Techniques of measurement of body composition. Part II

Evaluation of bioelectrical impedance analysis in measuring body fat in 6-to-12-year-old boys compared with air displacement plethysmography

Air displacement plethysmography (ADP) has been considered as the 'standard' method to determine body fat in children due to superior validity and reliability compared with bioelectrical impedance analysis (BIA). However, ADP and BIA are often used interchangeably despite few studies comparing measures of percentage body fat by ADP (%FMADP) with BIA (%FMBIA) in children with and without obesity. The objective of this study was to measure concurrent validity and reliability of %FMADP and %FMBIA in 6-to-12-year-old boys with and without obesity. Seventy-one boys (twenty-five with obesity) underwent body composition assessment. Ten boys participated in intra-day reliability analysis. %FMADP was estimated by Bodpod using sex- and age-specific equations of body density. %FMBIA was estimated by a multi-frequency, hand-to-foot device using child-specific equations based on impedance. Validity was assessed by t tests, correlation coefficients and limits of agreement (LoA); and reliability by technical error of measurement (TEM) and intraclass correlation coefficients (ICC). Compared with %FMADP, %FMBIA was significantly underestimated in the cohort (-3·4 ± 5·6 %; effect size = 0·42) and in both boys with obesity (-5·2 ± 5·5 %; ES = 0·90) and without obesity (-2·4 ± 5·5 %; ES = 0·52). A strong, significant positive correlation was found between %FMADP and %FMBIA (r = 0·80). Across the cohort, LoA were 22·3 %, and no proportional bias was detected. For reliability, TEM were 0·65 % and 0·55 %, and ICC were 0·93 and 0·95 for %FMBIA and %FMADP, respectively. Whilst both %FMADP and %FMBIA are highly reliable methods, considerable differences indicated that the devices cannot be used interchangeably in boys age 6-to-12 years.

Mid-upper arm circumference as a simple tool for identifying central obesity and insulin resistance in type 2 diabetes

BACKGROUND

Our research aimed to explore the correlation between mid-upper arm circumference (MUAC) and central obesity and insulin resistance (IR) in Chinese subjects with type 2 diabetes.

MATERIALS

A total of 103 participants (60 men) were recruited in our study. MUAC was measured around the mid-arm between the shoulder and elbow. Waist circumference (WC) was obtained as central obesity parameter, and the IR parameter of Homeostasis Model Assessment-Insulin Resistance (HOMA-IR) was calculated. The subjects were divided into three groups according to the tertiles cut-points of MUAC level.

RESULTS

Body mass index (BMI), WC, the percentages of central obesity and HOMA-IR were significantly higher in the groups with higher MUAC than those in the group with lower MUAC (all P < 0.05). Pearson analysis showed that MUAC was correlated with BMI, WC, waist-to-hip ratio (WHR), logHOMA-IR, low density lipoprotein cholesterol (LDL-C), uric acid (UA) and high density lipoprotein cholesterol (HDL-C) in all subjects. Multivariate linear regression analysis revealed that MUAC was independently associated with logHOMA-IR (β = 0.036, P<0.001) after adjusting for age, gender, WHR, UA, TG, LDL-C and HDL-C. Binary logistic regression analysis revealed that MUAC was an independent predictor of central obesity (OR: 2.129, 95%CI: 1.311-3.457, P = 0.002). Furthermore, MUAC≥30.9cm for male and ≥30.0cm for female were the optimal cutoff values for identifying central obesity.

CONCLUSIONS

Our study indicated that among Chinese subjects with type 2 diabetes, MUAC is a simple and effective tool for the determination of central obesity and IR. Additionally, the larger MUAC is proved to be more associated with metabolic risk factors of higher UA and LDL-C and lowever HDL-C.

Ultrasound measurements of gastrocnemius muscle thickness in older people with sarcopenia

Background

Sarcopenia, defined as low muscle mass and low muscle strength and/or low physical performance, is affecting more and more people. The European Working Group on Sarcopenia in Older People has suggested the routine community screening. However, selecting the most suitable method to evaluate muscle mass to detect sarcopenia in community screening is a challenge. This study sought to analyze the correlation between ultrasound (US) measurements of the gastrocnemius muscle and low muscle mass, as defined by sarcopenia.

Methods

One hundred thirty-five elderly participants were enrolled. US measurements included muscle thickness (MT), fat thickness (FT), MT/body mass index (BMI), and MT/FT. The definition of low muscle mass was based on the proposal from the Asian Working Group for Sarcopenia, in which the cutoff values for low muscle mass were 7.0 kg/m² for men and 5.4 kg/m² for women using dual energy X-ray absorptiometry (DXA). The participants were divided into low and normal muscle mass groups. Participants with low muscle mass were divided into presarcopenia, sarcopenia, and severe sarcopenia groups.

Results

Those in the low muscle mass group were older and had lower weights and BMIs (P<0.05). In addition, MT and MT/BMI were lower in the low muscle mass group (P<0.05). Binary logistic regression analysis revealed that MT was the factor associated with low skeletal muscle mass (OR =0.001, P<0.001). ANOVA revealed that MT was not significantly different between subjects with presarcopenia, sarcopenia, and severe sarcopenia (F=1.69, P=0.192). Receiver operating characteristic curve analyses indicated that the cutoff value of the gastrocnemius MT for low muscle mass was 1.50 cm.

Conclusion

MT measured by US was identified as the factor associated with low skeletal muscle mass. Those with gastrocnemius MT less than 1.5 cm can be considered as low muscle mass.

Equação de estimativa da composição corporal de idosos do sexo masculino

<p><strong>Objetivo </strong>Desenvolver e validar uma equação de estimativa da composição corporal de homens idosos.</p><p><strong>Metodologia</strong> Correlacional com 85 homens com 69,5±5,8 anos residentes na Grande Vitória, divididos em dois grupos: regressão (n=54) para o desenvolvimento das equações, e validação (n=31). Foram mensurados perímetros (P), dobras cutâneas (DC) e diâmetros ósseos (DO) e o percentual de gordura (%G) determinado pela DXA (Dual X-Ray). As equações foram desenvolvidas por meio da regressão linear múltipla, com validação pelo método <em>stepwise</em>; a comparação das equações foi pelo teste <em>t de</em> <em>Student</em> pareado e a análise dos escores residuais pelo método de Blant e Altman.</p><p><strong>Resultados</strong> O grupo de regressão com 68,5±4,5 anos, massa corporal de 78,5±14,4 kg e 1,6±0,6m; % G de 30,4±6,8 %; o grupo de validação foi de 71,2±7,4 anos, 75,2±11 kg e 1,6±0,5 m e o %G foi 29,4±7,7 %. Foi encontrada a equação G%=23,371+0,337 (P abdomên)–1,464(P antebraço esquerdo)+0,501 (DC panturrilha)+0,175 (massa corporal)–0,741 (DO biacromial)–0,415 (DO bi-iliocristal)+0,374 (P coxa esquerda proximal) + 0,370 (P pescoço). A determinação da reta pelas variáveis foi significativa com o coeficiente de correlação obtido de r=0,8 e o coeficiente de determinação r²=0,8 indicaram que as variáveis dependentes conseguem explicar 87 % da estimativa; O EPE obtido foi igual a 2,6 %.</p><p><strong>Conclusão</strong> A equação resultante foi considerada adequada para a estimativa da gordura corporal de homens com idade superior a 60 anos, podendo ser uma alternativa para o cálculo dessa população. </p>

Morpho-functional response of the elbow extensor muscles to twelve-week self-perceived maximal resistance training

The aim of this study was to determine morphological and functional changes of the elbow extensor muscles in response to a 12-week self-perceived maximal resistance training (MRT). Twenty-one healthy sedentary young men were engaged in elbow extensor training using isoacceleration dynamometry for 12 weeks with a frequency of five sessions per week (five sets of ten maximal voluntarily contractions, 1-min rest period between each set). Prior to, at 6 weeks and after the training, a series of cross-sectional magnetic resonance images of the upper arm were obtained and muscle volumes were calculated. Maximal and endurance strength increased (P<0.01) by 15% and 45% at 6 weeks, and by 29% and 70% after 12 weeks compared with baseline values, while fatigue rate of the elbow extensors decreased by 67%. The volume of triceps brachii increased in both arms (P<0.01) by 4% at 6 weeks, and by 8% after 12 weeks compared with baseline values (right arm--from 487.4 ± 72.8 cm³ to 505.8 ± 72.3 cm³ after 6 weeks and 525.3 ± 73.7 cm³ after 12 weeks; left arm--from 475.3 ± 79.1 cm³ to 493.2 ± 72.7 cm³ after 6 weeks and 511.3 ± 77.0 cm³ after 12 weeks). A high correlation was found between maximal muscle strength and muscle volume prior (r² = 0.62) and after (r² = 0.69) the training (P≤0.05). A self-perceived MRT resulted in an increase in maximal and endurance strength. Morphological adaptation changes of triceps brachii as a result of 12-week specific strength training can explain only up to 26% of strength gain.

Thyroid morphology and function in adults with untreated isolated growth hormone deficiency

OBJECTIVE

GH influences thyroid function and anatomy. Although goiter is frequent in acromegalic patients, the effects of GH deficiency (GHD) are difficult to assess, because hypopituitaric subjects who lack GH often also have a partial or complete deficit of TSH.

STUDY DESIGN

We studied thyroid morphology and serum levels of thyroid hormones in adult members of a large Brazilian kindred with untreated isolated GHD due to a homozygous mutation in the GHRH receptor gene (GHRHR; nine men and 15 women; GHD group) and compared them to subjects heterozygous for the same mutation (eight men and 10 women; HET group) and subjects homozygous for the wild-type allele [seven men and 11 women; control (CO) group].

RESULTS

GHD subjects had a smaller thyroid volume (TV) than HET and CO. The TV of the HET group was intermediate between those of the GHD and CO groups. When TV was corrected by body surface area, it remained smaller in the GHD and HET groups than in the CO group, but the difference between GHD and HET groups disappeared. The GHD group had lower serum T3 levels than the CO group and higher free T4 levels than HET and CO groups.

CONCLUSIONS

Individuals with severe untreated GHD due to a homozygous GHRHR mutation and heterozygous carriers of the same mutation have smaller TV than normal subjects, suggesting that GH has a permissive role in the growth of the thyroid gland. In addition, GHD subjects have reduced serum total T3 and increased serum free T4, suggesting a reduction in the function of the deiodinase system.

Relationships among body composition measures in community-dwelling older women

OBJECTIVE

To examine whether simple anthropometric measures provide a good estimate of total and visceral fat in 146 community-dwelling, older white women (mean age, 74.0 +/- 4.1 years).

RESEARCH METHODS AND PROCEDURES

Total body fat and visceral fat were measured using electron beam computed tomography (EBT). Anthropometric parameters (height, weight, BMI, sagittal diameter, and waist circumference) were measured using standard techniques. Total percentage body fat was assessed using DXA. Spearman correlations were used to examine the association between the measures. Linear regression, controlling for age, was used to examine the associations between the anthropometric parameters and total and visceral body fat measured by EBT.

RESULTS

Correlations among body composition measures ranged from rho = 0.46 to 0.93 (p < 0.0001). EBT total fat was strongly correlated with both DXA estimates of total percentage fat (rho = 0.86) and BMI (rho = 0.89). Separate linear regression models indicated that BMI, waist circumference, sagittal diameter, and DXA total percentage fat were each independently related to EBT total fat. BMI had the strongest linear relationship, explaining 80% of the model variance (p < 0.0001). Linear regression indicated that BMI, waist circumference, and sagittal diameter were each independently related to EBT visceral fat, with BMI and sagittal diameter explaining approximately 53% of the model variance (p < 0.0001).

DISCUSSION

The use of simple anthropometric measures such as BMI, sagittal diameter, and waist circumference may be an appropriate alternative for more expensive techniques when assessing total fat but should be used with caution when estimating visceral body fat.

Prediction and validation of total and regional skeletal muscle mass by ultrasound in Japanese adults

The present study was performed to develop regression-based prediction equations for skeletal muscle (SM) mass by ultrasound and to investigate the validity of these equations in Japanese adults. Seventy-two Japanese men (n=38) and women (n=34) aged 18-61 years participated in this study and were randomly separated into two groups: the model development group (n=48) and the validation group (n=24). The total and regional SM mass were measured using magnetic resonance imaging (MRI) 1.5 T-scanners with spin-echo sequence. Contiguous transverse images (about 150 slices) with a slice thickness of 1 cm were obtained from the first cervical vertebra to the ankle joints. The volume of SM was calculated from the summation of digitized cross-sectional area. The SM volume was converted into mass units (kg) by an assumed SM density of 1.04 kg l(-1). The muscle thickness (MTH) was measured by B-mode ultrasound (5 MHz scanning head) at nine sites on the anatomical SM belly. Strong correlations were observed between the site-matched SM mass (total, arm, trunk body, thigh, and lower leg) by MRI measurement and the MTH x height (in m) in the model development group (r=0.83-0.96 in men, r=0.53-0.91 in women, P<0.05). When the SM mass prediction equations were applied to the validation group, significant correlations were also observed between the MRI-measured and predicted SM mass (P<0.05). The predicted total SM mass for the validation group was 19.6 (6.5) kg and was not significantly different from the MRI-measured SM mass of 20.2 (6.5) kg. Bland-Altman analysis did not indicate a bias in prediction of the total SM mass for the validation group (r=0.00, NS). These results suggested that ultrasound-derived prediction equations are a valid method to predict SM mass and an alternative to MRI measurement in healthy Japanese adults.

Relationship among habitual tea consumption, percent body fat, and body fat distribution

OBJECTIVE

To disclose the possible relationship between habitual tea consumption and changes in total body fat and fat distribution in humans.

RESEARCH METHODS AND PROCEDURES

A cross-sectional survey of 1,210 epidemiologically sampled adults (569 men and 641 women) were enrolled in our study. Tea consumption and other lifestyle characteristics were obtained by structured questionnaires. Percent body fat (BF%) was measured using bioelectrical impedance analysis. Body fat distribution was assessed using waist-to-hip ratio (WHR).

RESULTS

Among the 1,103 analyzed subjects, 473 adults (42.9%) consumed tea once or more per week for at least 6 months. The habitual tea drinkers were male-dominant, more frequently current smokers, and alcohol or coffee drinkers than the nonhabitual tea drinkers. Habitual tea drinkers for more than 10 years showed a 19.6% reduction in BF% and a 2.1% reduction in WHR compared with nonhabitual tea drinkers. The multiple stepwise regression models revealed that men, older age, higher BMI, and current smokers were positive factors for BF% and WHR. In contrast, longer duration of habitual tea consumption and higher total physical activity were negative factors for BF%. Longer duration of habitual tea consumption, higher socioeconomic status, and premenopausal status were negative factors for WHR.

DISCUSSION

An inverse relationship may exist among habitual tea consumption, BF%, and body fat distribution, especially for subjects who have maintained the habit of tea consumption for more than 10 years.

Commonly Used Equations for Estimating Lean Body Weight are Inaccurate

Empiric equations used to estimate lean body weight (LBW) were published in 1974 by Devine. In an attempt to validate these equations, linear regression equations using the 1959 Metropolitan Life Insurance Company (MTL-59) height and weight tables were developed. However, the tables were updated in 1983 (MTL-83) with different weights, with some values as much as 17% higher. This study's purpose was to determine if the regression equations had changed. The results demonstrate that the linear relationship between height and weight is not as strong with the 1983 table values. In addition, two LBW equations indicate that the weight values reported in 1983 overestimate LBW by 7 to 13 kg. These data indicate that the Devine formulas for estimating LBW may in reality be estimating “average” weight for height. A call is made for future studies that test whether estimating LBW according to population-specific formulas leads to a more accurate representation of the clinical pharmacokinetics of drugs.

Estimativa da gordura corporal através de equipamentos de bioimpedância, dobras cutâneas e pesagem hidrostática

A estimativa do percentual de gordura (%G) pela bioimpedância (BIA) tem como vantagem a simplicidade da medida. Contudo, a confiabilidade da BIA tem sofrido críticas. O objetivo deste estudo foi comparar a estimativa do %G através das técnicas de bioimpedância (RJL-101; Byodinamics A-310, Maltron BF-900 e BF-906), de dobras cutâneas (DC) e da pesagem hidrostática (PH). Observaram-se 25 indivíduos, homogeneizados segundo raça (branca), gênero (masculino) e idade (18 a 36 anos). Para a medida de BIA foi utilizada a padronização proposta por Lukaski et al. (1985, 1986). Para as DC foram utilizadas as equações de <FONT FACE=Symbol>å</FONT> 3 DC e <FONT FACE=Symbol>å</FONT> 7 DC (Jackson, Pollock, 1978). Os valores de %G e de volume residual para PH foram preditos, respectivamente, pelas equações de Siri (1961) e Goldman e Becklake (1959). A análise estatística compreendeu: a) comparação entre os métodos através da ANOVA com medidas repetidas seguida de testes post-hoc de Tukey; b) correlação de Pearson (r); e c) cálculo do erro padrão de estimativa (SEE) das técnicas em relação à PH. Os resultados indicaram que: a) as medidas de BIA não diferiram significativamente, entre si, para o %G estimado; b) As medidas dos aparelhos A-310 e BF-906 não coincidiram com a PH (p < 0,01); c) Em geral, os valores de SEE apresentados pela BIA foram altos; d) Os valores de r oscilaram entre 0,35 (RJL-101) e 0,70 (BF-906); e) As técnicas de DC apresentaram correlações maiores e SEE menores com a PH, quando comparados com os da BIA. Apesar dos resultados, não há dados que permitam indicar um aparelho em detrimento de outros. Os resultados da BIA equivaleram-se quanto à estimativa do %G, mas a técnica de DC mostra-se tão ou mais confiável para tanto. Contudo, os resultados devem ser ratificados pela ampliação da amostra e controle de maior número de variáveis intervenientes.

Estimation of body composition in muscular dystrophy by MRI and stereology

We have applied the Cavalieri method of modern design stereology with magnetic resonance imaging for estimating the volume of whole-body muscle and fat compartments in four patients with muscular dystrophy, a patient with myopathy, five controls, an anorexic subject, and a body builder. Detailed systematic series (ie, 50) of axial MR images (T1-weighted, TR/TE 400/10 msec) were obtained throughout the whole body of each subject. The results showed that 15, 20, and 35 axial sections through the body are sufficient to secure coefficients of error (CEs) on the estimates of total muscle and fat volume of around 10%, 5%, and 3% respectively in muscular dystrophy patients and controls. The mean normalized volumes of muscle in four muscular dystrophy patients were decreased by 27% (t-test: P < 0.05), and those of total fat were increased by 12% (t-test: P > 0.05) relative to controls. The Cavalieri method provides a direct, efficient, and mathematically unbiased approach for studying human body compartments and may have application in assessing treatment efficacy in patients with muscular dystrophy. J. Magn. Reson. Imaging 2000;12:467-475.

Serum leptin and body composition in children with familial GH deficiency (GHD) due to a mutation in the growth hormone-releasing hormone (GHRH) receptor

OBJECTIVE

The relationship between GH, body composition and leptin in children remains ill-defined. We have therefore examined the impact of severe GH deficiency (GHD) due to a mutation in the GHRH receptor on serum leptin concentrations and body composition in childhood.

PATIENTS

12 affected children and young people (GHD) (4 M:8F, age 5.4-20.1 years, 8 Tanner stage (TS) 1-2, 4 TS 3-5) and 40 healthy controls (C) from the same region (13 M:27F, age 5.3-18.4 years, 20 TS 1-2, 20 TS 3-5).

METHODS

Percent body fat was determined by infra-red interactance, from which the amounts of fat mass (FM, kg) and fat free mass (FFM, kg) were derived. Serum leptin concentrations were measured in a single fasted, morning serum sample and results expressed as a concentration and as leptin per unit fat mass (L/FM, ng/ml/kg). To control for differences in sex and pubertal maturation, leptin standard deviation scores (leptin SDS) were calculated using normative data from UK children.

RESULTS

FFM was significantly lower in GHD children than in controls (TS 1-2 P < 0.05, TS 3-5 P < 0.001). FM did not differ significantly between the two groups. Serum leptin concentrations, leptin per unit fat mass and leptin SDS were significantly elevated in GHD children both peripubertal and pubertal compared with controls. Using all subjects, stepwise multiple linear regression with FM, FFM, age, puberty and sex as explanatory variables and leptin concentration as the dependent variable indicated that 59% of the variability in leptin could be accounted for by FM (+, 45%), FFM (-, 9%) and sex (+, 5%) (P < 0.001). However on inclusion of GH deficiency (coded GHD = 1, control = 2) as an explanatory variable 73% of the variability in leptin was explained by FM (+, 45%), GHD (-, 22%) and sex (+, 6%) (P < 0.001).

CONCLUSIONS

These data indicate that severe GH deficiency in children is associated with elevated leptin concentrations, irrespective of sex or pubertal stage. This increase is not associated with differences in fat mass but is related to reduced fat free mass in GH deficiency. Furthermore in this population there may be an additional effect of GH deficiency on leptin, independent of the influences of sex and body composition.

A comparison of air displacement plethysmography with three other techniques to determine body fat in healthy adults

BACKGROUND

This study compared air displacement plethysmography (ADP), which relies on measurements of body density to estimate body fat, with three other techniques that measure body composition: (1) hydrostatic weighing (HW), which also measures body density; (2) bioelectrical impedance (BIA), which determines electrical resistance and total body water to estimate fat-free mass; and (3) dual-energy x-ray absorptiometry (DXA), which measures bone, fat, and fat-free soft tissue masses.

METHODS

ADP, HW, BIA, and DXA were performed on 20 healthy volunteers (10 males and 10 females). The subjects were within 20% of ideal body weight, 31.1 +/- 1.8 years of age, and 75.4 +/- 2.7 kg with body mass index values of 25.2 +/- 0.9 (kg/m2) and percent body fat by ADP ranging from 6.0% to 41.0%.

RESULTS

Percent body fat measurements by the four methods were highly correlated (r > .90, p < .0001). Mean body fat as determined by ADP, HW, BIA, and DXA were 23.4% +/- 2.3%, 23.9% +/-1.8%, 23.1% +/- 1.9%, and 26.4% +/- 2.4%, respectively (* p < .05 vs ADP). There was a significantly positive slope (+0.23) for the individual differences vs the average of ADP and HW percent body fat, demonstrating a slightly negative difference at lower body fat levels and a slightly positive difference at greater body fat levels. Although the average percent body fat determined by ADP was similar to that by HW for the entire population, there was a significant gender difference with the average body fat measured by ADP being 16% less in males and 7% greater in females than that determined by HW.

CONCLUSIONS

Body fat measurements using ADP were highly correlated with those using HW, BIA, and DXA across a relatively wide range of body fat levels in healthy adults. These results support the utility of ADP as a relatively new technique in the estimation of percent body fat in healthy adults. However, the error associated with gender and the level of body fat is not negligible and requires further investigation.

Body composition measurement: a review of hydrodensitometry, anthropometry, and impedance methods

Human body composition is an expression of genetic and nutritional factors. It can change as a consequence of exogenous influences such as training, disease, or diet and is therefore of particular interest to nutrition professionals. Two of the main methods of estimating body composition in this review (hydrodensitometry and anthropometry) have been in use for decades, but the third method (bioelectrical impedance) is more recent. The procedure, theoretical basis, assumptions, standard error of estimates, and comparisons with other techniques are presented for each of the three methods. References to general and specific populations are presented that illustrate regression equations for different ages, ethnic groups, and gender. The advantages and disadvantages of the three methods are reviewed with reference made to the alternative compartment models. Other methods (DEXA, infrared interactance) are briefly reviewed.

Serial measurements of body composition in obese subjects during a very-low-energy diet (VLED) comparing bioelectrical impedance with hydrodensitometry

Bioelectrical impedance analysis (BIA) is a convenient, inexpensive, and noninvasive technique for measuring body composition. BIA has been strongly correlated with total body water (TBW) and also has been validated against hydrodensitometry (HD). The accuracy and clinical utility of BIA and HD during periods of substantial weight loss remain controversial. We measured body composition in moderately and severely obese patients serially using both methods during a very-low-energy diet (VLED). Mean initial weight in these patients was 116 (+/-30) kg (range, 74-196 kg). Mean weight loss was 24 (+/-13) kg with a decrease in fat mass (FM) by HD of kg (p < 0.001) and a decrease in fat-free mass (FFM) of 3.6 kg (p < 0.05). Loss of FFM is best predicted by the rate (kg/wk) of weight loss (r2 = 0.86, p < 0.0001). FFM, as predicted from BIA equations, was highly correlated with FFM as estimated by HD during all testing sessions (r = 0.92-0.98). Although highly correlated, BIA overestimated FFM relative to HD and this difference appeared to be more pronounced for taller patients with greater truncal obesity. Although the discrepancy was no greater during weight-loss treatment, the level of disagreement was considerable. Therefore, the two methods cannot be used interchangeably to monitor relative changes in body composition in patients with obesity during treatment with VLED. The discrepancy between BIA and HD may be caused by body mass distribution considerations and by perturbations in TBW which affect the hydration quotient for FFM (BIA) and/or which affect the density constants for FFM and FM (HD).

Salivary monoamine oxidase A and B inhibitory activities correlate with stress

MAO A and B inhibitory activities were determined, for the first time, in saliva samples. Saliva was collected on 4 occasions from 11 normal subjects (students) before and after delivering an important assessed oral presentation, a naturalistic stress inducing procedure. The first sample was collected 30 minutes before the presentation and 3 more within 40 minutes of finishing the presentation. At each collection a mood adjective checklist was completed. Mean MAO A inhibitory activity correlated with mean MAO B inhibitory activity (r = 0.872, p < 0.001, n = 11). Within subject analysis revealed a positive correlation between MAO A and B inhibitory activity and stress (r = 0.400, p < 0.01, n = 44 and r = 0.255, NS, n = 38 respectively). Mean MAO A and B inhibitory activity correlated with mean stress (r = 0.535, NS, n = 11 and r = 0.673, p < 0.05, n = 11 respectively). Peak MAO A and B inhibitory activities correlated with peak stress (r = 0.636, p < 0.05, n = 11 and r = 0.754, p < 0.01, n = 11, respectively). Salivary MAO A and B inhibitory activities were independent of salivary flow rate. We conclude that measurement of MAO A and B inhibitory activities in saliva is preferable to traditional urinary measures as sampling is less invasive and also supports a clear relationship to stress in normal individuals.

Age- and menopause-associated variations in body composition and fat distribution in healthy women as measured by dual-energy X-ray absorptiometry

To assess the variation with age and menopause, 407 healthy normal women aged 18 to 75 years had body composition and fat distribution measured by dual-energy x-ray absorptiometry (DEXA). The mean +/- SD are given for different age decades. Postmenopausal women had significantly more fat, a more central fat distribution, and less lean tissue mass (LTM) than premenopausal women. In premenopausal and postmenopausal women, age only correlated with the abdominal to total-body fat tissue ratio (r approximately .24, P < .05), whereas the years since onset of menopause correlated with fat tissue mass (FTM), fat%, abdominal fat%, and the abdominal to total-body fat tissue ratio (r approximately .2, P < .05). To assess the independent impact of age, menopausal status, and years since menopause, multiple linear regressions were performed. FTM, fat%, and abdominal fat% were significantly related to menopausal status and years since menopause independently of age. The abdominal to total-body fat tissue ratio was statistically significantly related to age, but tended also to be independently related to years since menopause. LTM was statistically significantly related to menopausal status independently of age and years since menopause. In summary, we suggest that in healthy women total-body and abdominal fat may increase and LTM may decrease in the years after menopause, primarily in the perimenopausal years, without significant changes before menopause.

Unbiased estimation of human body composition by the Cavalieri method using magnetic resonance imaging

The classical methods for estimating the volume of human body compartments in vivo (e.g. skin-fold thickness for fat, radioisotope counting for different compartments, etc.) are generally indirect and rely on essentially empirical relationships--hence they are biased to unknown degrees. The advent of modern non-invasive scanning techniques, such as X-ray computed tomography (CT) and magnetic resonance imaging (MRI) is now widening the scope of volume quantification, especially in combination with stereological methods. Apart from its superior soft tissue contrast, MRI enjoys the distinct advantage of not using ionizing radiations. By a proper landmarking and control of the scanner couch, an adult male volunteer was scanned exhaustively into parallel systematic MR 'sections'. Four compartments were defined, namely bone, muscle, organs and fat (which included the skin), and their corresponding volumes were easily and efficiently estimated by the Cavalieri method: the total section area of a compartment times the section interval estimates the volume of the compartment without bias. Formulae and nomograms are given to predict the errors and to optimize the design. To estimate an individual's muscle volume with a 5% coefficient of error, 10 sections and less than 10 min point counting (to estimate the relevant section areas) are required. Bone and fat require about twice as much work. To estimate the mean muscle volume of a population with the same error contribution, from a random sample of six subjects, the workload per subject can be divided by square root of 6, namely 4 min per subject. For a given number of sections planimetry would be as accurate but far more time consuming than point counting.

Muscle performance and gross motor function of children with spastic cerebral palsy

The purpose of this study was to determine whether, and to what extent, performance on a measure of motor function (Gross Motor Function Measure, GMFM) was related to the physiological fitness of children with cerebral palsy (CP). Two elements of physiological function were measured: aerobic power and anaerobic power of the arms and legs. 15 boys and eight girls aged between seven and 13.9 years with spastic CP participated in the study. There was a good relationship between the standing and walking, running and jumping sub-sections and the total score of the GMFM on one hand, and anaerobic capacity of the legs on the other. However, the relationships for the arms were limited, indicating that the GMFM is not a suitable tool for providing information about aerobic fitness in children with CP, or about anaerobic power of the arms.