Dual x-ray absorptiometry, bioelectrical impedance, and near infrared interactance in obese women

PURPOSE: Whether the evaluation of body composition in obese people using low-cost, simple bedside, two-compartment techniques reflects the data obtained by indirect methods such as dual x-ray absorptiometry (DEXA) remains controversial. The aim of this study was to compare the data obtained by three methods of assessment of body composition (DEXA; bioelectrical impedance, BIA; and near infrared interactance, NII). METHOD: Data on body composition obtained in 53 obese women by these three methods were compared, using the Bland and Altman procedure to test the relative validity. RESULTS: Although the correlation coefficients between DEXA and the two other methods were high, there were some major differences (limits of agreement) between data concerning fat and lean mass. CONCLUSIONS: The present study indicates that these methods cannot be considered as interchangeable and raises some questions on the use of BIA and NII as a single method of evaluation of body composition in clinical research and practice in obese populations.     

Validity of leg-to-leg bioelectrical impedance measurement in males

BACKGROUND: This study determined the validity of the leg-to-leg bioelectrical impedance analysis (BIA) system (Tanita Body Fat Analyzer, TBF 105, Tanita Corporation of America, Inc., Arlington Heights, IL) in estimating body composition in males. METHODS: EXPERIMENTAL DESIGN: Fat-free mass (FFM) was estimated using BIA and underwater weighing, and compared. SETTING: Subjects were recruited from the community. PARTICIPANTS: Heterogeneous group of males (N=192) was recruited, with a mean+/-SD age of 39.0+/-16.8 yrs; body mass index, 26.0+/-4.0 kg/m2, percent body fat, 18.1+/-8.9 percent. MEASURES: Prior to BIA testing, subjects were required to adhere to standard BIA testing guidelines, and bioelectrical impedance was measured in subjects standing erect with bare feet on the analyzer's footpads, and wearing a swimsuit. Underwater weighing was conducted using standard procedures, with direct measurement of residual volume. RESULTS: A Bland-Altman plot of difference between FFM measured by underwater weighing and BIA versus average FFM by the two methods showed no systematic difference (mean difference, 0.07+/-3.5 kg). FFM was estimated at 66.3+/-8.6 kg with underwater weighing, and 66.2+/-7.7 kg with BIA (r=0.92, p<0.001; SEE 3.5 kg). CONCLUSIONS: These data indicate that the leg-to-leg bioelectrical impedance system accurately assesses FFM in a heterogenous group of males when compared to underwater weighing.     

Body composition in dancers: the bioelectrical impedance method

PURPOSE: The aim of this study was to generate and validate a prediction equation for estimating the body composition in dancers using the bioelectrical impedance analysis (BIA) as a method of assessment. METHODS: The fat-free mass (FFM) of 42 young female professional dance students was estimated by four different methods: dual x-ray absorptiometry (DXA), BIA, simple anthropometry, and skinfold thickness; DXA was used as a criterion method. RESULTS: The dancers' FFM was 42.6 kg (SD: 3.3) and, on the average, body fat represented the 19.4% (SD: 4.3) of their body weight. Two dancer-specific BIA equations for the prediction of FFM (E(BIA)) were developed by multiple regression analysis using weight, height, resistance index, and triceps as predictor variables (E(BIA) and E(BIA-TRICEPS)). The validity of these equations as well as of those previously reported was assessed in two randomly selected subgroups of the initial study group, as described by the Bland-Altman analysis. The bias and the limits of agreement of the equations developed in the present study were lower than those resulting from the application of the previously used equations of Segal et al. and Hergenroeder et al. It was also found that, when validated against DXA, skinfolds measurements did not accurately predict body fatness in this group of young females. CONCLUSION: The new equations allow for an accurate routine assessment of body composition in young female dancers by using the method of BIA. Further studies are needed for the cross-validation of the equations in various groups of dancers.     

Estimation accuracy of percent total body fat and percent segmental fat measured by single-frequency bioelectrical impedance analysis with 8 electrodes: the effect of difference in adiposity

AIM: This study aimed to compare the accuracy of percent total body fat (%TBF) and percent segmental fat (%SF) measurements of new automatic single-frequency bioelectrical impedance analysis with 8 electrodes (SF-BIA8), referenced to the dual-energy X-ray absorptiometry (DXA), between different fatness level female groups. METHODS: Subjects were 34 overweight females (OWG) and 24 normal females (NG). This study used the BIA analyzer of Tanita BC-118 which is a commercially available single frequency bioelectrical impedance analysis system with 8 tactile electrodes. RESULTS: Test-retest reliability in each method was high (intra-class correlations > or =0.96). The SF-BIA8 tends to overestimate %TBF and %SF in the lower extremities and trunk compared with DXA, and consistency with DXA was especially low in %SFs in the lower extremities (left leg: r=0.475, SEE=4.673, right leg: r=0.494, SEE=4.772). Systematic errors regarding to the difference in fatness were found in %TBF and %SFs in lower extremities in OWG, and were found in %SF in upper extremities in NG. Furthermore, systematic errors regarding to the difference in body fat distribution were found in %SFs in lower extremities in OWG, and found in %SFs in upper extremities and trunk in NG. CONCLUSIONS: SF-BIA can provide highly reproducible measurements of %TBF and %SF, but systematic errors based on the differences in fatness and body fat distribution were found. An improved prediction equation considering a variety in fat and body fat distribution will be needed in further investigations.     

Validity of bioelectrical impedance equations for estimating fat-free weight in lean males.

The present study examined the validity of bioelectrical impedance (BIA) equations for estimating fat-free weight (FFW) in lean males (X +/- SD = 9.1 +/- 2.2% fat) by comparing the estimates with values obtained from underwater weighing. Sixty-eight Caucasian male volunteers served as subjects. Cross-validation analyses included examination of the constant error (CE), standard error of the estimate (SEE), r, and total error (TE). The results indicated that the equations of Oppliger et al. (16), which resulted in small TE (1.70 kg) and CE (-0.02 kg) values, most accurately estimated FFW. Simple linear regression showed that FFW was more highly correlated with body weight (BW) (r = 0.98, P < 0.0001) and resulted in a lower SEE (1.68 kg) than either height2/resistance (Ht2/R) (r = 0.81, P < 0.0001; SEE = 5.12 kg) or the independent variable (weight x resistance)/height2 [WR/Ht2] utilized by the manufacturer of the BIA analyzer (r = 0.15, P > 0.05; SEE = 8.59 kg). Multiple regression showed that when WR/Ht2, Ht2/R, resistance, body mass index, Ht2, and/or Ht was added to the prediction equation, which utilized BW alone, they accounted for less than 1% additional variance and reduced the SEE by < or = 0.16 kg. The results indicated that BW alone estimated FFW as accurately as any of the BIA equations in lean males.     

A new waist-to-height ratio predicts abdominal adiposity in adults

ABSTRACT

Our aim was to identify the best anthropometric index associated with waist adiposity. The six weight-status indices included body mass index (BMI), waist-to-hip ratio (WHR), waist-to-height ratio (WHTR), and a new waist-by-height^0.5 ratio (WHT.5R). The association between three waist skinfolds and the six anthropometric indices was conducted using ANCOVA, MANCOVA, allometric modelling and non-linear regression. The strongest predictors of waist adiposity were (1^st) WHT.5R, (2^nd) WHTR, (3^rd) waist circumference (WC), (4^th) BMI, (5^th) WHR, and lastly (6^th) a body shape index ABSI = WC/(BMI^2/3 * height^1/2). The allometric and non-linear regression analyses identified the optimal waist-to-height ratio associated with waist adiposity to be (waist * height ^?0.6). The 95% confidence intervals of the height exponents encompassed ?0.5 but excluded ?1.0 assumed by WHTR. Assuming that excess waist adiposity is an important cardiovascular risk factor, we recommend that the new WHT.5R be used to advise people how to maintain a “healthy” weight.     

Physical activity and fat-free and fat mass by bioelectrical impedance in 3853 adults

OBJECTIVE: To determine the effects of regular physical activity on body composition, as measured by bioelectrical impedance analysis (BIA), in a large Caucasian population of healthy subjects between 15 and 64 yr of age, and to observe the cross-sectional changes in body composition with increasing age. DESIGN: Cross-sectional comparison between sedentary and physically active adults (at least 3 h x wk(-1) at moderate or hard intensity level activity) during aging. SUBJECTS: A total of 3853 healthy adults (1036 sedentary and 1019 physically active men, and 1280 sedentary and 518 physically active women) between 15 and 64 yr of age. MEASUREMENTS: Height, weight, body mass index (BMI), and fat-free mass (FFM), fat mass, and % fat mass measured by 50-kHz BIA. Results: Higher weight in older sedentary adults was due to a higher fat mass. In 55- to 64-yr-olds compared with 25- to 34-yr-olds, fat mass was 5.5 kg (P < 0.0001) higher in sedentary and 0.6 kg (P < 0.3) higher in physically active men, and 4.5 kg (P < 0.0001) and 2.0 kg (P < 0.04) higher in sedentary and physically active women, respectively. Physical activity was able to limit fat mass and weight gain in men over 25 yr of age and in women until 54 yr of age. Endurance type physical activity was not associated with increased FFM. For the same BMI, sedentary men and women have < 0.7 kg (P < 0.001) higher fat mass than physically active men and women. CONCLUSION: Therefore, the benefits of physical activity seem to include maintenance or prevention of an increase of BMI that in turn correlates with prevention of a fat mass increase for physically active subjects.     

Breathlessness predicts perceived exertion in young women with mild asthma.

We examined ratings of breathlessness (BRE) as a predictor of perceived exertion (RPE) during incremental cycling at power outputs of 50, 75, and 100 W. Young females (21 yr +/- 1.9) diagnosed with mild asthma (N = 25) were compared with females having normal lung function (N = 25) matched for age, VO2peak, trait anxiety, activity history (7-d recall), and BMI (kg.m-2). Relative oxygen consumption (%VO2peak), blood lactate concentration, VE.VO2(-1), and state anxiety were statistically controlled in hierarchical multiple linear regression analyses. For each group, %VO2peak explained 60% of the variance in RPE across power outputs (P less than 0.001); R2 was unchanged (P greater than 0.10) with the addition of blood lactate, VE.VO2(-1), and state anxiety. Absolute RPE and BRE did not differ between groups at any power output, but partial standardized (beta) and unstandardized (b) regression coefficients and increases in R2 showed that BRE had a greater effect (P less than 0.01) on RPE for asthmatics [adjusted R2 increased to 0.89; (beta) = 0.75; (b) = 0.79 +/- 0.06] than for controls [adjusted R2 increased to 0.74; (beta) = 0.52; (b) = 0.51 +/- 0.09]. The standard error of the prediction was 0.79 for asthmatics and 1.16 for controls. The prediction of RPE by BRE was not moderated by variation in forced expiratory volume for 1 s (FEV1), forced vital capacity (FVC) or peak inspiratory flow (VI). Physiological responses were similar for the groups, but blood lactate was higher in asthmatics at rest, at each power output, and at VO2peak.(ABSTRACT TRUNCATED AT 250 WORDS)     

Validity of foot-to-foot bioelectrical impedance analysis in overweight and obese children and parents

AIM: The aim of this study was to evaluate the validity of foot-to-foot bioelectrical impedance analysis (FF-BIA) in the measurement of body composition in overweight and obese children and their parents by comparison to dual-energy X-ray absorptiometry (DXA). METHODS: Seventeen, 7-12 year old overweight and obese children (6 boys, 11 girls) and 17 parents (5 fathers, 12 mothers) were evaluated for body composition with FF-BIA and DXA. Measures of percent body fat (PBF), fat mass (FM) and fat free mass (FFM) derived from FF-BIA and DXA were compared. Measures of validity were determined by Pearson correlations between FF-BIA and DXA, paired t-tests to assess mean differences, as well as biases and limits of agreement using the Bland Altman tests. RESULTS: FF-BIA produced estimates of body composition that were highly correlated with DXA in overweight and obese children and parents. For children, the correlations for PBF, FM, and FFM were 0.85, 0.97, and 0.94, respectively. For parents, the correlations for PBF, FM, and FFM were 0.92, 0.97, and 0.91, respectively. However, mean differences between FF-BIA and DXA were significant in children but not in parents. Bland-Altman tests of agreement showed moderate to large within-subject differences in body composition variables between FF-BIA and DXA. CONCLUSIONS: FF-BIA is strongly related to DXA in the measurement of body composition in both overweight and obese preadolescent children and parents, but the two measures may not be used interchangeably. Although FF-BIA may lack the precision to assess small changes in body composition in overweight and obese individuals, it is appropriate for epidemiological use.     

Estimation of body fat in athletes: skinfolds vs bioelectrical impedance

AIM: The aim of the present study was to compare two different field methods (skinfolds(SKF(vs bioimpedance analysis(BIA) for estimation of body fatness in top-level athletes. METHODS: This study was conducted with 219 male professional athletes who were recruited during pre-participation physical examination. Skinfold thicknesses at 7 sites were obtained using a Harpenden caliper while total body resistance was measured with a foot-pad bioelectrical impedance analyzer at a fixed signal frequency of 50 kHz and 500 microA. RESULTS: The athletes showed non-significant difference in body fat percentage (%BF) between the average %BFSKF and %BFBIA (P > 0.05). Average time of assessment per subject was significantly longer during skinfold measurement (P < 0.01) as compared with BIA assessment. CONCLUSIONS: We found that the estimates of body fat were similar between SKF and BIA with significant correlation (r = 0.96) between methods while BIA method is less time-consuming. In conclusion, the most simple, quick, and inexpensive method of BIA seems to be very useful to the dietitians' routine for assessing body fat in physically active individuals and athletes.     

应用生物电阻抗法测量与分析士兵人体成分

 目的 测量士兵人体成分,为确定正常值提供基础数据.方法 对3844名士兵(17～32岁,平均21.6±2.7岁)的身高、体重进行测量,计算体质指数(BMI);应用BFA-100人体脂肪分析仪,测量其生物电阻抗(Ω)、瘦体重(kg)、瘦体百分比、体脂重(kg)、体脂百分比.对不同年龄、不同藉贯、不同等级、不同职务士兵人体成分组成状况进行比较.结果 3844名士兵身高(172.7±4.3)cm、体重(65.7±6.7)kg、BMI(22.1±2.3)、瘦体百分比(81.0±4.0)、体脂百分比(19.0±4.0).不同年龄组的体重、BMI、生物电阻抗、瘦体重、瘦体百分比、体脂重、体脂百分比差异有统计学意义.不同藉贯士兵所有测量数据均无明显差异.不同等级士兵的身高、体重、BMI、瘦体百分比、体脂重、体脂百分比差异有统计学意义.不同职务士兵的体重、瘦体重、瘦体百分比、体脂重、体脂百分比差异有统计学意义.结论 应用生物电阻抗法测量士兵人体成分,对指导部队膳食营养、军事训练,以及确定士兵人体成分正常标准具有重要意义.     

Physical fitness predicts adiposity longitudinal changes over childhood and adolescence

ObjectivesThe purpose of this study was to examine the influence of physical fitness (PF) on the development of subcutaneous adipose tissue in children followed longitudinally over a 9 year period ranging from childhood to adolescence.DesignThis longitudinal study followed 518 healthy participants (262 boys, 256 girls) over a 9-year period ranging from childhood (age 6) to adolescence (age 15). Adiposity (triceps and subscapular skinfolds), and fitness (60 s sit-ups, flexed arm hang, standing long jump, 50 m dash, 10 m shuttle run, sit-and-reach, and 20 m pacer run) were assessed at four annual time points during primary school, and on a follow up, 6 years later, during secondary school.MethodsGrowth in subcutaneous fat was modeled within a HLM statistical framework, using fitness components as time changing predictors.ResultsFlexed arm hang (β = ?0.059; p = 0.000), standing long jump (β = ?0.072; p = 0.000), 60 s sit-ups (β = ?0.041; p = 0.040), 50 m dash (β = 0.956; p = 0.000), and 20 m PACER (β = ?0.077; p = 0.000) tests, were found to predict changes on body fat growth over the years, independently of sex.ConclusionsImproving PF individual levels can positively influence adiposity deposition over the time period covering childhood and adolescence. That occurs independently of the typical sex differentiated adiposity growth.     

Fluid shifts resulting from exercise in rats as detected by bioelectrical impedance

PURPOSE: This study was designed to investigate the immediate effect of exercise intensity and duration on body fluid volumes in rats throughout a 3-wk exercise program. METHODS: Changes in the extracellular water (ECW) and total body water (TBW) volumes of rats were measured preexercise and postexercise using multiple frequency bioelectrical impedance analysis. Groups of rats were exercised at two intensities (6 m.min(-1) and 12 m.min(-1)) for two exercise times (60 min and 90 min) 5 d.wk(-1) during a 3-wk period. Changes in plasma electrolytes, glucose, and lactate resulting from the exercise were also measured on 3 d of each week. RESULTS: Each group of animals showed significant losses in ECW and TBW as a direct result of daily exercise. The magnitude of fluid loss was directly related to the intensity of the exercise, but not to exercise duration; although the magnitude of daily fluid loss at the higher intensity exercise (12 m.min(-1)) decreased as the study progressed, possibly indicating a training effect. CONCLUSION: At low-intensity exercise, there is a small but significant loss in both TBW and ECW fluids, and the magnitude of these losses does not change throughout a 3-wk exercise program. At moderate levels of exercise intensity, there is a greater loss of both TBW and ECW fluids. However, the magnitudes of these losses decrease significantly during the 3-wk exercise program, thus demonstrating a training effect.     

Hydration assessment among marathoners using urine specific gravity and bioelectrical impedance analysis

The present study examined the relationship between urine specific gravity (Usg), body mass (BM) and bioelectrical impedance determined variables [total body water (TBW), per cent TBW and impedance values] before and after a marathon (n = 25 men; 10 women). A significant reduction in BM (pre: 71.2 ± 12.4 kg; post: 69.6 ± 12.0 kg; p < 0.001) and an increase in Usg (pre: 1.009 ± 0.007; post: 1.018 ± 0.009; p < 0.001) was observed post-race. TBW was not significantly decreased (pre: 42.7 ± 8.0 kg; post: 42.4 ± 7.7 kg) while per cent TBW significantly increased post-race (pre: 60.0 ± 3.9%; post: 60.8 ± 3.8%; p < 0.001). Impedance values were significantly greater post-race (pre: 3288 ± 482; post: 3416 ± 492 Ω; p < 0.001). There was no correlation between the change in Usg and the change in BM or any of the bioelectrical impedance determined variables. On average, BM, Usg and impedance values appear to express changes in hydration; however, the observed changes among these variables for a given individual appear to be inconsistent with one another.     

An evaluation of a bioelectrical impedance analyser for the estimation of body fat content.

Measurement of body composition is an important part of any assessment of health or fitness. Hydrostatic weighing is generally accepted as the most reliable method for the measurement of body fat content, but is inconvenient. Electrical impedance analysers have recently been proposed as an alternative to the measurement of skinfold thickness. Both these latter methods are convenient, but give values based on estimates obtained from population studies. This study compared values of body fat content obtained by hydrostatic weighing, skinfold thickness measurement and electrical impedance on 50 (28 women, 22 men) healthy volunteers. Mean(s.e.m.) values obtained by the three methods were: hydrostatic weighing, 20.5(1.2)%; skinfold thickness, 21.8(1.0)%; impedance, 20.8(0.9)%. The results indicate that the correlation between the skinfold method and hydrostatic weighing (0.931) is somewhat higher than that between the impedance method and hydrostatic weighing (0.830). This is, perhaps, not surprising given the fact that the impedance method is based on an estimate of total body water which is then used to calculate body fat content. The skinfold method gives an estimate of body density, and the assumptions involved in the conversion from body density to body fat content are the same for both methods.     

Nonlinear relationships between weekly walking distance and adiposity in 27,596 women

INTRODUCTION/PURPOSE: Data from vigorously active women (runners) suggested that declines in adiposity with weekly running distance were nonlinear and dependent on whether the women are relatively lean or fat. The purpose of the current study is to assess the cross-sectional relationship between the amount of moderate-intensity physical activity (walking distance) and indicators of adiposity. METHODS: Cross-sectional analyses (i.e., quadratic polynomial regression, regression for percentiles of adiposity) of body mass index (BMI), body circumferences, and bra cup sizes in 27,596 women. RESULTS: The estimated percent reductions between walking 40-50 km.wk(-1) and <10 km.wk(-1) were greatest for BMI, intermediate for waist circumference and cup size, and least for hip and chest circumferences. The relationships of walking distance to BMI and body circumferences were all nonlinear (convex). In addition, the inverse relationship between weekly walking distance and adiposity was greatest at the highest percentile of BMI, body circumferences, and cup size, and least at the lowest percentiles. Thus, the decline in adiposity per kilometer per week increment in walking distance was greatest in overweight mostly sedentary women and least in lean active women. The decline in BMI per kilometer per week of exercise was greater in the walkers than previously reported for runners. However, based on the relationships between walking distance and percentiles of the BMI distribution reported here, we show that the majority of this difference is attributable to the leanness of the runners and greater fatness of the walker. CONCLUSION: These data suggest that in women the greatest benefit of walking may be among the most obese and that at higher weekly distances the declines in weight associated with walking diminish. Whether these relationships are causal remains to be determined.     

Body cell mass measured by bioelectrical impedance spectroscopy in professional football (soccer) players

AIM: The aim of this study was to measure body cell mass (BCM) in two football (soccer) teams and assess if there are differences in body composition among players of different field positions. METHODS: Two professional Italian (male) football teams, representing two different divisions (A and C), have been recruited. There were 14 players (4 forwards, 4 defenders, 6 midfielders) in A and 18 players (4 forwards, 4 defenders, 8 midfielders, 2 goalkeepers) in C. Fat free mass (FFM), fat mass (FM), percent body fat (%BF), and BCM have been assessed using bioelectrical impedance spectroscopy (BIS). RESULTS: There were no significant differences in age, body weight, height or body mass index between teams. Team A's BCM was approximately 4 kg greater than C (P=0.001). FFM was significantly greater in midfielders and defenders in A vs C (P=0.02). FFM was significantly lower in forwards compared to defenders within A (P=0.02). Within A, FM and %BF were significantly lower for defenders compared to forwards and midfielders (P=0.01), and BCM was significantly greater in forwards vs defenders (P=0.01), with no significant differences among other field positions. BCM was significantly greater in forwards vs midfielders and defenders within C (P=0.02), with no significant differences between midfielders and defenders. CONCLUSIONS: BCM, measured using BIS, represents an innovative, simple approach to assess body composition. The present study demonstrates that it is very important to analyze body composition in football players, not only with the aim to evaluate the variation of weight in a quantitative and qualitative way, but also with the purpose of selecting players for specific roles. Although these results must be considered not yet conclusive, they could be an important information for coaches, especially during the selection of young football players.     

Energy availability,not body fatness,regulates reproductive function in women

The morbid consequences of menstrual disorders in athletes require medical diagnosis and treatment. Reproductive disruption appears to occur when energy availability (dietary energy intake minus exercise energy expenditure) falls below a threshold between 20 and 30 kcal x kgLBM(-1) x d(-1), and some women may be more severely affected than others by subthreshold energy availability.