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Refeeding syndrome and anorexia

Anorexia nervosa (AN) is a dangerous eating disorder that requires specialized care and treatment to overcome. But sometimes, the initial phases of recovery can be just as dangerous as the condition itself.

Refeeding syndrome is a serious complication that can arise when someone with severe AN starts eating more food again. But with careful attention and the right kind of care, it's possible for someone to recover from anorexia nervosa without suffering this potentially deadly condition.

 minutes read
Last updated on 
November 1, 2023
November 1, 2023
Refeeding syndrome and anorexia
In this article

What is refeeding syndrome? 

Refeeding syndrome describes a number of potentially serious internal changes that can occur when an individual who has been starving or malnourished for a long time re-introduces too many calories to their diet too quickly.1

There is no official definition of refeeding syndrome, though the condition is tied to fluid and electrolyte imbalances, changes in metabolism, and changes in levels of phosphate, potassium, and magnesium in the body.2

Refeeding syndrome can be triggered by feeding that is done either orally or intravenously.1 In a worst case scenario, it can lead to heart or kidney failure, but it can be avoided, with someone successfully regaining weight, when the refeeding process is managed by medical experts.2

Refeeding syndrome must be managed by medical experts.

What causes refeeding syndrome with anorexia

Things change fundamentally inside the body when someone doesn't eat or excessively fasts for a long time.

Normally, when someone is partaking in a healthy diet, the body gets most of its energy from glucose, a form of sugar derived from food and especially carbohydrates. But when someone is starved, malnourished, or fasting for prolonged periods of time, the body must turn to other sources for energy, including the protein and fatty acids found in the muscles and other parts of the body.1

When the body makes this internal switch, it leads to a cascade of effects, with hormone levels, metabolic rate, and other internal functions changing to address these developments. Those changes will largely remain in place so long as the person is starving or malnourished. But once the body begins receiving more food again on a regular basis, these processes shift again.2

More carbohydrates and calories lead to higher levels of glucose and insulin in the blood, which, in turn, impact potassium, magnesium, and phosphate levels. When these fluctuations happen too quickly, it can create an imbalance of these electrolytes and fluids, and this is what brings on many of the dangerous health complications related to refeeding syndrome.1

Refeeding syndrome symptoms

While researchers have yet to agree on an official definition of refeeding syndrome, it's generally agreed that the condition can be very dangerous. Refeeding syndrome symptoms impact nearly every system and organ in the body, including the heart, the kidneys, the endocrine system, the gastrointestinal system, and the pulmonary system.2

All told, the shifting hormone and electrolyte levels involved in refeeding syndrome have been connected with:2

  • Muscle weakness
  • Trouble breathing
  • Seizures
  • Coma
  • Cardiomyopathy (heart muscle weakness)
  • Nausea and vomiting
  • Tremors
  • Muscle spasms
  • Fatigue
  • Severe constipation
  • Delirium
  • Vision problems
  • Hypothermia
  • Amnesia
  • Fluid in the lungs
  • Kidney dysfunction
  • Headache
  • Blurred vision
  • Congestive cardiac failure

Of all the imbalances caused by refeeding, shifting levels of phosphorus are perhaps the most problematic. This issue of developing refeeding syndrome is linked to a number of heart problems, including arrhythmias, or irregular heartbeat, which can be fatal. It can also lead to respiratory failure. And the long periods of starvation experienced with severe anorexia nervosa can work to deplete phosphorus levels even more, making the refeeding process even more dangerous. (3)

Refeeding syndrome and anorexia

How to prevent refeeding syndrome

Since refeeding syndrome is largely undefined, and everyone responds to treatment and illness differently, there is ongoing debate about how to best avoid refeeding syndrome.

Illustrating this point, one study found that nutritional supplements—particularly supplements of potassium, magnesium, and phosphate—were effective at preventing refeeding syndrome, but the most effective amount, method, and duration of delivering these supplements varied between refeeding patients.4

There's also uncertainty around the ideal caloric intake patients with anorexia nervosa need to recover. Older guidelines recommended starting someone at no more than 50% of daily energy requirements, with calories being raised to normal levels over the course of four to ten days.1 But others have argued against these guidelines, saying they ultimately work to prolong underfeeding.5

Another study found that lower calorie refeeding was too conservative for mild- to moderately-malnourished patients, and starting with a higher caloric intake in these cases did not present a higher risk for refeeding syndrome. But the same study also concluded that there was no reason to change the recommendation for patients at extreme low body weight or otherwise higher risk for developing refeeding syndrome.6

Treating refeeding syndrome

Due to all the nuance and complication involved in detecting and preventing refeeding syndrome, the process should always be done under the care of medical professionals within a hospital setting. Treating anorexia refeeding syndrome at home is a dangerous and potentially deadly idea.

Generally, patients coming into the hospital for severe anorexia nervosa are evaluated for their potential risk of refeeding syndrome, including the number of consecutive days they've gone without food or have been undernourished. Doctors may base refeeding and nutrition therapy recommendations around these potential risk factors.5

If a patient goes on to develop refeeding syndrome, there are a number of precautions that are usually followed. Restoring hydration is usually the first step, and fluid balance and weight are carefully monitored. Cardiac monitoring is also common, and electrolyte supplements, particularly potassium supplements, may be altered.5

Hypothermia and sepsis also may occur, and these issues are treated immediately if detected.5 Overall, though, doctors and the hospital's nutrition support team will continually monitor a patient's health, correct electrolyte imbalances, and attempt to balance the importance of refeeding against the dangers of underfeeding or feeding too much too fast.

Finding help for anorexia nervosa

Refeeding syndrome is one of the most dangerous aspects of recovering from anorexia nervosa. However, if done with careful medical supervision and adequate support, refeeding can be done safely and can be an essential first step toward recovery.

Once someone has established medical stability, they can begin working on the deeper psychological and emotional aspects that drive or maintain their condition. At this point, Within Health may be able to help.

Getting help at Within

Our multidisciplinary team understands that AN is a physical, mental, and emotional health issue, and will develop a personalized treatment plan for you or your loved one to cater to your individual needs.

Reach out to our team at Within Health today to learn more about our virtual care programs for anorexia nervosa.

Get help today

Disclaimer about "overeating": Within Health hesitatingly uses the word "overeating" because it is the term currently associated with this condition in society, however, we believe it inherently overlooks the various psychological aspects of this condition which are often interconnected with internalized diet culture, and a restrictive mindset about food. For the remainder of this piece, we will therefore be putting "overeating" in quotations to recognize that the diagnosis itself pathologizes behavior that is potentially hardwired and adaptive to a restrictive mindset.

Disclaimer about weight loss drugs: Within does not endorse the use of any weight loss drug or behavior and seeks to provide education on the insidious nature of diet culture. We understand the complex nature of disordered eating and eating disorders and strongly encourage anyone engaging in these behaviors to reach out for help as soon as possible. No statement should be taken as healthcare advice. All healthcare decisions should be made with your individual healthcare provider.


  1. Mehanna, H. M., Moledina, J., & Travis, J. (2008). Refeeding syndrome: what it is, and how to prevent and treat it. BMJ, 336(7659), 1495–1498.
  2. Refeeding syndrome. (n.d.). Cleveland Clinic. Accessed October 2023. 
  3. Persaud-Sharma, D., Saha, S., Trippensee, A.W. (2022). Refeeding Syndrome. StatPearls. Accessed October 2023. 
  4. Gallagher, D., Parker, A., Samavat, H., & Zelig, R. (2022). Prophylactic supplementation of phosphate, magnesium, and potassium for the prevention of refeeding syndrome in hospitalized individuals with anorexia nervosa. Nutrition in Clinical Practice, 37(2),  328–343.
  5. De Silva, A., & Nightingale, J. M. D. (2019). Refeeding syndrome : physiological background and practical management. Frontline Gastroenterology, 11(5), 404–409.
  6. Garber, A. K., Sawyer, S. M., Golden, N. H., Guarda, A. S., Katzman, D. K., Kohn, M. R., Le Grange, D., Madden, S., Whitelaw, M., & Redgrave, G. W. (2016). A systematic review of approaches to refeeding in patients with anorexia nervosa. The International Journal of Eating Disorders, 49(3), 293–310.


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