I hear you with about eating. After the debulking surgery on my spine in 2021 (10+ hours under general anesthesia), my digestive system refused to restart -- something called an "Ileus", except that mine lasted a couple of weeks, which had the doctors and nurses worried. I had a suction tube down my nose into my stomach and was on I/V feeding for a while. Even after that, I struggled to make it to 500 cal/day, just like you, and lost 40 lb in a few weeks. I didn't really start recovering my appetite until I was cleared to transfer by myself from the hospital bed to the wheelchair (2½ months post-surgery), and could roll into the ward lounge to make my own PB toast and tea for breakfast.

For people who haven't experienced it, let me assure you that not being able to eat is far worse than overeating. I dreaded every time they bought the hospital meal trays around, because I knew I'd have to stare at it for an hour or more feeling nauseous until they came and took it away. I am concerned about the weight I gained later on ADT and ARSI, once my appetite came back and before I had recovered enough mobility to exercise, but my joy and gratitude at being able to sit in front of a plate of food and actually *want* to eat it is 100x bigger.