How To Dodge The “Keto Flu”

We have written before about the ketogenic diet, in one of our mythbusting editions:

Ketogenic Diet: Burning Fat Or Burning Out?

The answer to the titular question there, by the way, is both: keto is good for short-term weight loss, but long-term adherence can bring health risks that may make it not worthwhile.

To this end, we could flippantly say that the best way to dodge the “keto flu” (the unwanted symptoms commonly associated with the transition to a ketogenic diet) is to not do keto, but the fact is that there are valid reasons why some people will want to do keto, e.g:

• to do it short-term, enjoy the weight loss, and then keep the weight off with a more rounded diet (such as the Mediterranean diet)
• to do it long-term, in order to manage refractory epilepsy symptoms (the only reason the ketogenic diet was first created and popularized)
• to do it long-term, despite the health risks associated with such (because we’re not the boss of you, and you get to decide for yourself which risks are worth it and which aren’t)

So, with that in mind…

What is the “keto flu”?

The “keto flu” is not in fact a flu of any kind (“flu” gets bandied around a lot in general parlance, but really the term should only be used to refer to variants of the influenza virus), nor indeed even an infection of any kind.

Instead, it’s a collection of symptoms that typically appear a few days into starting the ketogenic diet, and usually continue for a few weeks to a month or so.

The most commonly-reported symptoms are fatigue, brain fog, headache, mood changes, lightheadedness, bad breath, muscle cramps, reduced exercise capacity, constipation, and/or diarrhea.

About those latter two, you may be wondering “how can you have both constipation and diarrhea?” and the answer is that often people will get one of them and try to treat it, and now find they have the other and so they try to treat that, and so oscillate between the two for a bit. Which we cannot imagine is fun, but it’s a pattern that does play out a lot.

A big reason for this is that any sudden change in diet will cause a commensurately sudden change in gut microbiota, which will have many effects on the rest of a person’s health.

There are other reasons too, though, including hypoglycemia (very common when suddenly drastically cutting carbs, for obvious reasons of: fewer carbs in means less sugar in the blood) and electrolyte loss.

In a recent large review of studies found that symptoms like halitosis, constipation, nausea, and vomiting were the most frequently reported; children experienced more issues like hypoglycemia and vomiting, while adults reported dizziness and fatigue. Kidney stones were rare in short-term studies but occurred in an average of 14% of long-term ketogenic diet adherents:

Symptoms during initiation of a ketogenic diet: a scoping review of occurrence rates, mechanisms and relief strategies

How to avoid it (aside from “don’t do keto”)

There are several main things to consider:

• a more gradual shift into a ketogenic diet, rather than doing it overnight, will allow the gut microbiota to change more gradually, which will avoid many of the symptoms associated with gastrointestinal upset
• electrolyte replacement (sodium, potassium) and again, doing a slower transition, can help avoid the symptoms associated with electrolyte loss
• medium-chain triglyceride (MCT) supplementation helps maintain ketone levels and may ease symptoms (though may cause—rather than alleviate—gastrointestinal problems if not introduced gradually)

About those electrolytes:

Are Electrolyte Supplements Worth It? Here’s When To Take Electrolytes (And When We Shouldn’t!)

And about those MCTs:

How Beneficial Is MCT Oil, Really?

Not sure if keto’s for you?

Check out:

Which Diet? Top Diets Ranked By Experts ← this is great for comparisons of the various dietary approaches

Or if you prefer to do things your own way, then consider:

What Macronutrient Balance Is Right For You? ← this one’s really quite comprehensive, if you’d like to figure out your own best approach in a personalized fashion.

Enjoy!