Validity of bioelectrical impedance analysis in predicting total body water and adiposity among Senegalese school-aged children

Introduction Childhood obesity is currently a serious public health challenge in developing countries. Therefore, an accurate assessment of adiposity is required. The objective of this study was to validate BIA prediction equations for the assessment of total body water and adiposity or percentage of body fat for the first time in Senegalese school-aged children. Methods One-hundred-fifty-one (151) pupils who were 8-11 years old were randomly selected from four public schools in Dakar. The body composition measured by deuterium dilution method (DDM) was used as the reference method and compared to that predicted by BIA using a multi-frequency analyser. Stepwise backward multiple linear regression was performed to calculate TBW and %BF in a subsample, which were then validated in the rest of the sample. The Bland and Altman approach was used to assess the agreement between the two methods (bias and limits of agreement). Results FFM was higher in boys (24.6 +/- 6.9 kg) compared to girls (21.2 +/- 3.3 kg; P<0.001), and FM was lower in boys: 3.7 kg [0.9-26.4] compared to girls: 4.5 kg [1.7-22.7]. Overall, 11.3% of children presented excess adiposity (%BF >25% in boys, and >30% in girls) and 2.0% were obese according to WHO cut points for obesity (BMI z-score >+2.0). The equations developed were as follows: TBW = 0.376(Height(2)/Z(50))-0.470 (sex) +0.076(weight) +0.065 (height)-2.28. %BF = -1.10(height(2)/Z(50)) +3.14(sex)+1.57(weight)-4.347. These specific equations showed good precision and a low and non-significant mean bias (0.11 kg, P = 0.279; and 0.19 kg, P = 0.764) for TBW and %BF, respectively. Conclusion The newly developed equations can be used as an accurate and alternative screening tool for the assessment of obesity among children in various settings.