– Why is it that humans can survive for weeks without food, but if the body goes without food for just a few hours people start to feel uncomfortably hungry?
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Before the modern world, Human body fat is suppose to be a resource for the body to use when there’s an absence of food during hard times, like winter. Fat is just stored energy for later use. Water is more important. 3 days without water/a hydrating liquid, you’ll be dead. Having 31% body fat and a good supply of water, you’ll live for a few weeks.
I think when u go more than a few days without eating your metabolic process changes up and your body goes into a different mode kinda where it burns calories from fat and reserves in the body instead of using gi tract for calorie source. That’s probably a terrible half wrong explanation but it’s the best I can offer I’m sure someone with a science background will have an actual science name for it. But just FYI. I’ve gone almost 2 weeks without eating 8 or 9 of those days I was on iv fluids no water……I was hungry AF the entire time it was miserable at one point I dropped 6.7 lbs over a 24 hr period. Doing nothing but laying in hospitals bed knocked out most of the time.
Biologically speaking, as a species we are still very much prehistoric.
The human species and some offshoots have been around for well over a million years and the anatomically modern human for almost 300,000.
For most of that time food was scarce and we spent most of the time looking for it. History only spans about 20,000 years, so we haven’t yet had time from a evolutionary perspective to evolve away from that biological urge to hunt for food constantly.
Our brains are basically wired to avoid starvation. Some species, snakes for example, have the ability to consume massive amounts of food in one sitting and then can wait for weeks to eat again.
When you eat regularly, your stomach is always ready for food – and when it doesn’t get it, your stomach starts to rumble and growl, basically telling you “I’m hungry, feed me”. When that goes on for a while, it starts to feel uncomfortable as the acids in your stomach start to break down the protective stomach lining (it’s basically a layer of phlegmy stuff that stops the acid from burning a hole through your stomach)
When you go for a long time without food, your body recognises this. So it says to your stomach “You’re not getting any food, so take a rest” and then you start to use up all energy stores your body has, so sugars and fats, and as long as you have water, your body can survive on those fats for a couple of weeks, I think.
Feeding is one of the four fundamental F’s that drive a great deal of animal behavior. Feeding, fleeing, fighting, and reproducing.
Evolution has guven us powerful urges for all four of these, but it has also provided us the ability to store energy for lean times.
Your stomach is like a muscle. You eat it expands to hold the food when its empty it will begin to shrink like letting the air out of an inflated balloon. After a time without food the stomach shrinks to where you dont feel hungry anymore. After say 24-48 hours things start to happen in your body. Your red blood cells need a constant source of energy. When they begin to starve they send out emergency signals to your liver. You liver responds by releasing “glucagon” to feed the red blood cells. But your liver only has so much emergency supply of it so it will break down the bodies fat stores as an energy source. I know this because I am diabetic, when I was diagnosed 12 yrs ago my doctor referred me to diabetes educator”
You do not feel hungry when you need to eat, tired when you need to sleep, bladderful when you need to urinate, etc.
Your body does not wait until you need to do something to trigger you to do it. It wants you to do things regularly and conveniently to avoid a crisis.
Humans evolved as hunter/gatherers who needed a long time to get the food they needed to survive. So we feel hungry when we do not need to eat but an eat, so that we have time to get the food to eat.
Imagine it took 8 hours to get a meal together instead of just going to your kitchen and eating in 5 minutes. You would want to feel hungry 8 hours before you needed to eat (at least).
I fast every Saturdays. Only the first Saturday was somewhat uncomfortable, now I don’t even feel slightly hungry throughout the fast.
If you aren’t painfully thin, your body probably has enough fat reserves to last you a good long while, it’s just that they don’t get tapped into unless all the more readily available sources (glucose, carbs) are exhausted.
Once the body starts to tap into the fat reverses, boom, no need for hunger.
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