Combining Anthropometry and Bioelectrical Impedance to Predict Body Fat in Female Athletes.

CONTEXT Accurate methods for predicting percent body fat in female athletes are needed for those who lose weight for competition. Methods mandated by sports-governing bodies for minimal weight determination in such athletes lack validation. OBJECTIVE To determine whether combining anthropometry (skinfolds, SF) and bioelectrical impedance analysis (BIA) in a 3 component model (3C) would improve the prediction of percentage body fat (%Fat) in female athletes. Secondarily, the Slaughter skinfold equation was evaluated. We hypothesized that compared to outcomes for SF or BIA alone, 3C-determined %Fat would not differ from our criterion method (accuracy) and would be a stronger predictor (higher r2) of the criterion. DESIGN Cross sectional. SETTING Laboratory-based study during the pre-season for collegiate sport. PARTICIPANTS Female athletes (n=18 D1 NCAA) recruited from swim and gymnastic teams. MAIN OUTCOME VARIABLES %Fat based on a four-compartment (4C) criterion incorporating body density (air displacement plethysmography), total body water (D2O dilution), and bone mineral mass (DEXA) compared to predicted %Fat using SF alone (Slaughter equation), bioelectrical impedance analysis (single frequency for TBW estimate) and combined skinfolds and BIA (3C). RESULTS Regression revealed that for %Fat using the criterion 4C, the highest adjusted coefficient of determination and lowest prediction error (r2 ±standard error of estimate) was 3C (r2=0.87 ±2.8%) followed by BIA (r2=0.80 ±3.5%) and SF (r2=0.76 ± 3.8%) (for all, p<0.05). Means differed for %Fat determined using BIA (26.6 ±7.5) and 3C (25.5 ±7.2) vs. the 4C (23.5 ±7.4) (ANOVA and post hoc p<0.05). The SF estimate (24.0 +7.8) did not differ from the 4C value. CONCLUSIONS Combining SF and BIA might improve the prediction and lower the prediction error for determining %Fat in female athletes compared to SF or BIA separately. Regardless, the Slaughter skinfold equation appeared accurate for determining the mean %Fat in these female athletes.