Evaluating CMR

Dual-Energy X-Ray Absorptiometry (DEXA)

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DEXA can also be used to assess central adiposity. DEXA measures of total abdominal fat correspond very well to measures of total abdominal fat by CT (11, 12). However, DEXA is unable to distinguish subcutaneous fat from intra-abdominal fat as it can only assess body composition two-dimensionally. As such, the association between DEXA measures of abdominal fat and CT or MRI measures of intra-abdominal fat tends to be much weaker than for total abdominal fat (11-14). Some have argued that the association between intra-abdominal fat and DEXA-measured abdominal fat is no better than that observed with simple tools such as waist circumference (11, 12, 15) and sagittal diameter (11, 12, 14). Further, DEXA can give rise to a phenomenon known as “beam hardening,” which may cause the true fat content of individuals with a large sagittal diameter (i.e., some obese individuals) to be underestimated (5, 9). Adiposity is more likely to be underestimated in the trunk than in the extremities, which have a smaller sagittal diameter.

DEXA is a useful tool for assessing total and abdominal obesity. However, DEXA is unable to break down abdominal fat into its subcutaneous and intra-abdominal fat components. In terms of accuracy, DEXA estimates of intra-abdominal fat are similar to those obtained by anthropometric measures such as waist circumference.

Reference

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5. Genton L, Hans D, Kyle UG, et al. Dual-energy X-ray absorptiometry and body composition: differences between devices and comparison with reference methods. Nutrition 2002; 18: 66-70.

9. Salamone LM, Fuerst T, Visser M, et al. Measurement of fat mass using DEXA: a validation study in elderly adults. J Appl Physiol 2000; 89: 345-52.

11. Snijder MB, Visser M, Dekker JM, et al. The prediction of visceral fat by dual-energy X-ray absorptiometry in the elderly: a comparison with computed tomography and anthropometry. Int J Obes Relat Metab Disord 2002; 26: 984-93.

12. Clasey JL, Bouchard C, Teates CD, et al. The use of anthropometric and dual-energy X-ray absorptiometry (DXA) measures to estimate total abdominal and abdominal visceral fat in men and women. Obes Res 1999; 7: 256-64.

13. Park YW, Heymsfield SB and Gallagher D. Are dual-energy X-ray absorptiometry regional estimates associated with visceral adipose tissue mass? Int J Obes Relat Metab Disord 2002; 26: 978-83.

14. Kamel EG, McNeill G, Han TS, et al. Measurement of abdominal fat by magnetic resonance imaging, dual-energy X-ray absorptiometry and anthropometry in non-obese men and women. Int J Obes Relat Metab Disord 1999; 23: 686-92.

15. dos Santos RE, Aldrighi JM, Lanz JR, et al. Relationship of body fat distribution by waist circumference, dual-energy X-ray absorptiometry and ultrasonography to insulin resistance by homeostasis model assessment and lipid profile in obese and non-obese postmenopausal women. Gynecol Endocrinol 2005; 21: 295-301.

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