️More protein = more muscle retention?️This relatively new systematic review with meta-regression by my friend @mrfitness__ & colleagues, analyzed 29 studies to examine the relationship between dietary protein intake and fat-free mass retention in resistance-trained individuals undergoing energy restriction.
The findings suggest a linear relationship between protein intake and FFM retention, with higher intakes (up to 3.2 g/kgBM or 4.2 g/kgFFM/day) linked to better outcomes, though the effect size was small, and with lower degree of certainty given limited data.
Nonetheless, the study found that leaner individuals, men, and those in longer dieting phases (>4 weeks) benefited most from higher protein intake, while individuals with higher body fat percentages showed weaker responses.
Importantly, training itself was identified as a very critical factor in preserving muscle mass, with the size of the calorie deficit also playing a significant role.
Quite in fact, the paper suggests that excessively high protein intakes can also result in drastic reductions of carbohydrates and fats, which may negatively impact training performance and hormone balance.
Overall, based on these findings, a protein intake of at least 1.9 g/kgBM or 2.5 g/kgFFM/day is necessary to prevent muscle loss, while higher intakes may offer additional, though modest, benefits—particularly for those who are very lean or in extended deficits.
Reference: Effect of Dietary Protein on Fat-Free Mass in Energy Restricted, Resistance-Trained Individuals: An Updated Systematic Review With Meta-Regression
