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
Fat may provide energy, but it does not provide all your nutritional needs.
You *can* live on fat and vitamin supplements (and water) pretty much indefinitely. As there was one guy who didn’t eat for 200+ days. And came out the other end just fine, he had some trouble adjusting back to food, but no long term health complications.
But it’s also incredibly unpleasant. You’re not supposed to *want* to live off fat reserves. Going back to hunter gatherer times your fat reserves were what kept you alive over winter or in the event you got hurt/sick and couldn’t hunt for a while. Evolutionarily, you’re not supposed to be losing fat. It means you’re failing at feeding yourself. But inevitably there will be times that you’d go hungry, so fat reserves.
That food scarcity is hardly an issue in our modern time, and so that’s why it’s so hard to overcome our nature and keep ourselves at a calorie deficit.
Latest Answers