Methods of Estimation of Visceral Fat: Advantages of Ultrasonography Fernando F. Ribeiro-Filho,* Alessandra N. Faria,* Sergio Azjen,† Maria-Teresa Zanella,* and Sandra R.G. Ferreira‡ Abstract RIBEIRO-FILHO, FERNANDO F., ALESSANDRA N. FARIA, SERGIO AZJEN, MARIA-TERESA ZANELLA, AND SANDRA R.G. FERREIRA. Methods of estimation of visceral fat: advantages of ultrasonography. Obes Res. 2003;11:1488 –1494. Objective: To compare methods for the assessment of vis- ceral fat with computed tomography (CT) and establish cutoffs to define visceral obesity based on such alternative methods. Research Methods and Procedures: One hundred women (50.4 7.7 years; BMI 39.2 5.4 kg/m 2 ) underwent anthropometric evaluation, bioelectrical impedance, DXA, abdominal ultrasonography (US), and CT scan. Results: Waist circumference, waist-to-hip ratio (WHR), and US-determined visceral fat values showed the best correlation coefficients with visceral fat determined by CT (r 0.55, 0.54, and 0.71, respectively; p 0.01). Fat mass determined by DXA was inversely correlated with visceral- to-subcutaneous-fat ratio (r 0.47, p 0.01). Bioimped- ance-determined fat mass and skinfolds were correlated with only subcutaneous abdominal fat quantified by CT. Linear regression indicated US visceral-fat distance and WHR as the main predictors of CT-determined visceral fat (adjusted r 2 0.51, p 0.01). A waist measurement of 107 cm (82.7% specificity, 60.6% sensitivity) and WHR of 0.97 (78.8% specificity, 63.8% sensitivity) were chosen as dis- criminator values corresponding with visceral obesity diag- nosed by CT. A value of 6.90 cm for visceral fat US- determined diagnosed visceral obesity with a specificity of 82.8%, a sensitivity of 69.2%, and a diagnostic concordance of 74% with CT. Discussion: US seemed to be the best alternative method for the assessment of intra-abdominal fat in obese women. Its diagnostic value could be optimized by an anthropometric measurement. Prospective stud- ies are needed to establish CT and US cutoffs for defin- ing visceral-fat levels related to elevated cardiovascular risk. Key words: visceral adiposity, ultrasonography, BMI, circumferences, metabolic syndrome Introduction Obesity is a major public health problem, the prevalence of which has increased worldwide. It is a strong predictor of increased morbidity and mortality (1,2). Since Vague (3) called attention to the importance of adipose tissue distri- bution in 1956, literature has consistently shown associa- tions of upper-body obesity with chronic diseases such as diabetes, hypertension, and cardiovascular disease (4). These and other abnormalities included in the spectrum of metabolic syndrome are linked with insulin resistance (5,6). Visceral adipose-tissue accumulation, through an increased fatty acid production, may be involved in the genesis of insulin resistance (7–9). Therefore, measurements of vis- ceral fat represent an important tool in assessing risk for the metabolic syndrome. Computed tomography (CT) 1 has been considered the most accurate and reproducible technique of body fat mea- surement (10), particularly abdominal adipose tissue. How- ever, CT scans are costly and time-consuming, and involve exposure to ionizing radiation. Because of these limitations, a variety of alternative methods are being used to assess fat distribution and to estimate intra-abdominal fat deposition (11). In addition, ethnicity accounts for different body-fat distribution, limiting the establishment of international stan- Received for review November 19, 2002. Accepted in final form September 22, 2003. *Department of Internal Medicine, Endocrinology Division, †Department of Radiology, and ‡Department of Preventive Medicine, Federal University of Sao Paulo, Sao Paulo, Brazil. Address correspondence to Fernando F. Ribeiro-Filho, Rua Loefgreen, 1543/33-CEP 04040- 032, Sa ˜o Paulo, SP, Brazil. E-mail: [email protected] Copyright © 2003 NAASO 1 Nonstandard abbreviations: CT, computed tomography, US, ultrasonography; BIA, bio- impedance analysis; ROC, receiver operating characteristic; WHR, waist-to-hip ratio. 1488 OBESITY RESEARCH Vol. 11 No. 12 December 2003
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