Effect of exercise modality and weight loss on changes in muscle and bone quality in older adults with obesity

Abstract

BackgroundLittle is known about the effect of exercise modality during a dietary weight loss program on muscle size and quality, as measured by computed tomography (CT). Even less is known about how CT-derived changes in muscle track with changes in volumetric bone mineral density (vBMD) and bone strength. MethodsOlder adults (66 ± 5 years, 64 % women) were randomized to 18-months of diet-induced weight loss (WL), WL with aerobic training (WL + AT), or WL with resistance training (WL + RT). CT-derived muscle area, radio-attenuation and intermuscular fat percentage at the trunk and mid-thigh were determined at baseline (n = 55) and 18-month follow-up (n = 22–34), and changes were adjusted for sex, baseline value, and weight lost. Lumbar spine and hip vBMD and finite element-derived bone strength were also measured. ResultsAfter adjustment for the weight lost, muscle area losses at the trunk were −7.82 cm2 [−12.30, −3.35] for WL, −7.72 cm2 [−11.36, −4.07] for WL + AT, and −5.14 cm2 [−8.65, −1.63] for WL + RT (p < 0.001 for group differences). At the mid-thigh, decreases were −6.20 cm2 [−10.39, −2.02] for WL, −7.84 cm2 [−11.19, −4.48] for WL + AT, and −0.60 cm2 [−4.14, 2.94] for WL + RT; this difference between WL + AT and WL + RT was significant in post-hoc testing (p = 0.01). Change in trunk muscle radio-attenuation was positively associated with change in lumbar bone strength (r = 0.41, p = 0.04). ConclusionsWL + RT better preserved muscle area and improved muscle quality more consistently than WL + AT or WL alone. More research is needed to characterize the associations between muscle and bone quality in older adults undertaking weight loss interventions.