Surrogate markers of visceral adiposity in young adults: waist circumference and body mass index are more accurate than waist hip ratio, model of adipose distribution and visceral adiposity index

Abstract

Surrogate indexes of visceral adiposity, a major risk factor for metabolic and cardiovascular disorders, are routinely used in clinical practice because objective measurements of visceral adiposity are expensive, may involve exposure to radiation, and their availability is limited. We compared several surrogate indexes of visceral adiposity with ultrasound assessment of subcutaneous and visceral adipose tissue depots in 99 young Caucasian adults, including 20 women without androgen excess, 53 women with polycystic ovary syndrome, and 26 men. Obesity was present in 7, 21, and 7 subjects, respectively. We obtained body mass index (BMI), waist circumference (WC), waist-hip ratio (WHR), model of adipose distribution (MOAD), visceral adiposity index (VAI), and ultrasound measurements of subcutaneous and visceral adipose tissue depots and hepatic steatosis. WC and BMI showed the strongest correlations with ultrasound measurements of visceral adiposity. Only WHR correlated with sex hormones. Linear stepwise regression models including VAI were only slightly stronger than models including BMI or WC in explaining the variability in the insulin sensitivity index (yet BMI and WC had higher individual standardized coefficients of regression), and these models were superior to those including WHR and MOAD. WC showed 0.94 (95% confidence interval 0.88-0.99) and BMI showed 0.91 (0.85-0.98) probability of identifying the presence of hepatic steatosis according to receiver operating characteristic curve analysis. In conclusion, WC and BMI not only the simplest to obtain, but are also the most accurate surrogate markers of visceral adiposity in young adults, and are good indicators of insulin resistance and powerful predictors of the presence of hepatic steatosis.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. Surrogate indexes of visceral adiposity in control women (circles, n = 20), women with polycystic ovary syndrome (PCOS, diamonds, n = 53) and men (squares, n = 26) as a function of obesity (defined as BMI ≧30 kg/m2, white symbols  =  non-obese subjects, black symbols  =  obese individuals).

Data are means ± SEM and were submitted to univariate general linear models introducing groups of subjects and obesity as independent variables and age as a covariate to correct the results for a difference in age among patients with PCOS with the other groups. Obese subjects showed increased total body fat mass values when compared with non-obese individuals (P<0.001 for all indexes with the exception of MOAD, P = 0.011), irrespective of sex and PCOS. P values indicate the differences between control women, women with PCOS and men, irrespective of the presence or absence of obesity. No interaction was found between obesity and groups of subjects in any of the measurements of the indexes of visceral adiposity.

Figure 2. Surrogate indexes of visceral adiposity and BMI depending on the grade of hapatic steatosis as estimated by ultrasound in the 99 subjects included in the study, irrespective of sex, PCOS and obesity.

Hepatic steatosis was graded as follows: grade 0, normal echogenicity; grade 1, slight, diffuse increase in fine echoes in liver parenchyma with normal visualization of diaphragm and intrahepatic vessel borders; grade 2, moderate, diffuse increase in fine echoes with slightly impaired visualization of intrahepatic vessels and diaphragm; grade 3, marked increase in fine echoes with poor or nonvisualization of the intrahepatic vessel borders, diaphragm, and posterior right lobe of the liver. Data are means ± SEM and were submitted univariate general linear models introducing grade of hepatic steatosis as independent variable and age as a covariate. * All comparisons between grades of steatosis showed statistically significant differences with P<0.05 or less. † Values in grades 1, 2 and 3 were similar and higher than those observed in grade 0. ‡ Values in grades 1, 2 and 3 steatosis were higher than those observed in grade 0, and grade 2 steatosis also showed higher values compared with grade 1.

Figure 3. Receiver operating characteristic (ROC) curve analysis of the diagnostic performance of surrogate indexes of visceral adiposity and BMI for the presence or absence of hepatic steatosis.

All ROC curves were statistically significant with P<0.001. The best area under de ROC curve was that of waist circumference (0.935±SE 0.027) which was better than those of WHR (difference 0.08, 95% confidence interval 0.01–0.16), VAI (difference 0.18, 95% confidence interval 0.10–0.26 and MOAD (difference 0.17, 95% confidence interval 0.08–0.26), but was not different than that of BMI (difference 0.02, 95% confidence interval −0.01 – to 0.05, P = 0.155). Similarly, the area under the ROC curve of BMI was better compared with those of VAI (difference 0.16, 95% confidence interval 0.08–0.24, P<0.001) and MOAD (difference 0.15, 95% confidence interval 0.04–0.26, P = 0.007) but was not different than that of WHR (difference 0.06, 95% confidence interval 0.03 – to 0.15, P = 0.176).