The body mass index applicability in the body fat assessment

Abstract

Introduction: The body mass index (BMI) is widely used by health professionals in the nutritional status and risk of mortality assessment. However, this index does not provide information about the distribution and proportion of body fat. Objective: To assess BMI efficiency in identifying individuals with surplus body fat and abdominal obesity. Methods: The sample consisted of 98 males between 20 and 58 years of age. The anthropometrical evaluation included weight, height, waist (WC) and hip circumferences. Body composition was evaluated by tetrapolar electric bioimpedance. Results: The sample was predominantly young, having 50% of its individuals aged between 20 and 29 years. Overweight (BMI ≥ 25kg/m2) and abdominal obesity (CC ≥ 94 cm) were found in 36.7% and 18.4% of the evaluated males, respectively. Waist circumference showed the strongest correlation with BMI (r=0.884; p<0.01) and with body fat percentage (r=0.779; p<0.01). BMI sensitivity to diagnose individuals with high waist circumferences, waist-to-hip ratio (WHR) and body fat percentage was 94.4%, 100% and 86.6, respectively, showing its suitability for population studies in order to identify individuals with abdominal obesity and/or surplus body fat. However, BMI was not suitable for this same diagnosis individually, due to the low positive predictive values found: 47.2% for WC, 11.1% for WHR and 36.1% for body fat percentage. Age ≥ 30 years was considered a risk factor for overweight, abdominal obesity and surplus body fat. Conclusions: The importance of combining BMI and WC for verifying adult male nutritional status is emphasized, since abdominal obesity was also found in individuals who were not diagnosed with obesity by BMI.