Predicting percentage body fat through waist-to-height ratio (WtHR) in Spanish schoolchildren.

OBJECTIVE: To analyse the association between waist-to-height ratio (WtHR) and body fat and to develop predictive adiposity equations that will simplify the diagnosis of obesity in the paediatric age group. DESIGN: Cross-sectional study conducted in Spain during 2007 and 2008. Anthropometric dimensions were taken according to the International Biology Program. The children were classified as underweight, normal weight, overweight or obese according to national standards of percentage body fat (%BF). WtHR differences among nutritional status categories were evaluated using ANOVA. Correlation analysis and regression analysis were carried out using WtHR as a predictor variable for %BF. A t test was applied to the results obtained by the regression model and by the Siri equation. The degree of agreement between both methods was evaluated by estimating the intra-class correlation coefficient. SETTING: Elementary and secondary schools in Madrid (Spain). SUBJECTS: Girls (n 1158) and boys (n 1161) from 6 to 14 years old. RESULTS: WtHR differed significantly (P < 0.001) depending on nutritional status category. This index was correlated (P < 0.001) with all adiposity indicators. The mean %BF values estimated by the regression model (boys: %BF = 106.50 × WtHR - 28.36; girls: %BF = 89.73 × WtHR - 15.40) did not differ from those obtained by the Siri equation. The intra-class correlation coefficient (0.85 in boys, 0.79 in girls) showed a high degree of concordance between both methods. CONCLUSIONS: WtHR proved to be an effective method for predicting relative adiposity in 6-14-year-olds. The developed equations can help to simplify the diagnosis of obesity in schoolchildren.

Estimación de la adiposidad a partir del índice cintura talla: ecuaciones de predicción aplicables en población infantil española / Adiposity assessment from waist to height ratio: prediction equations for Spanish infant population

Introducción El índice cintura-talla (ICT) es fácil de medir, estable durante el crecimiento y está relacionado con marcadores cardiometabólicos en la infancia y adolescencia. Refleja los depósitos de grasa abdominal y es interesante conocer su relación con la adiposidad total y el porcentaje de grasa. Objetivo Analizar la asociación entre el ICT y la grasa corporal y desarrollar ecuaciones predictivas de la adiposidad que simplifiquen la diagnosis del sobrepeso y la obesidad infantil. Material y Métodos Se han analizado 2319 escolares de ambos sexos entre 6 y 14 años. Se midió el peso (kg), la talla (cm), el perímetro de la cintura (cm) y los pliegues adiposos del bíceps, tríceps, subescapular y suprailíaco (mm). Se calcularon: el índice cintura-talla (ICT) el índice de masa corporal (IMC) y el porcentaje de grasa (% G) por el método de Siri. Los sujetos fueron clasificados en la categoría de normopeso, sobrepeso u obesidad de acuerdo a los estándares de Marrodán et al., evaluando mediante ANOVA las diferencias de ICT entre las tres categorías nutricionales. Se efectuó un análisis de correlación y regresión tomando el ICT como variable predictora de la suma de pliegues y del % G. Se empleó una prueba de T de Student para comparar los variables originales de adiposidad y las predichas por el modelo. Resultados El ICT difiere significativamente (p< 0,001) en función de la categoría nutricional. Este índice se correlacionó significativamente (p < 0,001) en función de la categoría nutricional. Este índice se correlacionó significativamente (p < 0,001) con todos los indicadores de adiposidad aunque los coeficientes “r” fueron más elevados para el contraste con la suma de pliegues (0,823 envarones; 0,821 en mujeres) y el % G (0,811 en varones; 0,793 en mujeres) que con el IMC (0,690 en varones; 0,721 en mujeres). Los valores promedio estimados por el modelo de regresión subestimaron la suma de pliegues ( 0,91 mm en varones; 1,48 mm en mujeres) y resultaron levemente superiores a los de partida en el caso del % G (0,14 mm en varones; 0,31 mm en mujeres). Para la adiposidad relativa, no existen diferencias significativas entre la expresión de Siri y las ecuaciones desarrolladas en el presente trabajo: Varones: % G= 106,50 x ICT- 28,36; Mujeres: %G = 89,73 x ICT -15,40 Conclusiones El índice de cintura-talla (ICT) resulta eficaz para predecir la adiposidad relativa entre los 6 y 14 años. Las ecuaciones desarrolladas contribuyen a simplificar el diagnóstico del sobrepeso y la obesidad en edad pediátrica (AU)

Introduction The waist to height ratio (WHR) is an easy to measure index, stable during growth and related with cardiometabolic markers in childhood and adolescence. WHR reflects abdominal fat deposits, but is interesting to know its relationship with total adiposity and body fat percentage. Objectives The aim of these paper is to analyze the association between WHR and body fat and to develop predictive equations of adiposity in order to simplify the diagnosis of infant overweight and obesity. Material and Methods 2319 schoolchildren of both sexes between 6 and 14 were analized in this study and weight (kg), height (cm), waist circumference (cm) and biceps, triceps, subscapular and suprailiac skinfold thickness (mm) were measured. The waist to height ratio (WHR) body mass index (BMI) and body fat percentage (% BF) by Siri methodology were calculated. Subjects were classified in the category of normal weight, overweight or obesity according to standards of % BF of Marrodán et al. ANOVA test was carried out to evaluate the differences of WHR among the nutritional categories. An analysis of correlation and regression were applied using the WHR as predictor of the sum of skinfold thickness and % BF. We used a Student T test to compare the original variables of adiposity and those predicted by the regression mo del. Results The WHR differs significantly (p <0.001) depending on the nutritional category. This index was significantly correlated (p <0.001) with all indicators of adiposity although the coefficients “r” were higher for the contrast with the sum of skinfolds (0.823 in boys - 0.821 in girls) and % BF (0.811 in boys - 0.793 in girls) than with BMI (0.690- in boys, 0,721 in girls). The average values estimated by the regression model underestimated the sum of skinfolds (0.91 mm in boys and 1.48 mm in girls) and were slightly higher than original values in the case of % BF (0.14 mm in boys and 0.31 mm in girls). For relative adiposity, there is no difference between the expression of Siri and the equations developed in this work: Boys: % BF= 106.50 x 28.36 WHI; Girls: % BF = 89.73 x -15.40 WHI. Conclusions The waist to height ratio (WHR) is effective for predicting relative fatness (% BF) between 6 and 14 years. The developed equations can help to simplify the diagnosis of overweight and obesity in pediatric age (AU)