Inconsistencies in bioelectrical impedance and anthropometric measurements of fat mass in a field study of prepubertal children

The present study examined the consistency of bioelectrical impedance analysis (BIA) and anthropometric measurements in body composition analysis in a field study of prepubertal children using a representative group of 2286 5-7-year-old children from Kiel, north-west Germany. Body composition was assessed using anthropometric measures (A; four skinfolds) and BIA. Various published algorithms (according to Lohmann (1986) and Deurenberg et al. (1990) for A, Kushner et al. (1992), Schaefer et al. (1994) and Wabitsch et al. (1996) for BIA and Goran et al. (1996) for a combined approach) were used to estimate body composition. Using A resulted in a sum of four skinfolds varying between age-dependent median values of 24.0 and 28.2 mm in boys and 30.5 and 33.3 mm in girls. When fat mass (FM) was calculated from A, age- and algorithm-dependent differences in median values were observed, with values varying between 8.5 and 14.6% for boys and 1.11 and 14.9% for girls. Using different algorithms (Lohmann (1986) v. Deurenberg et al. (1990)) only minor inconsistencies were observed. BIA-derived resistance index (height2/resistance) varied between 18.8 and 24.4 cm2/omh for boys and 17.1 and 19.0cm2/ohm for girls. Using four different algorithms to estimate FM from BIA data resulted in high intra-individual variances in percentage FM (from 13.8 to 33.4) as well as in the prevalence of overweight (from 14.7 to 98.4% for boys and from 42.3 to 98.5 % for girls). Data obtained using the different BIA algorithms showed some, or even marked, inconsistencies as well as systematic deviations (an overestimation of FM at low percentage FM, Schaefer et al. (1994) v. Wabitsch et al. (1996)). When comparing BIA with A, BIA systematically overestimated FM. The differences between the results were influenced by BMI, gender and height. Considerable inconsistencies were observed at low BMI (<10th percentile) for girls and for small children. Although the within-observer as well as between-observer CV for both techniques are acceptable, we recommend caution in relation to the algorithms used for data analysis. The use of an interchange table of percentage FM derived from different algorithms for different percentile groups of skinfold thicknesses is recommended.

Homocysteine concentrations in a German cohort of 500 individuals: reference ranges and determinants of plasma levels in healthy children and their parents

Elevated plasma homocysteine is a risk factor for cardiovascular disease and a sensitive marker of inadequate vitamin B12 and folate status. We studied 257 pupils (120 boys, 137 girls, aged 6-17 years) and their parents (88 males, 172 females, aged 26-50 years). Our measurements were part of a national Bavarian health and nutrition examination survey evaluating cardiovascular risk factors. A mild hyperhomocysteinemia (Hcys >15 micromol/l) occurred in 7% of the adults, but in none of the children. Men had significantly higher Hcys levels than women (p<0.0001), boys and girls had comparable concentrations. For adults and children, Hcys correlated inversely with vitamin B12 and folate and positively with the lean body mass and creatinine in serum, but not with cystatin C. Genetic and nutritional factors are determinants of Hcys metabolism. The correlation of Hcys and serum creatinine is dependent on the metabolic link between Hcys production and creatine synthesis.