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Reduction in Midthigh Low-Density Muscle with Aerobic Exercise Training and Weight Loss Impacts Glucose Tolerance in Older Men

Division of Gerontology, University of Maryland School of Medicine and Baltimore Geriatric Research, Education and Clinical Center (S.J.P., L.J.J., L.I.K., J.M.H., A.S.R.), Veterans Administration Maryland Health Care System, Baltimore, Maryland; and Department of Kinesiology (S.J.P., J.B., J.M.H.), University of Maryland, College Park, Maryland

Address all correspondence and requests for reprints to: Steven J. Prior, Ph.D., Baltimore Veterans Administration Medical Center, Geriatrics (18), Room 4B-205, 10 North Greene Street, Baltimore, Maryland 21201. E-mail: sprior{at}grecc.umaryland.edu.

Context: Intramuscular lipid content increases with aging and obesity and is directly related to impaired glucose tolerance and insulin resistance.

Objective: Our purpose was to determine the effects of aerobic exercise training (AEX) with and without weight loss (WL) on midthigh low-density muscle (LDM; a measure of im lipid) and whether changes in LDM impact glucose tolerance in sedentary older men.

Design: Forty-six men (60.4 ± 1.1 yr) completed 6 months of AEX (n = 34) or AEX + WL (n = 12) and had oral glucose tolerance tests (OGTTs) and computed tomography measures of LDM and regional abdominal and thigh fat depot areas.

Results: At baseline, LDM area directly correlated with fasting plasma glucose (FPG), 120-min glucose (G₁₂₀), and glucose area under the curve (G_AUC) during an OGTT (r = 0.44, r = 0.51, and r = 0.54, respectively, P < 0.01). After the interventions, the AEX + WL group had greater decreases in LDM (–13.5 vs. +1.3%, respectively), FPG (–8.3 vs. +2.1%, respectively), G₁₂₀ (–22.5 vs. –3.6%, respectively), and G_AUC (–17.3 vs. – 3.1%, respectively) than the AEX group. In the entire sample, the decreases in LDM correlated with reductions in FPG, G₁₂₀, and G_AUC during an OGTT (r = 0.31, r = 0.34, and r = 0.41, P < 0.05). Changes in other regional fat depots did not independently correlate with glucose tolerance or insulin responses.

Conclusion: AEX + WL is more efficacious than AEX for reducing LDM and glucose tolerance. The improvement in glucose tolerance may be partially mediated by decreases in LDM in older men.