I never put the two-and-two together and realized that this loss is "normal" with age, and accelerates especially past the 80s. Despite what you eat, the body is working against maintaining muscle.
I'm concerned only because I see it in my dad, who eats great, and yet he is getting weaker and weaker, which make taking care of him harder and harder. Some of the studies say even one session a week of resistance (weight) training can increase protein synthesis and muscle retention by 50%. Why don't docs and articles even discuss this? I would gleefully go thru a workout session once a week to ward off having to lift him out of bed!