Anabolic resistance can manifest at multiple physiological levels, including digestion, absorption, splenic sequestration of amino acids, insulin's role in perfusion, muscle uptake, and intracellular signaling pathways like the mTOR pathway.

“but that doesn't mean that aging inherently doesn't also account for some of this and there are lots of hypotheses that he put forward is there a decrease in amino acid uptake a decrease in gut absorption a decrease in the circul of amino acids um something called splenic sequestration going up so basically losing amino acids to the splank niic system in the in the GI tract reduction of perfusion of course that's true elsewhere in the body so maybe it's true here um and lower muscle uptake finally lower mtor signaling it certainly is listed as one of the Hallmarks of Aging that nutrient sensing goes down”