Word is getting out (finally!) about the therapeutic benefits of fasting, and more and more people are experimenting with periods without food. Along with that interest comes a scary term that you’ve either heard by now or you will hear: refeeding syndrome. 

It sounds dramatic, and in true cases it can be. But here’s the key: real refeeding syndrome is rare in healthy people doing controlled fasting. It is very different from the mild, uncomfortable symptoms some people feel when they break a fast. 

Let’s look at the difference, and how to know when refeeding syndrome really is an issue. 

What is refeeding syndrome?

Refeeding syndrome is a serious medical condition that can happen when you reintroduce food after prolonged starvation or severe malnutrition. 

It was first identified in prisoners of war after World War II and is still most common in hospital settings today. It can occur in people with eating disorders, or even in long-term illnesses. 

Here’s the basic breakdown of what happens: 

When someone has been undernourished for a long time, their body adapts. Insulin levels stay low, and the body mostly runs on stored fat. 

When food — especially carbohydrates — is introduced, insulin rises quickly, and tells the cells to open up and take glucose in. But the problem is, glucose does not go in alone. It pulls vital minerals with it, including magnesium, phosphorus, and potassium. 

If your mineral levels are already low, and those levels drop too fast, it can affect the heart, muscles, nerves, and even breathing. Severe cases can be life-threatening. 

That is true refeeding syndrome. 

Symptoms of true refeeding syndrome (again, rare) can include:

• Nausea and vomiting

• Pins and needles tingling 

• Edema 

• Confusion

• Low blood pressure

• Seizures

• Breathing problems

• Changes in heart rhythm 

Why phosphorus matters so much

Phosphorus is critical for making ATP (adenosine triphosphate), which is the energy currency of your cells. Without enough phosphorus, your body cannot properly produce energy. 

During starvation (and very long extended fasts can technically be considered starvation), total body phosphorus becomes depleted. When refeeding begins, the cells suddenly demand more, and if blood levels fall too low, serious complications can happen. 

This is why phosphorus is central in preventing true refeeding syndrome. 

What most fasters actually experience

Don’t let all that scare you. Let’s talk about what most healthy adults experience after a controlled fast, especially if they break with carbohydrates. You might feel:

• Bloating

• Puffy hands or face

• Temporary weight gain from water

• Fatigue

• Headache

• Mild weakness

This happens because insulin rises when you eat again, which tells the kidneys to hold onto sodium. Sodium holds onto water. So you retain fluid. 

It can feel uncomfortable, but it is not the same thing as medical refeeding syndrome. 

It’s a temporary shift and usually resolves within a day or two. 

How to reduce risk and feel good during a refeed

• First, if you’re really concerned about refeeding issues, avoid extended fasts. The longer you fast, the more cautious you need to be when you reintroduce food. You can still get all the benefits that fasting offers with Intermittent Fasting. More is not always better. 

If you do prefer Extended Fasting, take breaks between fasts to focus on nutrition. And fast under the guidance of your healthcare provider, especially important if you have medical conditions or you are on medications. 

• Second, always break your fast gently. Follow proper refeeding guidelines. Start with bone broth and slowly add soft, easily digested foods. Avoid simple carbohydrates which will cause your body to hang onto more water.

• Third, support your body with key nutrients, both during the fast and during the refeed. Don’t skip electrolytes. And if you fast for 14 days or more, start our Fasting Refeed formula at least 30 minutes prior to breaking your fast. 

Our Fasting Refeed contains phosphorus, and B vitamins. 

B vitamins are important during refeeding. Thiamine helps your body process carbohydrates safely. In hospitals, thiamine is often given before refeeding malnourished patients for this reason. 

True refeeding syndrome doesn’t happen often

The risk of refeeding syndrome is low, but that doesn’t mean that refeeding should be done carelessly. 

When you fast, do it intentionally. And when you eat again, nourish your body with care.