Obesidade e satisfação corporal: um estudo de base populacional em Pelotas, RS

Abstract

Objective To evaluate the accuracy of the Body Mass Index (BMI) calculated through the weight and height self-referred, in predicting the nutritional state of adults and identify factors associated with the classification error. Methods Based on a cross-sectional study with a population including 3934 people older than 20 years old carried out in the city of Pelotas, RS, a subsample of 140 individuals was drawn and measures of weight and height were taken, calculating the BMI with the measures taken and referred. From the comparison between the BMI “measured” the average error of the BMI referred was estimated, identifying the characteristics of the individuals which presented error in the information of the measures. Through the linear regression equation was calculated the “corrected” BMI. The agreement between the “referred” and “corrected” BMIs measured was evaluated by using the Kappa test and the Altman graphic. Results Women, no matter their nutritional state, overestimate the “referred” BMI whereas in men this data was found to be accurate. Among women, age, income, attitude to lose weight and nutritional state were associated with the underestimate of the BMI, in the bivariated analysis, but in the multivariate analysis just the age and familiar income remained. Thus, women over 50 and with lower income underestimated the BMI in more than 2 kg/m². Conclusion The use of the “referred” BMI to predict the nutritional state of adults must be used carefully because it can result in an underestimate of the prevalence of obesity and overestimate of the overweight in women. The correction minimizes this kind of bias making the data accurate.