Body mass index for predicting hyperglycemia and serum lipid changes in Brazilian adolescents

Ana Carolina R Vieira,Rosely Sichieri,Marlene M Alvarez,Salim Kanaan,Gloria V Veiga

doi:10.1590/s0034-89102008005000062

Abstract

OBJECTIVE: To determine the best cut-offs of body mass index for identifying alterations of blood lipids and glucose in adolescents. METHODS: A probabilistic sample including 577 adolescent students aged 12-19 years in 2003 (210 males and 367 females) from state public schools in the city of Niterói, Southeastern Brazil, was studied. The Receiver Operating Characteristic curve was used to identify the best age-adjusted BMI cut-off for predicting high levels of serum total cholesterol (>150mg/dL), LDL-C (>100mg/dL), serum triglycerides (>100mg/dL), plasma glucose (>100mg/dL) and low levels of HDL-C (< 45mg/dL). Four references were used to calculate sensitivity and specificity of BMI cut-offs: one Brazilian, one international and two American. RESULTS: The most prevalent metabolic alterations (>50%) were: high total cholesterol and low HDL-C. BMI predicted high levels of triglycerides in males, high LDL-C in females, and high total cholesterol and the occurrence of three or more metabolic alterations in both males and females (areas under the curve range: 0.59 to 0.67), with low sensitivity (57%-66%) and low specificity (58%-66%). The best BMI cut-offs for this sample (20.3 kg/m² to 21.0 kg/m²) were lower than those proposed in the references studied. CONCLUSIONS: Although BMI values lower than the International cut-offs were better predictor of some metabolic abnormalities in Brazilian adolescents, overall BMI is not a good predictor of these abnormalities in this population.

Highlights

In Brazil, overweight prevalence in adolescents tripled over a period of 20 years[23] with increased risk for cardiovascular diseases resulting from metabolic abnormalities.[19]
The best Body mass index (BMI) cut-offs for this sample (20.3 kg/m2 to 21.0 kg/m2) were lower than those proposed in the references studied
Overweight prevalence was less than 20% and prevalence of high total cholesterol (≥150 mg/dL) and low high-density lipoprotein cholesterol (HDL-C) (

Summary

Introduction

In Brazil, overweight prevalence in adolescents tripled over a period of 20 years[23] with increased risk for cardiovascular diseases resulting from metabolic abnormalities.[19]. Body mass index (BMI) is used to evaluate overweight and obesity It is correlated with body fat, it is measured and can be used for both adolescent and adult evaluation.[14,25] The cut-offs used for definition of overweight and obesity, generally in the 85th and 95th percentiles of the distribution based on American population data,[17,20] were statistically defined, and they are not associated to morbidity or mortality. BMI accuracy for predicting body fat in adolescents has been widely investigated and it has shown better specificity than sensitivity.[4,24] BMI validation depends on its ability of predicting body fat and mostly future risks to health, associated with metabolic changes, such as hyperglycemia, and dyslipidemias

Methods

Results

Conclusion