While some loss of lean body mass is usually inevitable, I wouldn’t be so quick to write off muscle in exchange for weight loss.
Muscle tissue uses a fair number of calories even when not being used in relation to other cells, it’s something like six times the amount of fat tissue. It’s not hundreds of calories extra a day or anything, but it really adds up over time.
Losing the muscle you have is just losing extra metabolism and means you need to deficit more. So it’s only going to be easier in the long run to shift some more calories into protein to maintain or at least minimize losses.