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

Little 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.Older 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.After 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).WL + 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.