RESUMEN
BACKGROUND: The body mass index (BMI) is the most commonly used anthropometric indicator. However, it does not discern among the different body components. The body fat content, expressed as fat mass index (FMI), is an accurate way to estimate adiposity. Since most metabolic diseases are associated with excess fat tissue, our aims were to comparatively analyze the frequency of associated metabolic abnormalities in patients with different obesity degrees based on BMI and FMI and to determine the best cut-off value of both indicators to predict metabolic abnormalities. METHODS: From a cohort of 2007 patients, BMI and FMI were calculated using DXA. Individuals were classified into the different obesity degrees according to the reference ranges from the World Health Organization (WHO) and the National Health and Nutrition Examination Survey (NHANES). A comparative analysis between BMI, FMI, and their correlation to the presence of metabolic alterations was performed. RESULTS: BMI underestimated the degree of obesity when compared with FMI. Spearman's rank-order correlation for both indexes resulted in very high coefficients (rho Spearman's = 0.857; p = 0.0001). The prevalence of metabolic alterations increased as BMI and FMI also increased. Despite the high positive statistical correlation between BMI and FMI, it was seen that some comorbidities were more specifically related to one particular index. CONCLUSIONS: There were no significant differences between the BMI and the FMI for predicting the degree of obesity. Likewise, there were no significant differences between them for the prediction of metabolic alterations.
