Most people know that once the body has run out of everything else it will start to break down muscle protein into amino acids to keep the brain alive; a process of self-cannibalism known as catabolism.
But for survival some muscle tissue is more important than others - the auricular muscles that enable some people to wiggle their ears are less important than the quadriceps, which are in turn less important than the heart.
Does the body prioritise which muscles it starts to chow down on when you are starving to death or does all muscle degrade at the same rate? What would you first notice if you had exhausted all other fuel sources?
Skeletal muscle before heart muscle and pretty sure smooth muscle.
Pretty sure smooth muscle before heart muscle too.
Between skeletal muscle I am not sure. One the one hand one might guess that muscle most used will be most likely preserved but then again using it might cause more breakdown without enough energy or raw material to build it back up again, so I don’t know.
(Actually btw there is some muscle mass loss with most caloric restriction sufficient to cause weight loss, not only in starvation circumstances. Catabolism is a constant, along with anabolism, in some balance every day, not only in extremis. Preventing that muscle loss with weight loss requires gradual loss coupled with adequate quality protein and resistance exercise.)