Measuring Adiposity in Patients: The Utility of Body Mass Index (BMI), Percent Body Fat, and Leptin

Background: Obesity is a serious disease that is associated with an increased risk of diabetes, hypertension, heart disease, stroke, and cancer, among other diseases. The United States Centers for Disease Control and Prevention (CDC) estimates a 20 % obesity rate in the 50 states, with 12 states having rates of over 30%. Currently, the body mass index (BMI) is most commonly used to determine adiposity. However, BMI presents as an inaccurate obesity classification method that underestimates the epidemic and contributes to failed treatment. In this study, we examine the effectiveness of precise biomarkers and duel-energy x-ray absorptiometry (DXA) to help diagnose and treat obesity. Methodology/Principal Findings: A cross-sectional study of adults with BMI, DXA, fasting leptin and insulin results wer

Is the current BMI obesity classification appropriate for black and white postmenopausal women?

OBJECTIVE: To evaluate the relation between body fatness (%Fat) and body mass index (BMI) and to evaluate the validity of the BMI standards for obesity established by the NIH in older black and white postmenopausal women. RESEARCH METHODS: Height, weight, BMI, and %Fat, assessed by DXA, were determined for 296 healthy, independently living women ranging in age from 50 to 80 years (M+/-s.d.; 64.4+/-7.8 years). RESULTS: Per NIH guidelines, 32% were classified as obese (> or = 30 kg/m2, mean BMI = 28.1+/-5.5 kg/m2). In contrast, using the %Fat criterion of 38% advocated by Lohman to define obesity, 47% of our sample was obese (mean %Fat=37.3+/-6.2%). A moderately high curvilinear relation existed between BMI and %Fat (R = 0.82, SEE = 3.57 %Fat, P or = 38 as the criterion for obesity, receiver operating characteristic (ROC) analysis, performed separately by race, indicated that the currently accepted BMI cutpoint for obesity produced low sensitivity (69% and 61% for black and white women, respectively). Alternatively, BMI values > or = 28.4 kg/m2 for black women and > or = 26.9 kg/m2 for white women to define obesity maximized classification accuracy. CONCLUSION: We conclude that current BMI categories may not be appropriate for identifying obesity among postmenopausal women. Furthermore, the relation between BMI and %Fat is different in black compared to white women but remains constant from the sixth through the eighth decade of lif

Sensitivity and specificity of the body mass index for the diagnosis of overweight/obesity in elderly Sensibilidade e especificidade do índice de massa corporal no diagnóstico de sobrepeso/obesidade em idosos

The aim of this article was to verify the sensitivity and specificity of the body mass index (BMI) cut-off points proposed by the World Health Organization (WHO) and the Nutrition Screening Initiative (NSI) for the diagnosis of obesity in the elderly. A cross-sectional study was made with 180 healthy elderly subjects from Florianópolis, Santa Catarina State, Brazil. Body fat percentage (%BF) was determined using DEXA (dual energy X-ray absorptiometry). The BMI cut-off point of the NSI offers better sensitivity and specificity for men (73.7% and 72.5% respectively). For women, the lower the cut-off point the better the sensitivity, with a BMI of 25kg/m² (sensitivity of 76.3% and specificity of 100%) being the most accurate for diagnosing obesity in elderly women. The WHO cut-off point offered very low sensitivity (28.9%). The results of this investigation lead to the conclusion that the cut-off points proposed by the WHO and the ones adopted by the NSI and by Lipschitz are not good indicators of obesity for the elderly of either sex, since they offer low sensitivity.<br>O objetivo foi verificar a sensibilidade e especificidade dos pontos de corte do índice de massa corporal (IMC) propostos pela Organização Mundial da Saúde (OMS) e Nutrition Screening Initiative (NSI) no diagnóstico da obesidade em idosos. O estudo foi realizado com 180 idosos de Florianópolis, Santa Catarina, Brasil. O percentual de gordura corporal foi mensurado por absortometria radiológica de dupla energia. O IMC da NSI apresenta melhores valores de sensibilidade e especificidade para homens (73,7% e 72,5% respectivamente). Para os homens o IMC de 25kg/m² apresentou elevada sensibilidade (94,7%) e baixa especificidade (40%), enquanto o IMC de 30kg/m² possui baixa sensibilidade (31,6%) e elevada especificidade (97,5%). Nas mulheres, o IMC de 25kg/m² (sensibilidade de 76,3% e especificidade de 100%) foi o mais acurado. O ponto de corte da OMS mostrou sensibilidade muito baixa (28,9%). Os resultados desta investigação permitem concluir que os pontos de corte propostos pela OMS e NSI não são bons indicadores de sobrepeso/obesidade para idosos de ambos os sexos