Effects of protein supplementation combined with resistance exercise on body composition and physical function in older adults: a systematic review and meta-analysis

Abstract Background: Overweight and obese older people face a high risk of muscle loss and impaired physical function, which may contribute to sarcopenic obesity. Resistance exercise training (RET) has a beneficial effect on muscle protein synthesis and can be augmented by protein supplementation (PS). However, whether body weight affects the augmentation of muscular and functional performance in response to PS in older people undergoing RET remains unclear. Objective: This study was conducted to identify the effects of PS on the body composition and physical function of older people undergoing RET. Design: We performed a comprehensive search of online databases to identify randomized controlled trials (RCTs) reporting the efficacy of PS for lean mass gain, strength gain, and physical mobility improvements in older people undergoing RET. Results: We included 17 RCTs; the overall mean ± SD age and body mass index (BMI; in kg/m2) in these RCTs were 73.4 ± 8.1 y and 29.7 ± 5.5, respectively. The participants had substantially greater lean mass and leg strength gains when PS and RET were used than with RET alone, with the standard mean differences (SMDs) being 0.58 (95% CI: 0.32, 0.84) and 0.69 (95% CI: 0.39, 0.98), respectively. The subgroup of studies with a mean BMI ≥30 exhibited substantially greater lean mass (SMD: 0.53; 95% CI: 0.19, 0.87) and leg strength (SMD: 0.88; 95% CI: 0.42, 1.34) gains in response to PS. The subgroup of studies with a mean BMI