system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: How come humans need around 1,500-2000calories for basic survival of the Body but people suffering from severe anorexia can carry on for years eating a lot less.
gpt
1500 to 2000 calories is what the body needs to remain healthy. Less than that and the body begins cannibalizing non essential things. It starts with fat stores, then it goes to muscles. All in the name of keeping energy supplied to the vital organs. Severe anorexics will consume just enough calories to keep their brain, heart, and lungs functioning but their body will essentially be digesting itself. That's why you'll see malnourished people looking like skeletons with skin stretched over the bones. Their muscles are barely there anymore.