Desempenho dos índices antropométricos para o diagnóstico de sobrepeso e obesidade em escolares adolescentes

Abstract

Changes in lifestyle and eating habits of the population have resulted in an increase in overweight and obesity and have contributed to the development of several diseases. This clinical condition has become a public health issue in several countries. In this context, anthropometric indicators have been developed to assess the nutritional status of the population. Among them, body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHtR), skinfolds (SF) and conicity index (CI) stand out. Skinfolds show higher specificity for the diagnosis of overweigh/obesity, although they are a more complex measurement. This study aimed to compare anthropometric indices in terms of sensitivity, specificity and accuracy for the diagnosis of overweight/obesity in adolescent students. It is a methodological study using a probabilistic cluster sampling selected by a random draw of schools and classes. Students aged 11 to 14 years old from the selected classes were eligible for the study. Data collection was carried out by a multidisciplinary team previously trained. A questionnaire addressing the socio-demographic characteristics of the adolescents was used. For the anthropometric evaluation, weight, height, waist circumference and tricipital, subscapular and calf skinfolds were measured. BMI, WHtR, CI were calculated and WC was measured. The Body Fat Percentage was calculated through the Slaughter equation, used as the gold standard. The sample was described through the absolute and relative frequency of the variables. In order to assess the predictive capacity, cutoff point, sensitivity and specificity of BMI, WHtR, WC and CI in the identification of the subjects with overweight/obesity, the analysis of the ROC curve was used with 95% confidence intervals and significance level of 5% for each gender. 997 adolescents participated in the study and the prevalence of excess body weight in the population studied was 15.3%, of which 10.6% were overweight and 4.7% obese. Of the four anthropometric indicators studied, BMI, WC and WHtR had the largest areas under the ROC curve for both genders, indicating a good performance in predicting overweight/obesity in adolescents. The cutoff points for males and females, respectively, associated with high body fat were: BMI: 19.7 and 19.4 kg/m2

; WHtR: 0.42 and 0.40; WC: 66 and 61 cm and CI: 1.14 and 1.09. The anthropometric indicators showed greater specificity for the diagnosis of overweight/obesity in both genders, except for WC that showed greater sensitivity 87.0% (95% CI 82.5-90.7) in female. The CI presented the smallest area under the ROC curve and the lowest sensitivity 33.6% (95% CI 27.1-40.8) and 36.8% (95% CI 31.0- 42.9) for males and females, repectively. The importance of using anthropometric indicators is

highlighted, as they are easy to use in screening for overweight/obesity, in addition to showing a frequent association with other diseases that increase morbidity and mortality. Schools have an important educational/social role in nutritional guidance and sports practice, together with health professionals, encouraging students to discuss the benefits of maintaining appropriate weight.