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Abdominal Adiposity Assessed by Dual Energy X-Ray Absorptiometry Provides a Sex-Independent Predictor of Insulin Sensitivity in Older Adults

Department of Internal Medicine, Division of Geriatrics, University of Michigan Health System, and the GRECC VA Ann Arbor Healthcare System.

Address correspondence to Cathy C. Lee, MD, VA Ann Arbor Healthcare System, 2215 Fuller Road, GRECC 11-G, Ann Arbor, MI 48105. E-mail: clchopra{at}umich.edu

Background. An increase in total adiposity and in particular an abdominal distribution of adiposity may contribute to the decline in metabolic insulin sensitivity observed in older men and women. The objective of this cross-sectional study was to determine which measure of abdominal adiposity would provide the best sex-independent predictor of metabolic insulin sensitivity in older men and women.

Methods. Insulin sensitivity and abdominal adiposity were measured in healthy, nondiabetic older (64 ± 6 years; mean ± standard deviation) men (n = 23) and women (n = 31). Metabolic Insulin Sensitivity Index (S_I) was determined from a frequently sampled insulin-assisted intravenous glucose tolerance test. Body fat mass and abdominal fat mass were determined from dual energy X-ray absorptiometry (DXA) scans. Anthropometric measures included waist and hip circumferences, height, and body weight.

Results. Although waist circumference, waist index (waist circumference divided by height), and waist–hip ratio (WHR) were all lower in women than in men, there was no sex difference in DXA L1–L4 fat mass. In univariate analyses, S_I was significantly inversely related with body weight, body mass index, waist circumference, waist index, percentage of total body and abdominal fat, and DXA L1–L4 fat mass but not with WHR. The DXA L1–L4 fat mass was identified as the best independent predictor of S_I, accounting for 41.2% of the variance (p <.0001) in a stepwise multiple regression model that controlled for sex.

Conclusions. WHR is not associated with S_I in either men or women. Abdominal adiposity measured by DXA L1–L4 fat mass provides a sex-independent predictor of S_I in older men and women.