Is Fasting Good When You're Sick?

There’s an old adage I know you’ve repeated before.

If you’re sick with a cold you’re supposed to “starve the cold,” and if you’re sick with a fever you’re supposed to “feed a fever.”

This adage has some truth to it, but it’s probably not what you think.

If you ever find yourself with any kind of ailment, fever, cold, flu, etc, I think it’s important you know what studies show about eating versus fasting and how they can affect your health.

Studies Show Fasting Helps You Get Better Faster But You Should Fast When You’d Least Expect

If you get sick chances are one of the first things that’s going to happen to you is your normally consistent appetite will dry up like a drop of water on a hot windshield.

Depending on how sick you are it may be almost impossible to eat. And if you do eat, there’s a chance you might end up puking your guts out.

It turns out there may be an important biological explanation for this. An explanation you probably shouldn’t ignore.

In a recent study from Yale University (an animal study) a team of researchers tested what happened to mice who were infected with bacterial and viral infections that caused the exact same kind of inflammatory response to happen in their bodies.

Ruslan Medzhitov who was the team lead on the study told Yale News when animals are infected with various kinds of pathogens their first response is to stop eating and they switch to a fasting metabolic mode.

The reason animals stop eating is because a viral or bacterial infection leads to the formation of inflammatory molecules whose sole purpose is to regulate how the infection acts in the body.  

Even though you may think inflammation is bad, biologically speaking inflammation is essential for good health. Without the release of inflammatory molecules you’d have no way of fighting an infection as inflammation mobilizes a wide array of antibodies whose job is to kill off bacteria and viruses.

To see how important fasting was during the initial stages of infection the team split up two mice groups (bacterially infected and virally infected mice) into 2 smaller groups.

One group was programmed to receive sugar water and the other was programmed to enter a fasting metabolic state.

While both of the infections caused the animals to lose their appetites, the mice that received sugar water and were infected virally recovered faster than the bacterially infected.

The researchers theorized glucose may have helped protect the brains of the mice and other systems from inflammation.

Conversely, the bacterially infected who received sugar water died because the sugar (glucose) was observed to contribute to the formation of brain damage, causing them to have seizures and eventual death.

Medzhitov and his team believe fasting triggers the liver to produce ketones - which are the molecules formed when you’re in ketosis (often a byproduct of fasting).

The team believes bacterial infections may lead to the release of a tremendous number of free radicals during infection which could damage the brain and prevent it from absorbing glucose (which may lead to seizures).

On the other hand, since viral infections aren’t known to cause the release of free radicals the mice that were infected with viruses recovered faster since the intake of food calories helped to strengthen the immune system.

     So What about Humans?

               Should They Fast Too?

While the study I just described to you was only for mice, the question has to be asked if fasting is helpful for humans. Regardless of whether or not you’re infected with a virus or a bacterial infection.

Before I dive into this, let me just begin this by saying most colds and flu start as viral infections. Once your immune system is compromised the chances of succumbing to a secondary bacterial infection rise and then it’s hard to tell what exactly might be going on in your body.

And let me end cap that with this statement.

In the past few years intermittent fasting has been shown to help boost immune function across the board.

One of the ways it does this is through inducing autophagy which is the process by which your body breaks down unhealthy cells and assimilates the healthy parts of the cells back into the body to renew the immune system and promote better health.

You can learn more about autophagy in this article here.

And as Dr. Jockers writes:

“The practice of fasting allows the body to put more energy and focus into the process of effective immune regulation.  Fasting while drinking water and cleansing beverages flushes out the digestive system and reduces the number of natural microorganisms in the gut.  The microorganism count is typically regulated by the immune system.  So this allows the immune system to divert energy to other more important areas.

Intermittent fasting is a terrific regulator of the immune system as it controls the amount of inflammatory cytokines that are released in the body.  

Two major cytokines Interleukin-6 and Tumor Necrosis Factor Alpha promote an inflammatory response in the body.  Studies have shown that fasting reduces the release of these inflammatory mediators.  The immune system modulation that intermittent fasting provides may also be helpful if you have moderate to severe allergies.”

So based on that bit of information you may conclude that fasting is beneficial when you’re sick.

Yes and no.

Fasting before you ever get sick is certainly going to help you prevent illness, as intermittent fasting keeps you healthy and boosts immune function so you can fight off sicknesses of varying kinds.

But, if you fast and rest and get plenty of fluids (these 3 things must be done together for fasting to help) in the first few days of any infection it could help you get better faster.

Here’s why.

If you fast, rest, and get plenty of fluids you don’t waste energy finding/preparing/digesting food which allows your body to focus solely on fighting off the infection.

In addition, fasting deprives viruses or bacteria of nutrients they need to keep growing as well as encourages your body to remove infected cells through a process known as cell apoptosis.

And lastly, if you go back to the research study on the mice from above, when you fast your body will begin to move into ketosis. One of the primary ketones related to fasting is called beta-hydroxybutyrate (BHB). BHB has been shown to help normalize immune function.

Additionally, when your body is fueled by mostly ketones it helps to reduce inflammation. While you need inflammation to fight off infection, too much inflammation isn’t ideal for recovery.

Dr. Bill Rawls MD said this about what happens here.

“Some of the most promising recent science has come out of the Longevity Institute at the University of Southern California Leonard Davis School of Gerontology. In 2014, researchers there found that a three-day fast involving less than 200 calories per day could help revitalize the immune system on a cellular level.

Reporting their findings in the journal Cell Stem Cell, the study authors observed that when cells went without standard fuel from regular meals, the body switched to survival mode and ended up killing off old, damaged white blood cells [that are present when inflammation takes place] to conserve energy.”

   Here’s the Verdict On Fasting And Sickness

Please understand what I’m going to say doesn’t constitute medical advice for you.

All I’m presenting to you are my conclusions on intermittent fasting. If you are temporarily or chronically ill my suggestion is to get advice from your medical provider about intermittent fasting and illness.

For me personally, I think it’s OK to fast at the beginning of an illness. If you plan to intermittent fast it’s important to eat a ketogenic diet in order to get the body into ketosis and maintain ketosis.

Above all, be sure to get plenty of fluids as your body will need fluids to flush out toxic waste built up from the illness.

However, if you have an appetite while you’re sick and feel like you need food to help fight your sickness then I don’t think you should ignore those signals.

You should listen to your body in instances like this.

Fasting could help you recover quicker, it can also help you stay well, but it is not a silver bullet for wellness.