PERFORMANCE DIAGNÓSTICA DO ÍNDICE DE MASSA CORPORAL NA DETECÇÃO DE OBESIDADE E PONTOS DE CORTE DE INDICADORES DE OBESIDADE PARA PREDIÇÃO DE DESFECHOS CARDIOMETABÓLICOS.

Abstract

Obesity is a recognized risk factor for the development of cardiometabolic outcomes. Thus, it is important to evaluate the anthropometric and body composition indicators used for the diagnosis of obesity. This thesis consists of two articles. In the first, the diagnostic capacity of body mass index (BMI) in the detection of obesity was evaluated according to three different cutoff points for the high percentage of body fat (%BF). This study was carried out with 2,447 adolescents aged 18-19 years of the 1997/98 São Luís cohort and 951 adults aged 21-23 years of the 1994 Ribeirão Preto cohort. The analysis of the area under the ROC curve (AUC) was used to assess BMI performance. The diagnostic capacity of BMI varied according to the cutoff points of the %BF used, with age and sex. The use of higher cutoff points for the %BF resulted in an increase in BMI sensitivity, with a reduction in the number of false negatives. In the second article, the cutoff points for %BF, the fat mass index (FMI) and the BMI are investigated to detect cardiometabolic risk factors. This study included 3,517 adults aged 30 years of the 1982 Pelotas cohort and 1,696 adults aged 37-39 years of the 1978/79 Ribeirão Preto cohort. Analysis of the ROC curve was used to determine the cutoff points for predicting systolic and diastolic blood pressure, blood glucose, triglycerides, total cholesterol, LDL cholesterol, HDL cholesterol, C-reactive protein and glycated hemoglobin. The %BF values ranged from 25.2 to 27.8 in men and from 37.4 to 39.7 in women, at 30 years; and from 26.1 to 27.8 in men and from 38.5 to 42.2 in women, at 37-39 years. For the IMG (kg/m2) the values varied from 6.3 to 7.5 in men and from 9.5 to 10.8 in women, at 30 years; and from 7.3 to 7.8 in men and from 10.2 to 12.2 in women, at 37-39 years. The cutoff values for BMI (kg/m2) ranged from 26.3 to 27.3 in men and from 25.4 to 27.2 in women, at 30 years; and from 28.3 to 29.0 in men and from 27.2 to 29.6 in women, at 37-39 years. The indicators showed close AUC and with low to acceptable discriminatory power. The findings of the studies showed that the use of different references for the classification of high %BF implied differences in the diagnostic capacity of BMI to identify of obesity, and that BMI did not differ from indicators based on body fat to predict most cardiometabolic risk factors.