For decades, the "anabolic window" - a 30-minute post-workout period for protein consumption - was presented as critical for muscle growth. More recent research has refined this picture considerably. This guide covers what the evidence actually shows about protein timing, daily targets, and how to structure intake for optimal muscle protein synthesis.
Daily Protein Targets
Total daily protein intake is the primary determinant of muscle protein synthesis over time. The current evidence supports: 1.6g/kg bodyweight/day as the minimum for muscle maintenance and modest growth in trained individuals. 1.8 - 2.2g/kg/day for active muscle-building phases. 2.2 - 2.4g/kg/day during caloric deficit (to preserve lean mass). Beyond approximately 2.4g/kg, additional protein provides minimal additional MPS benefit in most individuals, though it causes no harm.
The Anabolic Window: What Research Actually Shows
A landmark 2013 meta-analysis by Schoenfeld and Krieger analysed 23 studies and found that total daily protein intake explained virtually all variance in muscle gains - not protein timing. The "window" is real but wider than thought: muscle sensitivity to protein-driven MPS is elevated for 4 - 6 hours post-training, not 30 minutes. The practical implication: eat a protein-rich meal within a few hours of training; obsessing over exact timing is unproductive.
Per-Meal Leucine Threshold
The key per-meal concept is the leucine threshold - the amount of leucine needed to maximally stimulate mTOR and initiate MPS. Research by Moore et al. suggests 3 - 4g leucine per meal triggers near-maximal MPS stimulation. For whey protein isolate (11% leucine), this requires approximately 25 - 35g protein per meal. Larger servings (40g) don't dramatically increase the MPS response but extend its duration.
Pre-Sleep Protein
Casein protein (slow-digesting) taken before bed has consistent evidence for supporting overnight muscle protein synthesis. Snijders et al. showed 40g casein before sleep significantly increased overnight MPS rates versus placebo in resistance-trained men. Cottage cheese (high casein content) is an effective food alternative.
Practical Structure
4 - 5 meals containing 35 - 45g high-quality protein (leucine >3g) spread across the day, with one serving post-training and one before sleep. Whey protein isolate is the optimal post-training source; casein or a mixed food source is optimal pre-sleep.