How to Break a Water Fast

So I’ve been pretty vocal about my keen interest in water fasting and the ketogenic diet. And while the two are not at all the same, they are often practiced together. I talk more about the ketogenic lifestyle and share my personal experience specifically in this post. So fasting is pretty self-explanatory, but how do you break a water fast without sabotaging yourself?

Why do People Fast?

Many people fast throughout the year for a variety of reasons. Some fast for religious reasons, while others are after the health benefits. Fasting is a great way to control blood sugar and insulin levels { *, *}, reverse aging {*, *} and protect against aging-related diseases {*}, improve gut health {*} or reach weight loss goals and maintain body weight {*, *}.

What to Eat After a Water Fast?

Whether you’ve been fasting for 24 hours or 7 days or more, you might wonder what is the best way to break your water fast. And if you’re looking for a quick guide on what to eat after fasting, you can skip to my refeed plan below, or keep on reading if you’re into the details.

Skip down to read more about the fasting protocol I’m attempting this year and why.

How to End a Water Fast Under 36 Hours?

Generally speaking, a fast lasting less than 36 hours, should not require any special consideration. Obviously do not go binging on sugar or processed anything. Otherwise, do your normal thing and you should be just fine.

What Happens in a Prolonged Fast?

Eating after prolonged water fast does take some planning, however. After about 3 days of water fasting, your body shuts down most of the normal processes, runs out of stored glycogen, and starts using its own tissues like fat and muscle (as well as other tissues) for energy by way of ketogenesis.

Ketogenesis is a process by which your body converts ketogenic amino acids from protein and fatty acids into ketones to be used as energy by many organs and tissues in your body.

When in a fasted or malnourished state, this process is called autophagy. During autophagy, your body is literally eating itself to sustain itself. While it sounds scary, it’s actually a biological adaptation to help clear and repair ourselves from the inside out.

What are the Benefits of Fasting for Prolonged Periods?

The process of autophagy is controlled by AMPK (aka AMP kinase protein) and mTOR (mammalian target of rapamycin). All very complicated stuff…but the long and short of it is this:

AMPK is what activates autophagy by sensing that there is not enough energy influx through your diet. By up-regulating AMPK through fasting, you, in turn, downregulate mTOR activity {*}.

Decreasing mTOR activity is a good thing because increased mTOR activity has been linked to:

• increased aging
• the proliferation of cancer cells
• brain disorders including autism, Alzheimer’s disease 
• potentially some systemic autoimmune diseases.

An increase in AMPK also induces fat oxidation and decreases inflammation throughout the body {*}.

Fasting Complications to Consider

One quite serious, though very rare, complication to consider when introducing food is the refeeding syndrome. The refeeding syndrome is a very rare condition that can be fatal if not carefully monitored. Thankfully it is indeed very rare and mainly observed in severe cases of malnutrition.

Refeeding Syndrome

After a period of extended fasting, without supplementation, your magnesium, potassium, and phosphate stores are very low. As you start consuming food again and your body starts processing macronutrients, especially carbohydrates, your body requires those same minerals to process the food. This can result in a large drop in blood potassium levels and thus lead to serious complications. So anyone at risk should be monitored by a doctor.{*}

Temporary Insulin Resistance After Fasting

It is important to note that after prolonged fasting, similarly to when you stay on a ketogenic diet for extended periods of time, your body is temporarily more insulin resistant when you introduce sugar (a.k.a. glucose). This adaptation actually makes sense if you think about what happens to glucose production and consumption during a fast.

Contrary to what many think, glucose is still produced in a fasted state, though in much smaller amounts, by your liver. This occurs through a process called gluconeogenesis as the liver converts amino acids into glucose. The glucose is shuttled to several organs, but in large part to the brain.

In fact, in a fasted state, glucose from gluconeogenesis accounts for roughly 30-40% of total brain energy consumption. Because of the very limited supply of this glucose, it makes sense that your body would be less sensitive to insulin which would normally shuttle blood glucose to the muscle tissues and the liver. Insulin secretion is definitely reduced in a fasted state {*, *}.

This is why it is a good idea to avoid starches and foods high in carbohydrates immediately after fasting. Instead, you should focus on cooked fibrous low-carb vegetables. Cooking breaks down some of the fiber and makes these vegetables a bit easier to digest. But whatever you do, please do not go and eat a piece of your kid’s cake. That just won’t feel good. Take my word for it.

What to Eat After an Extended Water Fast

During longer fasting periods, your body shuts down many processes including digestion. Introducing solid food right away may be difficult on your body. That’s why the common recommendation post fasting is to start your refeeding process with a simple liquid like bone broth and other easy to digest foods.

Bone broth is one of the best foods to eat after fasting as it is rich in amino acids, including essential amino acids. Your body needs these to start rebuilding all organs and tissues. Once you can tolerate that well, you can start adding small amounts of cooked fibrous vegetables. These will provide your body with glycogen and fiber.

Clean carbohydrates, when ingested together with amino acids, help kick off the rebuilding process. The fiber in the vegetables also helps get your digestive systems going.

You should be able to handle a small meal after 3-4 days, but if you’ve been fasting for over that, you might want to start with some beef broth instead and gauge how you feel.

My personal favorite meal to break a fast is with some lean protein like salmon and fibrous vegetables like broccoli. The salmon is a great source of essential amino acids to help turn off autophagy.

What About Fruit And Vegetable Juices?

Slight insulin resistance discussed above is also the reason I do not recommend fruit and vegetable juices as the best way to break a fast. They do not contain any fiber, yet tend to be quite high in sugar. Since your body has not had any sugar, these will likely generate a spike both in blood glucose and insulin levels. In addition, nutrients from fruits and vegetables are fat-soluble. If you consume them without any fats, you won’t absorb much of those nutrients and vitamins you were expecting anyways.

Why Choose a Three Day Water Fast?

This year I’m attempting to do a 3-day water-only fast at the beginning of every month. This length of a fast is actually called a prolonged fast.

There are reasons for three days specifically. This length of a fast allows most people to get into a state of ketosis and induce autophagy. A 2010 study showed significant autophagy in mice after 24-48 hours. Since mice have a much faster metabolism, this could mean 48-96 hours in humans, but more studies are necessary. {* } Additionally, 3-day water fasting is a lot less daunting than facing a fast that is 5 or 7 days long.

At 3 days I’m also not risking any huge muscle or strength loss and the subsequent downregulation of metabolism. { *, * } At the time of writing this I have already done this specific fast 3 times and I can attest at least from an anecdotal perspective that there is no muscle loss. Oddly enough, exercising through the fast helps curtail hunger pangs. And strength training is a great way to further limit any muscle loss as it will keep signaling to your body to hold on to muscle mass as you force your body to use its own energy stores.

UPDATE: Due to the current COVID-19 pandemic, I am actually putting the extended fast plans on hold until further notice. The simple reason is that prolonged fasting actually raises your cortisol levels which can lead to a weakened immune system.

The truth is we simply do not know how a body in a fasted state would react to the virus. I think that practicing time-restricted feedings (aka intermittent fasting) is still okay, especially if it’s helping you stay away from mindless snacking or stress-eating.

More Fasting Resources:

• Intermittent Fasting for Beginners
• Different Types of Fasting Protocols
• Autophagy and Fasting: The Secret to Anti-Aging

XO, Marina

Disclaimer: I am not a medical doctor or Registered Dietitian. The information presented is not medical advice. It is purely to share my experiences and opinions based on the linked research. As always, check with a doctor before making any fitness or nutrition changes. The author and blog disclaim liability for any damage, mishap, or injury that may occur from engaging in any activities or ideas from this site.