Submitted to: Obesity
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/28/2006
Publication Date: 6/1/2007
Citation: Ellis, K.J., Grund, B., Visnegarwala, F., Thackeray, L., Miller, C.G., Chesson, C.E., El-Sadr, W., Carr, A. 2007. Visceral and subcutaneous adiposity measurements in adults: Influence of measurement site. Obesity. 15:1441-1447. Interpretive Summary: An accumulation of excess abdominal fat increases the risk for a number of serious chronic diseases. In the abdomen, fat is stored both just below the skin and deeper within the body, around vital organs. Only advanced imaging techniques, such as computed tomography (CT), can be used to assess the intra-abdominal or visceral fat stores. The question is where is the best location in the abdomen to make this assessment? Or, does it need to be examined at multiple sites? We looked at nine different locations in the lower abdomen of 24 adults, and compared differences among the locations for each subject, and between subjects. Moving from the region just below the ribs to the pelvic region lower on the abdomen, the amount of fat under the skin decreases slowly, while the amount of fat deep within the body increases substantially. Our results show the limitation of using a single-slice to measure abdominal fat distribution, and the error that could be introduced if a subject is not repositioned at the exact same location for follow-up exams. Our findings indicate that multi-locations along the abdomen need to be examined in order to provide the more complete assessment of abdominal fat distribution.
Technical Abstract: Excess abdominal adiposity is a known risk factor for cardiovascular diseases. Computed tomography can be used to examine the visceral (VAT) and subcutaneous (SAT) components of abdominal adiposity, but it is unresolved whether single-slice or multi-slice protocols are needed. Nine computed tomography scans were obtained in the lumbar spine region of 24 adults. The nine slices were obtained at three intervertebral positions (L2-L3, L3-L4, and L4-L5) and at 7 mm above and below these locations. Intra-site and inter-site differences in SAT, VAT, total adipose tissue, and the VAT/SAT ratio were examined using ANOVA and confidence intervals for pairwise differences between means. Intervertebral SAT values increased from 103.1 +/- 50.9 (standard deviation) cm(2) at L2-L3 to 153.3 +/- 68.8 cm(2) at L4-L5, whereas the corresponding VAT values decreased from 164.3 +/- 125.4 to 126.0 +/- 82.7 cm(2). The VAT/SAT ratio was not constant, decreasing from 1.8 +/- 1.4 to 0.9 +/- 0.7. Repeated-measures ANOVA indicated significant inter- and intra-site differences (p </= 0.02) for SAT, VAT, and the VAT/SAT ratio at L3-L4 and L4-L5 (p < 0.001). These differences show the limitation of using a single-slice assessment of abdominal fat distribution, both for a subject and between subjects. Furthermore, the sizeable differences in the intra-site scans indicate that precise repositioning is needed for longitudinal studies. In summary, our findings suggest that a multi-site imaging protocol may provide a more complete assessment of abdominal fat stores and distribution than use of a single site.