Research Article: Obesity measured as percent body fat, relationship with body mass index, and percentile curves for Mexican pediatric population

Date Published: February 25, 2019

Publisher: Public Library of Science

Author(s): Paula Costa-Urrutia, Alejandra Vizuet-Gámez, Miryam Ramirez-Alcántara, Miguel Ángel Guillen-González, Oscar Medina-Contreras, Mariana Valdes-Moreno, Claudette Musalem-Younes, Jaqueline Solares-Tlapechco, Julio Granados, Valentina Franco-Trecu, M. Eunice Rodriguez-Arellano, Massimiliano Ruscica.


In Mexico, the increase in childhood obesity is alarming. Thus, improving the precision of its diagnosis is expected to impact on disease prevention. We estimated obesity prevalence by bioimpedance–based percent body fat (%BF) and body mass index (BMI) in 1061 girls and 1121 boys, from 3 to 17 years old. Multiple regressions and area under receiver operating curves (AUC) were used to determine the predictive value of BMI on %BF and percentile curves were constructed. Overall obesity prevalence estimated by %BF was 43.7%, and by BMI it was 20.1%; it means that the diagnosis by BMI underestimated around 50% of children diagnosed with obesity by %BF (≥30% for girls, ≥25% for boys). The fat mass excess is further underestimated in boys than in girls when using the standard BMI classification. The relationship between %BF and BMI was strong in school children and adolescents (all cases R2>0.70), but not in preschool children (girls R2 = 0.57, boys R2 = 0.23). AUCs showed greater discriminative power of BMI to detect %BF obesity in school children and adolescents (all cases AUC≥0.90) than in preschool children (girls AUC = 0.86; boys AUC = 0.70). Growth percentile charts showed that girls aged 9–17 years and boys aged 8–17 years presented fat excess from the 50th percentile and above. We suggested to change the BMI cut-off for them, considering values at the 75th percentile as overweight, and values at the 85th percentile as obesity, as previously recommended for Mexican children. Improving obesity diagnosis will allow greater efficiency when searching for comorbidities in clinical practice.

Partial Text

Childhood obesity is the result of an increase in body weight greater than expected with respect to height, which generates excessive body fat. This excess of body fat in children and adolescents can lead to a variety of clinical conditions such as type 2 diabetes (T2D) [1], cardiovascular disease [2], sleep apnea and non-alcoholic fatty liver, which contribute to an increase in morbidity and/or premature mortality [3].

We used anthropometric data of children and adolescents between 3 and 17 years old from COIPIS cohort (Childhood obesity cohort of the Healthy childhood project) of the Genomic Medicine Laboratory at Regional Hospital Lic. Adolfo López Mateos of the Institute of Security and Social Services of State workers (ISSSTE). COIPIS cohort started in 2012 in response to the need for establishing a prospective childhood obesity epidemiologic study. The sample consisted of 1061 girls and 1121 boys, from 3 to 17 years old. Participants were invited among ISSSTE right-holder teachers who were also members of the union, and patients treated at ISSSTE clinics distributed in Mexico City. Participants were examined every 6 months, since they were recruited until they turned 17 years old.

This study included 2,182 children aged between 3 and 17 years (girls = 1,061, boys = 1,121). Descriptive results as mean, standard deviation, coefficient of variation and Box-Cox transformation parameter (L) by sex and age are shown in S1 Table.

In this study, we estimated the obesity prevalence through %BF and BMI, evaluated the relationship between %BF and BMI, and constructed %BF and BMI percentile curves in 2182 Mexican children from 3 to 17 years old.




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