Effects of daily protein intake frequency during 8 weeks of resistance training on lean mass and strength adaptations: a randomized non-controlled clinical trial.

Background: The optimal protein intake distribution per meal for maximizing muscle mass and strength gains remains debated in current literature. This study investigated the outcomes of different protein distributions on muscle strength and body composition in healthy, young, resistance-trained men.

Methods: Thirty-two young resistance-trained men were randomly allocated into two groups based on the number of protein-supplemented meals (>0.24 g/kg/meal): three high-protein meals (PRO3x) or five high-protein meals (PRO5x). Both groups had a similar daily protein intake but different meal distribution patterns. At baseline and after eight weeks of resistance training, subjects were evaluated for the cross-sectional area (CSA) of lower limb muscles (ultrasound), body composition (DXA), body weight, and muscle strength (knee extension 1RM).

Results: Eighteen participants completed the study protocol and significant improvements over time (P<0.05) were observed in both groups, with increases in lean mass (PRO3x: 1.15±1.54 kg; PRO5x: 0.63±1.32 kg), vastus lateralis muscle CSA (PRO3x: 3.41±3.79 cm²; PRO5x: 2.53±3.31 cm²), and knee extension 1RM (PRO3x: 19.08±7.56 kg; PRO5x: 16.01±5.17 kg), with no significant differences between groups.

Conclusions: Therefore, consuming protein three or five times a day in energetically balanced, optimal amounts per meal is equally effective in supporting resistance training-induced gains in muscle mass and strength.