Muscle

Muscle is contractile protein tissue that stores glycogen and generates heat and movement. Adequate thyroid function and protein with carbohydrate build and maintain it; cortisol breaks it down under stress.

A self-reinforcing catabolic loop

Ray Peat described a feedback mechanism by which muscle breakdown itself drives further muscle breakdown: the tryptophan and cysteine released when muscle is catabolized suppress the thyroid and raise serotonin, which in turn raises cortisol:

The formation of serotonin is increased by the excess tryptophan in muscle, and serotonin stimulates the formation of more cortisol, while the tryptophan itself, along with the excess muscle-derived cysteine, suppresses the thyroid function.

— Ray Peat

Because this loop is triggered by the amino acid mix, not just the presence of stress itself, Peat's practical fix was balancing muscle-meat protein with gelatin (see Taurine and Carnitine for the specific quote and dosing note), which supplies the glycine that offsets tryptophan and cysteine's effects.

Practice

Train and eat adequately, thyroid and food together, not exercise alone, build and maintain muscle. Balance muscle-meat protein with gelatin rather than eating unbalanced lean meat as the sole protein source: for a half-pound of steak, roughly 20 grams of gelatin at the same meal is a reasonable starting ratio, with a higher gelatin-to-meat ratio often preferable. See Protein, Gelatin, Thyroid, Cortisol, Glycogen.

See also

• Protein
• Gelatin
• Exercise
• Testosterone
• Cortisol