What Is Refeeding Syndrome? Warning Signs & Complications

Known as refeeding syndrome, when individuals who are malnourished begin to eat again, the sudden shift in metabolism can cause rapid and potentially fatal shifts in electrolytes, particularly phosphorus, potassium and magnesium, causing a variety of medical complications. The dangers of this condition highlight the importance of preventative care, refeeding from experienced providers and lab monitoring.

What is Refeeding Syndrome?

Refeeding syndrome is a serious and potentially fatal complication of nutritional rehabilitation. It occurs in severely malnourished patients when a diet with increasing calories is started orally, enterally or parenterally.

The latest definition of refeeding syndrome provided by the American Society for Parenteral and Enteral Nutrition (ASPEN) committee describes refeeding syndrome as a decrease in any one, two or three of serum phosphorus, potassium and/or magnesium levels:¹

• Mild: decrease by 10-20%
• Moderate: decrease by 20-30%
• Severe: decrease by >30% and/or organ dysfunction resulting from a decrease in any of these and/or due to thiamin deficiency

Refeeding syndrome can lead to cardiovascular problems, respiratory failure, seizures and even death.¹ Due to the risks associated with refeeding syndrome, it’s crucial for providers to become familiar with this condition so they can promptly identify the warning signs and prevent its development.

How Does Refeeding Syndrome Happen?

Refeeding syndrome happens when a malnourished patient begins refeeding, usually within five days of restarting or significantly increasing nutrition.¹ Malnourished individuals, whether due to an eating disorder or other conditions, are in a catabolic state – characterized by the breakdown of tissues and organs – due to:

1. A lack of nutritional substrates, including:
   • Depleted energy reserves, such as fatty acids, glycogen and proteins
   • Vitamins
   • Intracellular electrolytes
2. Hormonal changes that occur alongside starvation

Phosphorus is the most important intracellular electrolyte in the context of refeeding syndrome. It is a vital component of adenosine triphosphate (ATP), which all cells need to perform basic functions. When refeeding begins and the body suddenly starts to absorb nutrition, it shifts from a catabolic to an anabolic state (building tissues and organs).

Carbohydrates make up most of the consumed macronutrients, leading to the release of insulin. Insulin has anabolic properties and works to move phosphorus, potassium and glucose into the body's cells, further depleting any remaining phosphorus needed by more active cells and tissues.

The brain, muscles (including the heart and diaphragm) and blood cells are highly dependent on phosphorus, and these tissues can quickly begin to fail.

Symptoms of Refeeding Syndrome

A sudden change in the balance of phosphorus and other electrolytes causes the heart to work harder to manage a higher blood volume, which can cause a variety of different symptoms, including:¹

• Fatigue
• Weakness
• Confusion
• Difficulty breathing
• Nausea & vomiting
• Rhabdomyolysis (muscle break down)
• Hemolysis (rupture of blood cells as they travel in the blood stream)
• Seizures
• Heart failure

Refeeding edema

Another sign of refeeding syndrome is edema, or swelling, of the lower extremities. During refeeding, the body secretes insulin, which causes the kidneys to retain salt and water. This results in swelling of the legs.

Impaired cardiac function can also contribute to refeeding edema.

Who is at Risk for Refeeding Syndrome?

Although there is no single marker to identify which patients will develop refeeding syndrome, the American Society for Parenteral and Enteral Nutrition (ASPEN) has published two sets of criteria for identifying patients at increased risk for refeeding syndrome.

Highest risk patients

According to these guidelines, patients at the highest risk for refeeding syndrome meet one or more of the following criteria:¹

• Body mass index (BMI) under 16 kg/m²
• Weight loss of more than 7.5% in 3 months or >10% in 6 months
• None or negligible oral intake for >7 days or <50% of estimated energy requirement for >5 days during an acute illness or injury or <50% of estimated energy requirement for >1 month
• A blood test that reveals moderately/significantly low levels of phosphorus, potassium or magnesium or normal levels after recent low levels that required significant or multiple-dose supplementation
• Evidence of severe loss of subcutaneous fat
• Evidence of severe loss of muscle mass

Patients with eating disorders

Patients with eating disorders may also have significant risk for refeeding syndrome if they meet two or more of the following criteria:¹

• BMI of 16-18.5 kg/m²
• Weight loss of 5% in 1 month
• Little to no food for the past 5-6 days or <75% of estimated energy requirement for >7 days during an acute illness or injury or <75% of estimated energy requirement for >1 month
• Minimally low levels of potassium, phosphate, or magnesium or normal levels after recent low levels that required minimal or single-dose supplementation
• Evidence of moderate loss of subcutaneous fat
• Evidence of mild or moderate loss of muscle mass during the past 3-6 months
• Little to no food intake for the past 5 or more consecutive days
• A history of alcoholism or drug misuse, including insulin, chemotherapy drugs, diuretics and antacids

Chronic alcohol use, cancer, uncontrolled diabetes or recent surgery may also elevate the risk of developing refeeding syndrome in those with eating disorders.

Refeeding Malnourished Individuals

Nutritional rehabilitation for refeeding syndrome

For severely underweight patients with eating disorders such as anorexia nervosa or avoidant restrictive food intake disorder (ARFID), or those suffering from non-eating disorder-related malnutrition, nutritional rehabilitation is a crucial intervention. Gradually reintroducing calories and an individualized nutrition plan ensure safe and effective refeeding.

Lab monitoring for refeeding syndrome

Refeeding syndrome can be easily avoided with lab monitoring and when under the care of experienced and specialized professionals in refeeding malnourished patients.

“During the refeeding process, food is reintroduced based on metabolic need to address the serious medical complications of malnutrition. However, it is critical that patients be closely monitored by experienced medical professionals during initial refeeding to prevent refeeding syndrome,” explains Allison Nitsch, MD, FACP, CEDS, Physician Team Lead at ACUTE.

How Common is Refeeding Syndrome?

The prevalence of refeeding syndrome is unclear because of different definitions used in studies.^1,2 Although meta-analyses have been conducted, the variation in data makes it hard to determine the true rate of refeeding syndrome.

Is Refeeding Syndrome Fatal?

Yes, refeeding syndrome can be deadly if not properly managed. Hypophosphatemia can severely impair organ function, and organ failure can raise the risk of poor outcomes, including death.

Get Help Safely Refeeding

Refeeding syndrome is a serious condition that requires careful monitoring and nutrition support to prevent. This critical first step in recovery from severe eating disorders and malnutrition relies on medical expertise. If you or a loved one may be at risk, specialized support is available to guide you safely through recovery.

Start now with a free assessment.

References

1. Da Silva, J. S. V., Seres, D. S., Sabino, K., Adams, S. C., Berdahl, G. J., Citty, S. W., Cober, M. P., Evans, D. C., Greaves, J. R., Gura, K. M., Michalski, A., Plogsted, S., Sacks, G. S., Tucker, A. M., Worthington, P., Walker, R. N., & Ayers, P. (2020b). ASPEN Consensus Recommendations for Refeeding Syndrome. Nutrition in Clinical Practice, 35(2), 178–195. https://doi.org/10.1002/ncp.10474
2. Cioffi, I., Ponzo, V., Pellegrini, M., Evangelista, A., Bioletto, F., Ciccone, G., Pasanisi, F., Ghigo, E., & Bo, S. (2021). The incidence of the refeeding syndrome. A systematic review and meta-analyses of literature. Clinical Nutrition, 40(6), 3688–3701. https://doi.org/10.1016/j.clnu.2021.04.023