What is the best time of day to eat protein for your muscles?

Distribution throughout the day is what matters most. Portions of 20-40 g of high-quality protein, roughly every 3 to 4 hours, give your muscles the best stimulus. One large portion at the end of the day, or very small snacks spread throughout, works less well. This applies on both training days and rest days.

Just how large the difference is was shown in a controlled experiment: 80 g of whey protein distributed in portions of 20 g every 3 hours produced 31 to 48% more muscle protein synthesis than the same amount taken in small doses of 10 g every 1.5 hours, or in large portions of 40 g every 6 hours. That is a considerable margin. The lesson: not too small, not too large, not too far apart.

Protein after a workout also has an effect, but less so than you might think. Eating high-quality protein immediately up to around 2 hours after resistance training increases muscle protein synthesis. Whether that provides a genuine additional benefit depends on what you ate before the workout: a substantial meal shortly beforehand reduces the advantage of the post-training portion. Overall daily distribution counts for more than the precise timing around your workout.

An extra opportunity lies in the night. Around 30 to 40 g of casein protein taken just before going to sleep increases muscle protein synthesis during the night, without disrupting fat burning. Casein digests more slowly than whey and is therefore well suited to this nocturnal portion. The evidence for this is still limited in scale, but the direction is positive.