Fasting and Re-Feeding Syndrome

Fasting and re-feeding syndrome has received an increasing amount of attention in medical literature over the last decade, and is more often now referred to as refeeding syndrome, after the initial observation of this phenomenon by David Katan in the early 1980s. The syndrome was initially described in patients who fasted for more than 23 hours and re-fed (that is, fed after the first day of the fast) without the use of intravenous fluids.

Fasting and re-feeding syndrome is a catch-all diagnosis that remains a mystery to the medical community. Although the syndrome is punctuated by episodes of severe weight loss, frequent changes in weight, and the rapid cycle of eating, fasting, and then re-feeding, no one has ever pinpointed the exact cause for the syndrome.

Your body has a natural clock. It is designed to maintain a constant internal body temperature and metabolic rate. When the temperature in your body rises above that set point, your body will try to find a way to lower it. The most common way is to increase the amount of heart rate. However, the body can’t maintain this constant rate indefinitely, so it will eventually call on the body’s stores of energy (calories) to maintain the internal baseline. Unfortunately, the body only has so many stores, so when they are used up, some other mechanism must be used to replace them. That mechanism is the dreaded fasting and re-feeding syndrome.


Recurrent hunger syndrome is one of the most severe consequences of chronic food restriction, but it is thankfully uncommon. During World War II, extremely malnourished Americans in Japanese prisoner of war camps were the first to be diagnosed with overnutrition complications. It’s also been used to treat alcoholics and those with long-term anorexia nervosa. If you’re attempting to fast for a lengthy period of time – typically more than 5-10 days at a time – you should be aware of these symptoms.

Refeeding is the process of gradually resuming eating after a lengthy time of fasting. Fasting, in particular, may assist to decrease the chances of this problem occurring. Refeeding syndrome and refeeding edema are the two major syndromes.

David Blaine, a magician, completed a 44-day water fast in 2003. Even though he was in the limelight the whole time, opinions differ on whether or not he cheated. The physicians collected all the measures they could while he was in the hospital. His body mass index (BMI) fell from 29 to 21.6 after he shed 24.5 kg (25 percent of his total weight). The levels of glucose and cholesterol in my blood were both normal. The amount of free fatty acids was high (which is to be expected in a situation of famine).


He experienced overeating syndrome and bloating when he resumed eating. The amount of phosphorus in the blood has significantly decreased. He had to remain in the hospital for a few days as a precaution and get intravenous phosphorus supplements. He was well after that.

Syndrome of the dessert


The re-feeding syndrome is a potentially life-threatening fluid and electrolyte redistribution that may occur in malnourished individuals. Malnutrition is the important term here. Hypophosphatemia, or a low amount of phosphorus in the blood, is the most common symptom of this illness. Reduced blood potassium, calcium, and magnesium levels, on the other hand, may have a role.

The skeleton contains around 80% of the phosphorus in our bodies, while the soft tissues contain the remaining 20%. Almost majority of the phosphorus is contained inside the cell, not in the blood. Phosphorus levels in the blood are carefully monitored, and if they are too high or too low, they may cause serious issues. Because the typical daily phosphorus intake is 1 g/day, these disorders often need many months of starvation before they manifest. Phosphorus may be found in protein-rich meals, cereals, and nuts. Phosphorus is absorbed mostly in the small intestine, where 60-70 percent of it is absorbed.

Our bones contain the majority of the calcium, phosphorus, and magnesium in our bodies. If the body need additional intracellular ions, it will take them from bone stores.


Phosphorus levels in the blood remain normal in instances of chronic malnutrition, and the shortfall is made up by the bones. As the acute starvation of Japanese prisoners of war during World War II shown, this may take a long period. It was proven during World War I. Because the daily phosphorus intake is 1 g, a severe phosphorus shortage in the body would require hundreds of days without phosphorus intake. Because phosphorus is present in nearly all meals in some form or another, the refeeding syndrome is usually invariably associated with malnutrition (underweight, anorexia nervosa, alcoholism).

Insulin and supplementation

Following the delivery of meals, particularly carbohydrate-rich diet, eating difficulties may develop. During the eating phase, insulin and other hormones are triggered. Important intracellular ions (phosphorus, potassium, calcium, and magnesium) are moved into the cells as a result of this. This is exacerbated owing to the overall depletion of bodily reserves, and too few of these ions remain in the blood. The primary symptoms of overeating syndrome result from this, some of which may be deadly in rare instances.

Phosphorus is required for energy generation in all cells. Because the fundamental unit of energy (ATP) includes three phosphorus molecules, a significant phosphorus deficiency may result in the de-energization of the whole body. When the serum phosphorus level goes below 0.30 mmol/L, this happens. As the diaphragm (the big muscle that supports the lungs) weakens, it causes muscular weakness and trouble breathing. There have been reports of direct muscle damage (rhabdomyolysis) and heart dysfunction (cardiomyopathy).

Magnesium shortage may induce seizures, disorientation, tremors, tetany, and convulsions since it is a cofactor in most of the body’s enzyme systems. Cardiac arrhythmias, including the typical torsades de point pattern, are also discussed. The majority of orally consumed magnesium (about 70%) is not absorbed and is expelled unaltered in the feces. Potassium may also move into cells, resulting in dangerously low blood potassium levels. It may also cause irregular heart rhythms or even cardiac arrest.

Insulin promotes glycogen, lipid, and protein synthesis, which necessitates a variety of ions, including phosphorus, magnesium, and cofactors like thiamine. Insulin increases place a tremendous burden on the body’s already low phosphorous stores. In reality, all of these intracellular ions’ stores are severely depleted, and when the signal for replenishment is provided, too much phosphorus is taken from the blood, resulting in a phosphorus level that is excessively low.


Refeeding syndrome and malnutrition


As you can see, severe and chronic malnutrition is one of the major symptoms of the overeating syndrome. Is this something that happens frequently? A study of over 10,000 hospitalized patients showed a 0.43 percent incidence rate. Even though they are the sickest of the sick, they are nonetheless uncommon. This is an exaggeration since it includes diabetic ketoacidosis, which is caused by a totally different process. What are the major categories affected by this disease? Alcoholism and severe starvation.

Long-term malnutrition is the most important risk factor for the development of refeeding syndrome. Most individuals who utilize fasting as a therapeutic technique haven’t skipped a meal in over 25 years! That isn’t the position we’re in right now.

It’s essential to note, however, that individuals who are extremely underweight or malnourished should not fast. This is significant because refeeding syndrome is more likely to develop in the presence of starvation (uncontrolled and forced food restriction) or emaciation (starvation resulting in severe malnutrition) than in the absence of starvation (controlled and voluntary food restriction).

Vitamin deficits have also been reported, primarily as a consequence of starvation over time. Thiamine is the most significant of them, since it is a necessary cofactor for carbohydrate metabolism. It is most often seen in alcoholics with Wernicke’s encephalopathy syndrome (ataxia, confusion, and visual abnormalities) and Korsakoff’s syndrome (ataxia, confusion, and visual disturbances) (memory loss and confusion).

Confabulation is a symptom in which a person’s short-term memory is completely absent. As a result of their lack of memory, they make things up as they go along. The goal is not to deceive. If malnutrition is an issue, don’t starve yourself; instead, take a generic multivitamin.

Nutritional oedema that occurs on a regular basis

Insulin causes the kidneys’ proximal tubules to reabsorb salt and water. Salt and water retention are caused by high insulin levels. Low insulin levels cause the kidneys to lose salt and water. Over 30 years ago, this was clearly explained.

Insulin levels decrease dramatically while fasting. This may result in a loss of salt and water. According to George Cahill’s essay Starvation, up to 10 kg of water weight may be lost in certain severe instances. Low insulin levels prevent the body from retaining salt and fluids. When food is eaten again, particularly carbs, insulin levels rise and the kidneys begin to retain a lot of salt and water. It’s possible that sodium excretion will drop to less than 1 mEq/day.

Significant edema may develop in severe instances. If your feet and legs swell excessively, this may happen. In individuals with heart problems, fluid buildup in the lungs may produce congestion. This condition is known as post-natal swelling. Fortunately, when administered properly in the clinic, this is an uncommon occurrence. Fasting is a great therapeutic technique for overeaters, however it is not recommended for malnourished individuals.



Treatment begins with prevention. The people who are most prone to develop refeeding syndrome are mentioned in Box 3. Of course, the goal isn’t to starve a hungry person, but that should be apparent by now.

The most essential treatment technique, apart from prevention, is to begin eating carefully. This typically involves feeding at half the necessary rate or less, with a gradual increase in pace if no issues are discovered. The customary admonition to break the fast with care reflects this. Because of the duration of Lent, this is even more essential. We’ve observed a lot of folks overeat once Lent is done. When most individuals eat, they experience stomach discomfort, but it typically subsides soon. I’ve never seen or handled refeeding syndrome, and I pray I never will.

During Blaine’s shift, what happened?


There were several discrepancies between Blaine’s fasting and the MDI’s fasting. At first, it was only a water station. We usually only deploy them in severe situations. Bone broth is consumed while fasting, and although it is not strictly fasting, it supplies phosphorus, other proteins, and electrolytes. Overeating syndrome is less likely to occur as a result of this.

Second, you can see Blaine is encased in plexiglass for the length of the article. He is unable to carry out his normal tasks and has not risen from his bed for 44 days. It’s not just a job. His muscles and bones deteriorate dramatically throughout this period. He dropped a lot more than simply weight. He lost a lot of muscle and bone mass, but it wasn’t from hunger. That’s because he was imprisoned for 44 days in a coffin. This is not something that everyone should do.

During Lent, we encourage our patients to keep up with their regular routines, particularly their exercise routine. This helps to keep their muscles and bones in good shape.

Feeding problems are rare. This is not a problem for short term fasting (<36 hours). So, if you’re worried, short intermittent fasting is still safe. For prolonged fasting, a general multivitamin or a change in fasting schedule (e.g. bone broth instead of fasting exclusively with water) may help. Avoid fasting if you are malnourished.

Jason Fung, Ph.D.

Fasting and re-feeding syndrome is a condition that can cause the physical symptoms of starvation and the psychological symptoms of hunger. It is a medical emergency that can lead to death. It’s a serious problem, but many people aren’t aware of its existence.. Read more about refeeding syndrome bloods and let us know what you think.

Frequently Asked Questions

How long does refeed syndrome last?

The length of time for refeed syndrome is dependent on the individual. It can range from a few days to a few weeks.

What do you monitor for refeeding syndrome?

I monitor for refeeding syndrome by checking the blood glucose levels of my patients.

When should I worry about refeeding syndrome?

If you are experiencing symptoms of refeeding syndrome, such as nausea, vomiting, diarrhea, or abdominal pain, then you should seek medical attention.

About Vaibhav Sharda

Vaibhav Sharda

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