One-Year Lifestyle Intervention, Muscle Lipids, and Cardiometabolic Risk

PURPOSE: Low-attenuation muscle (LAM) area at mid-thigh, a computed tomography (CT)-derived index of intramuscular lipids, is associated with insulin resistance, obesity, and type 2 diabetes. The present study aimed at testing the hypothesis that changes in LAM area in trunk muscles from a single abdominal scan could provide relevant information to evaluate the effects of a lifestyle intervention without the use of a mid-thigh CT scan. METHODS: Cardiometabolic risk variables, including waist circumference, lipoprotein-lipid profile, glucose tolerance, and cardiorespiratory fitness, were assessed in a sample of 102 dyslipidemic viscerally obese men at baseline and after a 1-yr lifestyle intervention. Abdominal (L4-L5) and mid-thigh CT scans were performed and abdominal muscles classified as psoas and core muscles. Scans were segmented to calculate muscle areas, LAM areas, and mean attenuation values. RESULTS: All muscle groups showed a decrease in LAM areas (P < 0.0001) in response to the lifestyle intervention. Changes in LAM areas were significantly associated with changes in triglycerides, high-density lipoprotein (HDL) cholesterol, cholesterol/HDL cholesterol ratio and log triglycerides/HDL cholesterol ratio (mid-thigh, 0.20 ≤ |r| ≤ 0.29; psoas, 0.28 ≤ |r| ≤ 0.38; core, 0.29 ≤ |r| ≤ 0.34, P < 0.05). Changes in core LAM area were significantly associated with changes in 2-h glucose levels, glucose area measured during the oral glucose tolerance test and homeostasis model assessment of insulin resistance (0.21 ≤ r ≤ 0.34, P < 0.05). Stepwise regression analyses showed that changes in LAM psoas area were associated with changes in HDL cholesterol and the cholesterol/HDL cholesterol ratio independently from changes in visceral adiposity. CONCLUSIONS: Changes in trunk LAM areas are useful indices of changes in mid-thigh LAM area observed with a 1-yr lifestyle intervention. Thus, an additional mid-thigh scan is not necessary to evaluate muscle lipid content by CT when an abdominal CT scan is available.