Newbie-like results

i remember a thread a while back about gaining lean mass while simultaneously losing fat. some of the ideas involved very specific timing of the intake of certain macronutrient combinations throughout the day.

now, instead of focusing just on diet, what about prioritizing a smaller muscle group while consuming less than a maintenance amount of food? since the smaller muscle group (arms, shoulders, or calves) would need less spare protein to grow, it seems at least somewhat possible for that group to grow while still losing fat. (or at least less impossible than legs)

i'm sure there is plenty of anecdotal evidence for this phenomena occuring, but that type of evidence really doesn't mean anything. does anyone know of any physiological reasons why this is completely impossible or maybe worth thinking about?

i know this is probably total minutia, but i’m sure i’m not the only one who’s ever thought about it.