My grandmother survived Hitler's camps and Stalin's holodomor starvation campaign. She always said the fat people were the first to starve, often while still fat. Or they were killed right away for not keeping up with the work load. The skeleton people you see in photos are unlikely to be formerly fat people.
I think it's because the stored fat in your body doesn't provide all the nutrients one needs to live. That's why you always burn muscle while starving. Eventually your heart will get eaten away. And if you are fat, the heart will fail much earlier.
Lesson learned - being fat it not a substitute for storing food.
If only we were bears.