A lot of things about your body changes when you're extremely tired. I don't have anything specific to link - it's just my own personal experience and what the

A lot of things about your body changes when you're extremely tired. I don't have anything specific to link - it's just my own personal experience and what the doctor said. In my own case, I had to eat much more than I theoretically should because my body wasn't able to process the food as well as it should (less than 50% of usual efficiency). And yet I was fat - not obese, but definitely not thin. The body redirected some of my food to storage even though I didn't have enough energy (glucose etc) as measured by blood screening. And it didn't use the reserves properly when I stopped eating.