Abstract
The purpose of this investigation was to determine the validity of 4-compartment (4C) model body fat percent (BF%) estimates when using dual energy x-ray absorptiometry (DXA) derived body volume (BV) equations (4C-DXA1 and 4C-DXA2) in adults with varying body mass index (BMI) and waist circumference (WC) classifications. Each model was compared to a criterion 4C model with air-displacement plethysmography (ADP) generated BV (4C-ADP). Participants were categorized as normal weight (n = 40; NW = BMI<25.0kg/m2); overweight (n = 40; OWBMI = BMI≥25.0 kg/m2); and overweight with at-risk WC (n = 35; OWBMI+WC = BMI≥25.0 kg/m2 and WC≥88.0cm for women and 102.0cm for men). 4C-DXA1 produced lower BF% than that derived using the 4C-ADP in NW (CE = -3.0%; p<0.001) while 4C-DXA2 was significantly higher (CE = 4.8%; p<0.001). The SEE and 95% limits of agreement (LOA) were lower for 4C-DXA2 (1.24% and ±2.5%, respectively) than 4C-DXA1 (2.59% and ±5.0%, respectively) and proportional bias was present for both (p<0.05). 4C-DXA1 BF% was not significant in OWBMI (CE = -0.5%; p = 0.112) whereas 4C-DXA2 was higher (CE = 4.5%; p<0.001). The SEE and 95% LOA were lower for 4C-DXA2 (1.20% and ±2.9%, respectively) than 4C-DXA1 (1.92% and ±3.9%, respectively) in OWBMI. Proportional bias was present for 4C-DXA1 (p = 0.007), but not 4C-DXA2 (p = 0.832). 4C-DXA1 and 4C-DXA2 produced significantly higher BF% in OWBMI+WC (CE = 2.2 and 2.3%, respectively; both p<0.001). The SEE and 95% LOA remained lower for 4C-DXA2 (1.15% and ±2.5%, respectively) than 4C-DXA1 (1.84% and ±3.8%, respectively). There was proportional bias for 4C-DXA2 (p = 0.020), but not 4C-DXA1 (p = 0.183) in OWBMI+WC. Only one prediction model (i.e., 4C-DXA1 in OWBMI+WC) revealed valid estimates of BF%. Practitioners are encouraged to use criteria for both BMI and WC when utilizing DXA-derived BV in 4C-models for normal and overweight populations.
Highlights
Body composition is a fundamental measure for health, fitness, and risk assessment utilized by practitioners and fitness professionals alike
The mean BF% for 4C-DXA1 was significantly lower than that derived using the 4C-air displacement plethysmography (ADP) (CE = -3.0%; p < 0.001) whereas 4C-DXA2 was significantly higher (CE = 4.8%; p < 0.001)
The current study sought to determine the validity of 4C model BF% estimates when using dual-energy x-ray absorptiometry (DXA)-derived body volume (BV) equations in adults with varying body mass index (BMI) and waist circumference (WC) classifications
Summary
Body composition is a fundamental measure for health, fitness, and risk assessment utilized by practitioners and fitness professionals alike. The significance of accurate measures of body composition has led to improvements in the techniques used to quantify and interpret these measurements. From early assessments such as skinfolds and single-frequency bioelectrical impedance analysis (BIA) along with the simpler measures of body mass index (BMI) and waist circumference (WC), several advanced techniques are available. These techniques include body volume (BV) measures via air displacement plethysmography (ADP) or under water weighing (UWW), bone mineral content (BMC) via dual-energy x-ray absorptiometry (DXA), or total body water (TBW) analysis via multi-frequency BIA
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