What is The Keto Flu (and what to do about it)

Updated: Nov 30, 2020

What is the “Keto Flu”

The Keto flu is a term that has been dubbed to describe the unpleasant symptoms that many people can experience when they adopt a low carbohydrate/ketogenic diet. It’s not really a flu, and it’s not contagious, but it can definitely be very unpleasant. These symptoms can show up between 1-2 weeks after starting a ketogenic diet and most commonly between days 3-5. The keto flu is a product of change. The body is a very complex machine and cutting out carbohydrates turns a lot of dials leading to many compensatory effects, most of which we want, but the adjustment can be a little rough if not understood and taken into consideration. One of the main points I like to focus on here is that the keto flu is not a rite of passage and there are steps you can take to help prevent most of the symptoms and ease your way in your transition to becoming fat-adapted (using fat as the main source of fuel for your body rather than sugar/carbs) if this is your goal.

The main intervention on a ketogenic diet is to restrict carbohydrate to the point that the body has to switch from using glucose (sugar) for fuel to using fat (either the fat we consume or our stored body fat) for energy. Restricting carbohydrate to this degree keeps blood sugar and insulin levels low, which is what we want, however as discussed in the last blog post on sodium, low insulin levels and rising ketone levels cause sodium loss in the urine. This sodium loss leads to fluid loss (think: water follows sodium) which leads to many of the symptoms of keto flu including dizziness, feeling faint, fatigue, constipation and headaches. Further, the loss of sodium and fluid then goes on to trigger a stress response that increases adrenal hormones to reabsorb sodium to restore sodium balance, but unfortunately that action increases the loss of potassium. The loss of potassium then leads to other symptoms associated with keto flu such as muscle twitches and cramps, irregular heartbeats and muscle weakness. It’s like a bad domino effect.

In addition to the loss of sodium and fluid being the main driver of the symptoms of the keto flu, there is also an adjustment period as the body is transitioning from sugar burning to fat burning. Depending on how rusty your ketone producing gears are (meaning how metabolically flexible you are), there can be a bit of a lull in how quickly your body can get ketone levels up to par with your energy demands. This may lead to sugar cravings as the body is looking for its usual source of fuel and if not found, could lead to fatigue and lethargy until ketone levels are able to come up. The transition is different for everyone so it’s important to arm yourself with the knowledge to better understand what is happening and adjust as needed.

Lastly, the literature supports the notion that sugar is addictive and people who are “addicted” not only demonstrate similar addictive behaviors to substance abusers, but also can show similar neurochemical alterations in their brains, especially by affecting dopamine.

What are the symptoms of keto flu

Most of these symptoms were mentioned above, however as a quick list, the most common keto flu symptoms are:

  • Headache

  • Constipation

  • Muscle cramps

  • Weakness

  • Fatigue

  • Lethargy

  • Irritability

  • Insomnia

  • Difficulty focusing (“brain fog”)

  • Dizziness

  • Sugar cravings

How to prevent (or treat) the keto flu

Sodium and Hydration:

The main way to prevent or treat the symptoms of keto flu is to go to the beginning of the domino cascade described above and replace sodium. Since water follows sodium, replacing lost salt and fluid can help reduce your symptoms significantly and often eliminate them altogether. I usually recommend that people drink 1- 2 cups of a salted broth daily, especially during the first few weeks of starting a keto lifestyle to prevent the symptoms in the first place, but if you do experience some symptoms, you could drink a glass of water with half a teaspoon of salt stirred into it. If the symptoms are related to sodium and fluid loss, you will usually feel better within 15 to 30 minutes. Some people like to opt for electrolyte replacement drinks, however if you do, make sure there is adequate sodium in them and no carbohydrates/sugar. A couple of brands I like (no affiliation) is LMNT and Redmond Re-Lyte. These are convenient (and tastier than adding salt to water) but not necessary. Staying hydrated is very important as well, but doesn’t negate the need for sodium replacement. We need both. Overhydration with plain water will dilute blood sodium levels and exacerbate low sodium symptoms.

MCT Oil:

Some people recommend adding MCT (medium chain triglyceride) oil in the first couple of weeks of a keto diet to aid the body in making ketones. MCTs are unique fats in that they travel straight to the liver to be converted to ketones and can even do this in the presence of carbohydrates. While a bit theoretical, increasing ketone levels right away might help your body adapt faster to this change in fuel source, especially if the fat burning gears are a bit rusty as we mentioned earlier. Of note, MCTs can cause loose stools if too much is taken too soon. Powdered versions of MCT oil seem to be better tolerated than the liquid form, but still should be increased gradually to avoid gastric distress. The other thing to consider is if you are embarking on a ketogenic diet for weight loss, adding MCTs initially to aid in your transition can be helpful, but after that, you want your body burning your own body fat over consuming extra fat.

Increase Dopamine:

If carb withdrawal is the culprit behind a person’s keto flu symptoms, it is encouraging and very helpful to focus on the fact that the symptoms are temporary and I usually recommend being intentional about doing other things that can naturally boost dopamine to curb out the effects such as:

· Eating foods high in the amino acid tyrosine (i.e. almonds, avocados, eggs, fish and chicken)

· Exercising

· Meditating

· Getting enough sleep

· Listening to calming music

· Working on something altruistic

Eat Your Veggies:

Anyone who knows me knows I am a BIG fan of veggies! Non-starchy veggies and low sugar fruits add volume, texture, fiber and essential vitamins and minerals (like potassium and magnesium) to your diet. They are a key component to a well formulated ketogenic or low carbohydrate diet with a few caveats that are beyond the scope of this post.

I hope this helps! Have you experienced symptoms of “keto flu” while following a low carb or ketogenic diet? Comment below!


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