Diet- and Exercise-Induced Weigh Loss Lowers Intermuscular Fat and Low-Density Muscle in Overweight Individuals

Abstract

It is well known that diet and exercise can improve metabolic fitness and reduce the risk factors of the metabolic syndrome, including regional adiposity. Intermuscular adiposity has been strongly associated with insulin sensitivity. PURPOSE: We wanted to determine whether intermuscular lipids and low-density thigh muscle attenuation (fat lipid accumulation between and within the muscle fibers), as measured by computed tomography (CT), decreases with diet- and exercise-induced weight loss and whether these changes were associated with changes in insulin sensitivity as measured by homeostatic assessment (HOMA). METHODS: Overweight adults (age=40 ± 2, n=25), with at least two characteristics of the metabolic syndrome, participated in a 4–7 m weight loss program that consisted of both energy restriction (reduced by ∼500 kcal/d) and exercise (5 d/wk; 45 min/d at 75% HRmax) to induce weight reduction by 10%. Thigh muscle CT was used to assess intermuscular fat (IMFat) and muscle attenuation in a 10 mm mid-thigh cross-sectional scan at baseline (bl) and post-weight loss (pwl). RESULTS: Intervention decreased body weight by 9.3 ± 0.3%, total adipose tissue area by 12.7% (bl: 172.17 ± 13.05 vs. pwl: 150.29 ± 11.34; p< 0.001) and high-density muscle area by 2.7% (bl: 119.81 ±6.20 vs. pwl: 116.65 ± 5.40; p=0.029). At baseline, there was no significant correlation between both IMF at (r=−0.119, p=0.572) and low-density muscle area (LDM, cm2) (r=0.019, p=0.927) with HOMA. Weight loss produced a 16% decrease in IMFat (bl: 22.48 ± 1.25 vs. pwl: 18.85 ± 1.11; p<0.001) and a 6.9% decrease in LDM (bl: 21.77 ± 1.23 vs. pwl: 20.26 ± 1.18; p=0.008), but there was no significant correlation between the changes in HOMA and the changes in IMFat (r=−0.282,p=0.173) or LDM (r=0.137, p=0.515). CONCLUSION: Diet- and exercise-induced weight loss (∼10%) resulted in decreased IMFat and LDM area which were not correlated with improvements in insulin sensitivity.