Visceral adipose tissue: relations between single-slice areas and total volume

Abstract

Background: Visceral adipose tissue (VAT), which is linked with the metabolic consequences of obesity, is usually characterized by measuring VAT area at the L4-L5 vertebral interspace. However, the location of the slice with the strongest relation to VAT volume is not established.

Objective: We sought to investigate the relations between cross-sectional VAT areas at different anatomic locations and VAT volume in a large, diverse sample of healthy subjects.

Design: VAT volume was derived from slice areas taken at 5-cm intervals from magnetic resonance images in 121 healthy men [x +/- SD age: 41.9 +/- 15.8 y; body mass index (BMI; in kg/m(2)): 26.0 +/- 3.2; VAT: 2.7 +/- 1.8 L] and 198 healthy women (age: 48.1 +/- 18.7 y; BMI: 27.0 +/- 5.4; VAT: 1.7 +/- 1.2 L). Regression models were developed to identify the best single slice for estimating VAT volume.

Results: The VAT area 10 cm above L4-L5 (A(+10)) in men (R(2) = 0.932, P < 0.001) and 5 cm above L4-L5 (A(+5)) in women (R(2) = 0.945, P < 0.001) had the highest correlation with abdominal VAT. R(2) increased by only 3.8% in men and 0.5% in women with adjustment for age, race, scanning position, BMI, and waist circumference. Studies using A(+10) in men and A(+5) in women will require 14% and 9% fewer subjects, respectively, than those using slices at L4-L5 and will have equivalent power.

Conclusion: Measurement of slice areas at A(+10) in men and A(+5) in women provides greater power for the detection of VAT volume differences than does measurement at L4-L5.

FIGURE 1

Relation between abdominal visceral adipose tissue (VAT) volumes and VAT area 10 cm above L4–L5 in men (A) and 5 cm above L4–L5 in women (B). Both the coefficient for VAT area and the intercept of the equation are significantly different from 0 (P < 0.001). Note that the scales of both axes differ between the 2 panels of the figure.

FIGURE 2

Relations between correlation coefficients (○) and anatomic location and between visceral adipose tissue (VAT) slice areas (■) and anatomic location. The data were fitted with 4th-order polynomial equations in men (A), and women (B). L4–L5 is taken as the zero point, and slices are identified as being taken from below (−) or above (+) this location.