A new randomized crossover trial published in the American Journal of Clinical Nutrition challenges the conventional assumption that protein grams alone determine muscle-building outcomes. Researchers found that lean pork stimulates muscle protein synthesis approximately 47% more effectively than high-fat pork when both sources contain identical protein content and are consumed after resistance exercise.
The mechanism centers on digestion speed and amino acid bioavailability. High-fat protein sources delay the appearance of leucine—a critical branched-chain amino acid that activates the mTORC1 signaling pathway essential for muscle growth. The advantage of lean protein proves strongest within the first 3–5 hours post-exercise, when rapid amino acid delivery has the greatest impact on muscle adaptation.
However, the researchers note that at higher daily protein intakes distributed across multiple meals, the fat content of individual meals becomes less influential on long-term muscle development. This nuanced finding suggests that meal timing and composition warrant consideration in sports nutrition planning.
Read the full article on GMJ Newsroom.
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