over-/underestimation is often reported. We evaluate the capacity of improved skinfold-based equations to estimate BF changes during weight reduction and compare them against well-established equations.

METHODS

Overweight adults (n = 44) participated in a 4-month weight reduction intervention. Dual-energy X-ray absorptiometry (DXA) and anthropometric measurements were taken at baseline and after intervention. The BF% was calculated using García, Peterson, and Durnin and Womersley (DW) equations.

RESULTS

Baseline and postintervention BF% measured by DXA correlated highest with BF% predicted according to García (r = 0.934 and r = 0.948, respectively), followed by Peterson (r = 0.941 and r = 0.932, respectively) and DW (r = 0.557 and r = 0.402, respectively); only a slight systematic error in overestimating the BF% was observed in estimates according to García (r = 0.147 and r = 0.104, respectively; p < 0.001), while increasing errors occurred using the Peterson (r = 0.624 and r = 0.712, respectively; p < 0.001) and DW (r = 0.767 and r = 0.769, respectively; p < 0.001) equations. Moderate correlations between BF changes (kg) measured by DXA and predicted by DW (r = 0.7211), Peterson (r = 0.697), and García (r = 0.645) were observed.

CONCLUSION

Improved skinfold equations cannot accurately measure changes in BF after weight reduction.

Aplicabilidade de equações na avaliação da composição corporal da população brasileira

O excesso de gordura corporal está, freqüentemente, associado a alterações metabólicas importantes e às doenças crônicas, como diabetes, hipertensão arterial e dislipidemias. A disponibilidade de métodos que permitam estimar a composição corporal é fundamental para avaliação de atletas e do estado de saúde de indivíduos. Entre os métodos existentes, as medidas de dobras cutâneas são habitualmente utilizadas na população brasileira, devido à sua facilidade e relativa precisão em estimar a gordura corporal. Entretanto, existem limitações quanto à utilização desse método, que podem implicar em erros de estimativas da gordura corporal importantes. A proposta deste trabalho é descrever os estudos que validaram essas equações e os principais fatores que influenciam a acurácia das mesmas na população em geral. Também são discutidos aspectos quanto à aplicabilidade dessas equações na população brasileira.

Skinfold prediction equation for athletes developed using a four-component model

INTRODUCTION

Skinfold (SKF) equations exist to predict percent body fat (%BF) in athletes; however, none have been derived from multicomponent model reference measures.

PURPOSE

To develop and cross-validate a %BF prediction equation based on SKF in athletes using a four-component model as the reference measure.

METHODS

Subjects were 132 collegiate athletes (20.7 +/- 2.0 yr; 78 males: 28 black, 50 white; 54 females: 10 black, 44 white). Four-component model estimates of %BF (%BF4C) included measures of total body water from deuterium dilution, bone mineral by dual- energy x-ray absorptiometry (DXA), and body density by densitometry using underwater weighing. SKF measures included subscapular, triceps, chest, midaxillary, suprailiac, abdominal, and thigh sites (7SKF). A prediction equation was developed on 102 athletes using 7SKF, race, and gender as predictor variables. Cross-validation was performed on a representative holdout sample of 30 athletes.

RESULTS

The equation cross-validated well (slope and intercept both not different (P > 0.05) from the line of identity (LOI); r(YY') = 0.85, total error (TE) = 3.76%BF) and was better than the existing athlete SKF equations (intercept and slope both different from LOI (P < 0.01); r(YY') = 0.76, TE = 4.51%BF). Notably, a prediction equation developed using 3SKF sites (abdomen, thigh, and triceps) produced a similar accuracy (intercept and slope both not different from LOI (P > 0.05); r(YY') = 0.85, TE = 3.66%BF).

CONCLUSIONS

The new 7SKF equation improved on SKF equations developed using densitometry. The final equation based on the whole sample was %BF' = 10.566 + 0.12077*(7SKF) - 8.057*(gender) - 2.545*(race). Moreover, a 3SKF equation was comparable in accuracy to the 7SKF equation: BF' = 8.997 + 0.24658*(3SKF) - 6.343*(gender) - 1.998*(race).

Impact of a Home-Based Activity and Dietary Intervention in People With Slowly Progressive Neuromuscular Diseases

OBJECTIVE

To determine whether a home-based activity and dietary intervention can increase activity level, reduce caloric intake, and impact positively components of metabolic syndrome in a disabled population.

DESIGN

Testing occurred at 3 points during the 6-month intervention period (baseline, 3mo, 6mo) and at 6 months postintervention. Each test point included laboratory testing of anthropometric and metabolic variables and 3 days of home-based activity and dietary monitoring. A personally tailored activity and dietary prescription based on baseline testing was implemented during the 6-month intervention period.

SETTING

Human performance laboratory of a university and each subject's home.

PARTICIPANTS

Twenty adult volunteer ambulatory subjects with several types of slowly progressive neuromuscular disease (NMD).

INTERVENTION

Using a pedometer, subjects were instructed to increase number of steps by 25% over their baseline determined from home monitoring. An individualized dietary prescription was provided focusing on problematic issues identified from the baseline dietary profile.

MAIN OUTCOME MEASURES

Body composition, physical activity, dietary intake, energy expenditure, gait efficiency, metabolic variables, and quality of life.

RESULTS

At the end of the protocol, mean step count increased approximately 27% above baseline (P=.001) and caloric intake decreased over 300kcal/d (P=.002). Body fat percentage significantly decreased (from 33.3%+/-1.5% to 32.6%+/-1.6%, P=.032). Gait efficiency did not change, and metabolic variables did not show statistically significant improvement, although 2 of the 5 subjects originally meeting the criteria for metabolic syndrome at baseline no longer met the criteria at the end of the intervention period. Six months after completing the protocol, caloric intake remained significantly reduced (P=.02), but although mean step count remained elevated, it was not statistically significant.

CONCLUSIONS

Using a home-based protocol, people with NMD can increase activity and reduce caloric intake. Although this 6-month program showed positive changes, it was insufficient to affect risk factors associated with metabolic syndrome. It remains to be seen if a program longer than 6 months or a more rigorous program could lead to a reduction in the risk factors associated with metabolic syndrome.

Desenvolvimento e validação de equações antropométricas específicas para a determinação da densidade corporal de mulheres militares do Exército Brasileiro

Este estudo teve por objetivo desenvolver e validar equações específicas para a determinação da densidade corporal de mulheres militares do Exército Brasileiro, com idade entre 18 e 45 anos, servindo na cidade do Rio de Janeiro, a partir de variáveis antropométricas. Para tanto, participaram deste estudo 100 mulheres militares que foram divididas em dois grupos: o grupo de regressão (n = 80), utilizado para o desenvolvimento das equações, e o grupo de validação (n = 20), para validação das mesmas. Foram realizadas as medidas de 10 dobras cutâneas, 10 perímetros, três diâmetros, massa corporal (MC), estatura e densidade corporal (D) através do método da pesagem hidrostática. Para o desenvolvimento das equações, foi realizada a análise de regressão Stepwise e, para sua validação, foram realizados os cálculos do coeficiente de correlação linear de Pearson (p < 0,05), teste t de Student para comparação entre médias (p < 0,05), cálculo do erro constante (EC), cálculo do erro técnico (ET) e erro padrão da estimativa (EPE). Os sujeitos apresentaram as características descritas a seguir: grupo de regressão, com idade de 30,54 ± 6,53 anos, estatura de 165,05 ± 5,95cm, MC de 58,71 ± 6,68kg e D de 1,045620 ± 0,00876g/ml; grupo de validação, com idade de 31,08 ± 6,84 anos, estatura de 164,21 ± 5,49cm, MC de 58,88 ± 7,88kg e D de 1,043877 ± 0,01117g/ml. Após a análise de regressão e seguindo os critérios de escolha, foram desenvolvidas 10 equações, com R entre 0,681 e 0,822 e EPE entre 0,00516 e 0,00652g/ml. As equações foram validadas(1,2) utilizando como variáveis dobras cutâneas, perímetros e diâmetros, sendo destinadas a estimar a D de mulheres militares do Exército, com idade entre 18 e 45 anos.