That fear is old school bro science nonsense. Our bodies MUST go catabolic. Your body doesn’t just start eating muscle because it has nothing better to do, it will always metabolize fat stores first just like it will always metabolize alcohol before carbs, carbs before fats, and fats before muscle. Breaking down lean mass for fuel is an absolute last resort.
Your body also catabolizes damaged muscle after you work out so it can rebuild bigger, nobody views it that way though. Also no different than liquifying a hunk of steak in your stomach to feed your muscles. Catabolism is part of our metabolism. It’s not something to fear.