Eli5: how are “feast and famine” animals able to eat massive amounts of food after not eating for months or years, but humans will get re-feeding syndrome if eating a lot after a fast?
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Real answer: When you’re starving your body greatly decreases how much protein and stuff cells make, but there are still some essential things that they constantly need to make to survive. Since you aren’t getting anything from diet, this depletes the amounts of electrolytes and minerals and cells – they get used up making the essential stuff. While you’re starving your body is in full on conservation mode so you aren’t making any insulin. As soon as you eat food your body responds by making insulin again, and starts to store glucose, and this all tells your cells to resume normal production. However your cells still have very low concentrations of some minerals and electrolytes – specifically you’re worried about magnesium, potassium, and maybe phosphates. The cells that are now producing lots of proteins again now need to get these molecules from somewhere. They can take take them in from the blood, but that makes the concentration in your blood – we call it serum concentration – rapidly drop. Your body relies on having a consistent concentration of these things in your blood; as they drop you get seizures, heart arrhythmias or total heart failure, comas, etc.
Real answer: When you’re starving your body greatly decreases how much protein and stuff cells make, but there are still some essential things that they constantly need to make to survive. Since you aren’t getting anything from diet, this depletes the amounts of electrolytes and minerals and cells – they get used up making the essential stuff. While you’re starving your body is in full on conservation mode so you aren’t making any insulin. As soon as you eat food your body responds by making insulin again, and starts to store glucose, and this all tells your cells to resume normal production. However your cells still have very low concentrations of some minerals and electrolytes – specifically you’re worried about magnesium, potassium, and maybe phosphates. The cells that are now producing lots of proteins again now need to get these molecules from somewhere. They can take take them in from the blood, but that makes the concentration in your blood – we call it serum concentration – rapidly drop. Your body relies on having a consistent concentration of these things in your blood; as they drop you get seizures, heart arrhythmias or total heart failure, comas, etc.
Real answer: When you’re starving your body greatly decreases how much protein and stuff cells make, but there are still some essential things that they constantly need to make to survive. Since you aren’t getting anything from diet, this depletes the amounts of electrolytes and minerals and cells – they get used up making the essential stuff. While you’re starving your body is in full on conservation mode so you aren’t making any insulin. As soon as you eat food your body responds by making insulin again, and starts to store glucose, and this all tells your cells to resume normal production. However your cells still have very low concentrations of some minerals and electrolytes – specifically you’re worried about magnesium, potassium, and maybe phosphates. The cells that are now producing lots of proteins again now need to get these molecules from somewhere. They can take take them in from the blood, but that makes the concentration in your blood – we call it serum concentration – rapidly drop. Your body relies on having a consistent concentration of these things in your blood; as they drop you get seizures, heart arrhythmias or total heart failure, comas, etc.
Some mammals are adapted to hibernation periods where their metabolic rate slows to a crawl, and kcal energy and water demands become far lower. In addition, when they rise from hibernation, they don’t immediately pig out, they start small and gradually wake their normal rhythm.
The main dangers of refeeding syndrome is in the shock of large amounts of food/drink when having none for at least a week(if you survived the no water part, which is unlikely). Its similar to dependent alcoholics that decide to go cold turkey. Since their brain has been flooded with alcohol that blocks many normal chemical signals, the brain has increased output of those chemicals in order to try and ‘punch through’ the alcohol. Suddenly removing this wall means that punch becomes deadly.
I work in catering for a hospital, and am well versed with specific diets for abdominal/surgical wards for post-op patients. Their surgeons will delicately avoid troubling their gut by sticking them on ‘clear fluid only’ diets(which doesn’t include milk btw) before graduating them up to ‘full fluids’ and then perhaps ‘low residue/low fiber’ after that. Slow and steady.
Some mammals are adapted to hibernation periods where their metabolic rate slows to a crawl, and kcal energy and water demands become far lower. In addition, when they rise from hibernation, they don’t immediately pig out, they start small and gradually wake their normal rhythm.
The main dangers of refeeding syndrome is in the shock of large amounts of food/drink when having none for at least a week(if you survived the no water part, which is unlikely). Its similar to dependent alcoholics that decide to go cold turkey. Since their brain has been flooded with alcohol that blocks many normal chemical signals, the brain has increased output of those chemicals in order to try and ‘punch through’ the alcohol. Suddenly removing this wall means that punch becomes deadly.
I work in catering for a hospital, and am well versed with specific diets for abdominal/surgical wards for post-op patients. Their surgeons will delicately avoid troubling their gut by sticking them on ‘clear fluid only’ diets(which doesn’t include milk btw) before graduating them up to ‘full fluids’ and then perhaps ‘low residue/low fiber’ after that. Slow and steady.
Some mammals are adapted to hibernation periods where their metabolic rate slows to a crawl, and kcal energy and water demands become far lower. In addition, when they rise from hibernation, they don’t immediately pig out, they start small and gradually wake their normal rhythm.
The main dangers of refeeding syndrome is in the shock of large amounts of food/drink when having none for at least a week(if you survived the no water part, which is unlikely). Its similar to dependent alcoholics that decide to go cold turkey. Since their brain has been flooded with alcohol that blocks many normal chemical signals, the brain has increased output of those chemicals in order to try and ‘punch through’ the alcohol. Suddenly removing this wall means that punch becomes deadly.
I work in catering for a hospital, and am well versed with specific diets for abdominal/surgical wards for post-op patients. Their surgeons will delicately avoid troubling their gut by sticking them on ‘clear fluid only’ diets(which doesn’t include milk btw) before graduating them up to ‘full fluids’ and then perhaps ‘low residue/low fiber’ after that. Slow and steady.
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