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
A lot of these comments are about minerals, vitamins, and fat but realistically in just one week none of that really matters yet(ish).
Physiologically the first 2 or 3 days you’ll be pretty hungry because ghrelin which is a hormone your body produces that triggers hunger is pretty high. After 2 or 3 days it’ll subside and you won’t be that hungry.
Near the end of a 7 day fast you might get lightheaded, feel weak, low energy etc as you probably aren’t used to running on ketones instead of glycogen. It’s not harmful per se but it feels different and it may make you uncomfortable enough to eat.
And there is the psychological component. You are probably pretty used to eating or thinking about eating it’s a habit. Suddenly stopping a habit is not easy.
In other words in a short seven day water fast minerals, vitamins, fat etc don’t really have anything to do with why it’s difficult.
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.
Actually I’m pretty sure the main reason is you’ll develop organ failures if you aren’t eating regularly despite how fat you may be
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