Estimation of body fatness by air displacement plethysmography in African American and white children

Percentage fat in overweight and obese children: comparison of DXA and air displacement plethysmography

OBJECTIVE

To compare percentage body fat (percentage fat) estimates from DXA and air displacement plethysmography (ADP) in overweight and obese children.

RESEARCH METHODS AND PROCEDURES

Sixty-nine children (49 boys and 20 girls) 14.0+/-1.65 years of age, with a BMI of 31.3+/-5.6 kg/m2 and a percentage fat (DXA) of 42.5+/-8.4%, participated in the study. ADP body fat content was estimated from body density (Db) using equations devised by Siri (ADP(Siri)) and Lohman (ADP(Loh)).

RESULTS

ADP estimates of percentage fat were highly correlated with those of DXA in both male and female subjects (r=0.90 to 0.93, all p<0.001; standard error of estimate=2.50% to 3.39%). Compared with DXA estimates, ADP(Siri) and ADP(Loh) produced significantly (p<0.01) lower estimates of mean body fat content in boys (-2.85% and -4.64%, respectively) and girls (-2.95% and -5.15%, respectively). Agreement between ADP and DXA methods was further examined using the total error and methods of Bland and Altman. Total error ranged from 4.46% to 6.38% in both male and female subjects. The 95% limits of agreement were relatively similar for all percentage fat estimates, ranging from +/-6.73% to +/-7.94%.

DISCUSSION

In this study, conversion of Db using the Siri equation led to mean percentage fat estimates that agreed better with those determined by DXA compared with the Lohman equations. However, relatively high limits of agreement using either equation resulted in percentage fat estimates that were not interchangeable with percentage fat determined by DXA.

Influence of excess adiposity on exercise fitness and performance in overweight children and adolescents

OBJECTIVE

Relatively little is known about how excess body mass affects adolescents' capacity to perform sustained exercise. We hypothesized that most of the difficulty that severely overweight adolescents have with sustained exercise occurs because the metabolic costs of moving excess mass result in use of a high proportion of their total oxygen reserve.

METHODS

We compared results from a maximal cycle ergometry fitness test in 129 severely overweight adolescents who had BMIs of 41.5 +/- 9.7 kg/m2 and ages of 14.5 +/- 1.8 years (range: 12.1-17.8 years) and 34 nonoverweight adolescents who had BMIs of 20.1 +/- 2.9 kg/m2 and ages of 14.5 +/- 1.5 years (range: 12.0-18.1 years). Oxygen uptake (Vo2) was compared at 3 times: during a 4-minute period of unloaded cycling (ULVo2), at the lactate threshold estimated by gas exchange (LTVo2), and at maximal exertion (Vo2 max). Heart rate was obtained at rest and at Vo2 max. Participants also completed a 12-minute walk/run performance test to obtain distance traveled (D12) and heart rate.

RESULTS

Absolute LTVo2 and Vo2 max and LTVo2 as a percentage of Vo2 max were not different in overweight and nonoverweight adolescents during the cycle test. However, absolute ULVo2 was significantly greater in overweight adolescents: ULVo2 accounted for 35 +/- 8% of Vo2 max (and 63 +/- 15% of LTVo2) in overweight adolescents but only 20 +/- 5% of Vo2 max (and 39 +/- 12% of LTVo2) in nonoverweight adolescents. Resting heart rate before initiating the cycle test was significantly greater in overweight than nonoverweight adolescents (94 +/- 14 vs 82 +/- 15 beats per minute). However, maximal heart rate during the cycle test was significantly lower in overweight adolescents (186 +/- 13 vs 196 +/- 11 beats per minute). During the walk/run test, mean D12 was significantly shorter for overweight than for nonoverweight adolescents (1983 +/- 323 vs 1159 +/- 194 m). D12 was negatively related to BMI SDS (r = -0.81) and to ULVo2 (r = -0.98).

DISCUSSION

Overweight and nonoverweight adolescents had similar absolute Vo2 at the lactate threshold and at maximal exertion, suggesting that overweight adolescents are more limited by the increased cardiorespiratory effort required to move their larger body mass through space than by cardiorespiratory deconditioning. The higher percentage of oxygen consumed during submaximal exercise indicates that overweight adolescents are burdened by the metabolic cost of their excess mass. Their greater oxygen demand during an unloaded task predicted poorer performance during sustained exercise. Exercise prescriptions for overweight adolescents should account for the limited exercise tolerance imposed by excess body mass, focusing on activities that keep demands below lactate threshold so that exercise can be sustained.

Comparison of methods to assess change in children's body composition

BACKGROUND

Little is known about how simpler and more available methods to measure change in body fatness compare with criterion methods such as dual-energy X-ray absorptiometry (DXA) in children.

OBJECTIVE

Our objective was to determine the ability of air-displacement plethysmography (ADP) and formulas based on triceps skinfold thickness (TSF) and bioelectrical impedance analysis (BIA) to estimate changes in body fat over time in children.

DESIGN

Eighty-six nonoverweight and overweight boys (n = 34) and girls (n = 52) with an average age of 11.0 +/- 2.4 y underwent ADP, TSF measurement, BIA, and DXA to estimate body fatness at baseline and 1 +/- 0.3 y later. Recent equations were used to estimate percentage body fat by TSF measurement (Dezenberg equation) and by BIA (Suprasongsin and Lewy equations). Percentage body fat estimates by ADP, TSF measurement, and BIA were compared with those by DXA.

RESULTS

All methods were highly correlated with DXA (P < 0.001). No mean bias for estimates of percentage body fat change was found for ADP (Siri equation) compared with DXA for all subjects examined together, and agreement between body fat estimation by ADP and DXA did not vary with race or sex. Magnitude bias was present for ADP relative to DXA (P < 0.01). Estimates of change in percentage body fat were systematically overestimated by BIA equations (1.37 +/- 6.98%; P < 0.001). TSF accounted for only 13% of the variance in percentage body fat change.

CONCLUSION

Compared with DXA, there appears to be no noninvasive and simple method to measure changes in children's percentage body fat accurately and precisely, but ADP performed better than did TSF or BIA. ADP could prove useful for measuring changes in adiposity in children.

Use of air displacement plethysmography in the determination of percentage of fat mass in african american children

The purpose of this study was to determine the ability of air displacement plethysmography (ADP) to estimate percentage of fat mass (%FM) in African American children. %FM was determined in 21 boys and 13 girls (11.0 +/- 1.4 y, 18.6 +/- 4.2 kg/m(2) [mean +/- SD]) by ADP (using six published densitometric equations) and dual-energy x-ray absorptiometry (DXA). Measures were done within 2 h of one another, in random order. Regardless of equation, %FM(ADP) was significantly correlated with %FM(DXA) (R(2) = 0.67-0.71, all p < 0.001). %FM(ADP) using the equation of Siri (%FM(ADP-Siri) 20.3 +/- 9.0) agreed most closely with %FM(DXA) (20.0 +/- 10.2, difference p = 0.729). Together, surface area artifact and bone mineral content per unit of bone-free fat-free mass accounted for 29% of the variance in the residual between methods. The correlation between %FM(ADP-Siri) and %FM(DXA) was not significant for those <35 kg (n = 10; R(2) = 0.084, p = 0.417). There was a trend toward %FM(ADP-Siri) underestimating %FM(DXA) in girls (-1.46 +/- 3.0%FM; p = 0.103) but not in boys (1.43 +/- 6.4%FM; p = 0.315). Predicted lung volume was 40.1% higher than measured lung volume (p < 0.001). %FM(ADP-Siri) determined using predicted lung volume was 23.5 +/- 8.9, higher than that using measured lung volume (p < 0.001) and higher than %FM(DXA) (p = 0.001). We conclude that in 9- to 14-y-old African American children and provided lung volume is measured, %FM using ADP with Siri's equation approximates that obtained by DXA. Body composition results determined by ADP in children <35 kg should be interpreted with caution.

The use of air displacement plethysmography in children and adolescents with cystic fibrosis

OBJECTIVES

The purpose of this paper was to evaluate the use of air displacement plethysmography (ADP) in children and adolescents with cystic fibrosis (CF). Specifically, the primary aim of this study was to compare estimates of fat-free mass (FFM) measured from ADP and dual energy X-ray absorptiometry (DEXA) in children and adolescents with CF. The secondary aim was to compare the effect of using predicted thoracic gas volume (VTG) and measured VTG for the calculation of FFM by ADP in this population.

METHODS

Cross-sectional FFM measurements were taken using ADP and DEXA in 52 children and adolescents with CF, ranging in age from 6.3 to 16.6 y.

RESULTS

Bland-Altman analysis showed that ADP values of FFM were on average 0.59 kg higher than DEXA values (95% limits of agreement = 3.61 to -2.43 kg); however this difference was not significant. There was no significant correlation (r = -0.26, P = 0.07) between the mean FFM and difference in FFM between ADP and DEXA. Using either predicted or measured VTG did not significantly affect FFM estimates in individuals with CF who had normal lung function (bias = -0.39 +/- 0.86 kg; r = -0.02, P = 0.93).

CONCLUSIONS

ADP is an appropriate technique for use in children and adolescents with CF.

Effect of race and musculoskeletal development on the accuracy of air plethysmography

PURPOSE

The purpose of this study was to determine the effect of race and musculoskeletal development on the accuracy of estimates of body fatness (%fat) via air displacement plethysmography (AP).

METHODS

Estimates of %fat were made via AP, hydrostatic weighing (HW), dual-energy x-ray absorptiometry (DXA), and the criterion, a four-component model (4C) in 64 black (B) and white (W) men, who were either resistance trained (RT) or served as controls (C).

RESULTS

Based on a three-way ANOVA, there were no statistically significant three-way or race x musculoskeletal development interactions. There was no main effect of race on the validity of estimating %fat by AP; the mean bias between %FatAP and %Fat4C was similar for B (3.6% body fat) and W (3.7%). In addition, the density of the fat-free mass (Dffm) for B (1.098 +/- 0.002 g x mL) was not different than 1.10 g x mL. There was a significant effect of musculoskeletal development on the validity of the estimation of %fat from AP; the mean difference in %fat between %FatAP and %Fat4C was less in RT (1.5% body fat) than in C (5.3%), but a large SEE of 5.5% was observed for RT. A significant (P < 0.05) correlation was found between the mean bias between methods and body volume (-0.44) and mesomorphy (-0.55).

CONCLUSIONS

Race does not affect the accuracy of estimating %fat by AP. Race-specific equations estimating %fat via densitometry (e.g., AP, HW) such as the Schutte are not justified, because Dffm is not greater than 1.10 g x mL. Estimation of %fat via AP is more accurate in larger individuals with high musculoskeletal development as a group, but individual results are highly variable.

Validation of a new pediatric air-displacement plethysmograph for assessing body composition in infants

BACKGROUND

The accurate measurement of body composition is useful in assessments of infant growth and nutritional status.

OBJECTIVE

This study evaluated the reliability and accuracy of a new air-displacement plethysmography (ADP) system for body-composition assessment in infants.

DESIGN

Between- and within-day reliability was assessed by comparing the percentage body fat (%BF) obtained on consecutive days and on the same day, respectively, in 36 full-term infants. Accuracy was assessed by comparing %BF measured with the use of ADP and %BF measured with the use of deuterium (2H2O) dilution in 53 infants.

RESULTS

There were no significant differences in %BF between days (-0.50 +/- 1.21%BF) or within days (0.16 +/- 1.44%BF). Mean between- and within-day test-retest SDs of 0.69 and 0.72%BF, respectively, indicated excellent reliability. The %BF measurements obtained by using ADP were not significantly influenced by infant behavioral state. Mean %BF obtained by using ADP (20.32%BF) did not differ significantly from that obtained by using 2H2O dilution (20.39%BF), and the regression line [%BF(2H2O) = 0.851%BF (ADP) + 3.094] gave a high R2 (0.76) and a low SEE (3.26). The 95% limits of agreement between ADP and 2H2O (-6.84%BF, 6.71%BF) were narrower than those reported for other body-composition techniques used in infants. Individual differences between the 2 methods were not a function of body mass or fatness.

CONCLUSION

ADP is a reliable and accurate instrument for determining %BF in infants, and it has the potential for use in both research and clinical settings.

Estimates of percentage body fat in young adolescents: a comparison of dual-energy X-ray absorptiometry and air displacement plethysmography

OBJECTIVE

To evaluate the accuracy of percentage body fat (%fat) estimates from air displacement plethysmography (ADP) against an increasingly recognised criterion method, dual-energy X-ray absorptiometry (DXA), in young adolescents.

DESIGN

Cross-sectional evaluation.

SETTING

Leeds General Infirmary, Centre for Bone and Body Composition Research, Leeds, UK.

SUBJECTS

In all, 28 adolescents (12 males and 16 females), age (mean+/-s.d.) 14.9+/-0.5 y, body mass index 21.2+/-2.9 kg/m(2) and body fat (DXA) 24.2+/-10.2% were assessed.

RESULTS

ADP estimates of %fat were highly correlated with those of DXA in both male and female subjects (r=0.84-0.95, all P<0.001; s.e.e.=3.42-3.89%). Mean %fat estimated by ADP using the Siri (1961) equation (ADP(Siri)) produced a nonsignificant overestimation in males (0.67%), and a nonsignificant underestimation in females (1.26%). Mean %fat estimated by ADP using the Lohman (1986) equations (ADP(Loh)) produced a nonsignificant underestimation in males (0.90%) and a significant underestimation in females (3.29%; P<0.01). Agreement between ADP and DXA methods was examined using the total error (TE) and methods of Bland and Altman (1986). Males produced a smaller TE (ADP(Siri) 3.28%; ADP(Loh) 3.49%) than females (ADP(Siri) 3.81%; ADP(Loh) 4.98%). The 95% limits of agreement were relatively similar for all %fat estimates, ranging from +/-6.57 to +/-7.58%. Residual plot analyses, of the individual differences between ADP and DXA, revealed a significant bias associated with increased %fat (DXA), only in girls (P<0.01).

CONCLUSIONS

We conclude that ADP, at present, has unacceptably high limits of agreement compared to a criterion DXA measure. The ease of use, suitability for various populations and cost of ADP warrant further investigation of this method to establish biological variables that may influence the validity of body fat estimates.

Validity of six field and laboratory methods for measurement of body composition in boys

OBJECTIVE

To determine the validity of the following six body composition methods against a reference method (three-component model): air displacement plethysmography (BODPOD); estimation from body density using BODPOD; skinfold thickness using the Slaughter equations; bioelectrical impedance, both leg-leg (TANITA) and hand-foot (Bodystat) approaches; and total body water.

RESEARCH METHODS AND PROCEDURES

Forty-two healthy white 10- to 14-year-old boys (mean age, 12.9 +/- 1.0 years) were enrolled in this study. Measures of body fat percentage and body fat mass derived from the three-component model were used as the reference method. Validity of all of the other methods was assessed by comparison against the reference by calculation of biases and limits of agreement.

RESULTS

Mean body fatness measured using the reference method was 16.4 +/- 11.6% and 8.7 +/- 7.0 kg. Estimates of fatness from total body water had the narrowest limits of agreement relative to the reference (+0.9 +/- 5.0% body fat; +0.5 +/- 2.9 kg fat mass). For all other methods tested, we observed large biases and very wide limits of agreement.

DISCUSSION

This study suggests that the validity of newer field and laboratory methods for estimation of body composition is poor in adolescent boys. For applications where high accuracy of estimation at the individual level is essential, only reference methods would be acceptable.