We thank Drs. Kelly, Gandham, and Nanan for their suggestion to investigate the accuracy of the tri-ponderal mass index (TMI; weight/height3)1 versus BMI in estimating visceral adipose tissue (VAT) percentage in adolescents. We agree with the authors that estimating VAT may better identify adolescents at-risk for insulin resistance and dyslipidemia, leading to better risk stratification.2 While the National Health and Nutrition Examination Survey (NHANES) dataset includes VAT data as measured by Hologic’s (Marlborough, MA) dual-energy x-ray absorptiometry (DXA) system in adults, it does not currently include VAT data for adolescents. To date, the Food and Drug Administration (FDA) has approved Hologic’s DXA software to report VAT in only adults. There have been several studies that have compared manually-derived DXA estimates of VAT to computed tomography (CT) measurements of VAT.3–5 These estimations rely on assumptions involving the distribution of fat in adults, which may not be valid before puberty. As evidence, the correlations between manually-derived DXA estimates and CT measurements are indeed substantially lower in adolescents than in adult populations.2,6 Nonetheless, there are CT and MRI studies that can be pooled to provide a preliminary indication of how well TMI and other indices such as BMI predict VAT in adolescents. Moreover, as technology evolves, we anticipate that DXA-derived estimates of VAT in adolescents will improve in accuracy and eventually be approved by the FDA. In summary, a full-scale analysis similar to the one we recently performed relating TMI to total body fat in adolescents1 is not yet feasible for VAT, but we look forward to it being a possibility in the near future.
Footnotes
Conflicts of Interest Disclosure: CMP has nothing to disclose. SBH reports serving on the medical advisory boards of Medifast and Rice Lake Weighing System, in capacities unrelated to the scope of the reported research. DMT reports being involved in developing SmartLoss®, a trademarked smartphone weight loss intervention that is registered under Louisiana State University System. DMT had no financial affiliations with the companies who conducted the work to develop the SmartLoss® Virtual Weight Management Suite. Any licensing of SmartLoss® could financially benefit Montclair State University and DMT.
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