eli5: why is it so difficult to go a week without eating when we have 10s of thousands of calories worth of body fat?

Question

eli5: why is it so difficult to go a week without eating when we have 10s of thousands of calories worth of body fat?

In: 89

Answer 1

In simpler term, our bodies are good at storing fat, reluctant to let it go, and lousy at actually using them. We can survive on less food + body fat, but not on body fat alone.

In times of absolute starvation, our bodies use fat in such an inefficient way that, both the quality of the converted energy from fat, and the quantity of fat that gets converted, are lousy at best. We also need other nutrients that body fat simply can’t provide.