For those of us with higher fat percentages, how real of a danger is this?

I was reading another post where the op mentioned their friends were concerned about them losing muscle mass, and I've seen it mentioned rather frequently that this is something to be aware of.

My starting weight was over 400lbs, this medication is a hugely important tool for me in both my weight and mental health journeys. I'm breaking down a lot of the shit I've been through and gaining an understanding of why food has been such a huge part of my coping skills.

All that to say, I have a fair amount of muscle due to my body's natural build, but also to help carry the weight I've gained. I'm wondering at what point does the muscle mass come into play? Like, if I don't eat at all for several weeks (this is not the plan, promise) I'll burn fat for the energy I need, yeah? But does the body ever skip over the fat to burn through muscle mass when there's fat to burn?

I'm pretty sure I understand the actual science, I'm looking for a clearer understanding.