Is There a Minimum Protein Intake Associated With Resistance Training to Optimize Skeletal Muscle Mass Gains in Untrained Older Women?

Ribeiro, AS, Alencar da Silva, J, Kassiano, W, Stavinski, N, Martino, D, Antunes, M, Cyrino, LT, Sugihara Júnior, P, Fernandes, RR, Santos, AP, Rodrigues, RJ, Aguiar, AF, and Cyrino, ES. Is there a minimum protein intake associated with resistance training to optimize skeletal muscle mass gains in untrained older women? J Strength Cond Res 39(7): 730-735, 2025-This study explored the relationship between habitual total daily protein intake and its effects on skeletal muscle mass (SMM) and body fat mass in a group of healthy, physically independent older women participating in resistance training (RT). The data were retrospectively analyzed from 97 previously untrained older women (age: 68.6 ± 6.3 years; mass: 65.7 ± 11.8 kg; height: 155.2 ± 6.0 cm; body mass index: 27.2 ± 4.3 kg·m -2 ). Subjects were engaged in a whole-body RT program for 24 weeks, which consisted of 8 exercises performed in 3 sets of 8-15 repetitions 3 times a week. The SMM and body fat mass were determined by dual-energy X-ray absorptiometry, while food consumption was evaluated using the 24-hour dietary recall method. A positive correlation was found between daily protein intake (g·kg -1 ·d -1 ) and changes in SMM ( r = 0.23, 95% confidence interval [CI] = 0.03-0.41; p = 0.022). Furthermore, segmented regression analyses revealed a significant positive relationship between daily protein intake and SMM changes ( β = 1.34; p = 0.007), with an estimated breakpoint approximately 1.1 g·kg -1 ·d -1 (95% CI: 0.9-1.3). However, according to linear regression and biphasic linear regression models, there was no significant relationship between body fat mass changes and daily protein intake ( p > 0.05). Our results suggest that a habitual protein intake of approximately 1.1 g·kg -1 ·d -1 associated with RT may be necessary to optimize gains in SMM in untrained older women.