Effects of weight loss or exercise on muscle quality in obese older women

Abstract

A key component in lower extremity physical function in older obese women is leg muscle quality (MQ), defined as: a) strength per muscle quantity or b) the degree of adipose intermuscular adipose tissue (IMAT) within the muscle. This pilot study assessed the relative impact of a weight loss diet (WL‐D) or exercise (EX) on MQ. Sedentary obese (BMI ≥ 30–35 kg/m2) women (N = 30) were randomized to a WL‐D or EX intervention for 16 weeks. Thigh subcutaneous adipose tissue (SAT), IMAT, and muscle (MUSC) was quantified by MRI. Strength was assessed via maximal isometric (IM) and isokinetic (at 60 deg/sec, IK60) contractions using an isokinetic dynamometer and calculated as Nm/(m3). WL‐D (n=8, 65.6±8.0 y) lost 2.4±3.9 kg of body weight (p=0.12) and EX (n=11, 63.7±4.5 y) lost did not change (0.06±1.8 kg; p=0.91). Changes in upper leg composition or MQ measures did not significantly differ between groups; however; a) SAT decreased 3.5% in WL‐D (p=0.11) and 3% in EX (p=0.01), b) IMAT increased 7% in WL‐D (p=0.04) but only 2.7% in EX (p=0.27), c) MUSC increased 3.6% in WL‐D (p=0.34) and 4.5% in EX (p=0.06), d) EX increased MQ‐IM 7.3% (p=0.17) and MQ‐IK60 1.6% (p=0.80) whereas WL‐D increased MQ‐IM 0.89% (p=0.79) and decreased MQ‐IK60 −8.2% (p=0.12). Weight loss and exercise may have differential effects on thigh composition and MQ in older obese women. Supported by NIH‐HL090455