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Keto Flu

Overcoming the addiction to sugars and carbohydrates

What is the keto flu?

Any major dietary or lifestyle change has the potential to cause discomfort or lets face it, even mess you up for a bit. This is sometimes referred to as a ‘flu’. It’s the most common time during which people will quit their dietary or lifestyle shift as many simply feel they are unable to function without significant carbohydrates and snacking throughout day.

[Taken from:]

"Here we’ll discuss the major downside to starting a ketogenic diet or a low carb one, and how to minimize the discomfort often accompanying this adaptation period."

Like most people you’ve probably spent 20 – 60 years feeding your body a significant amount of carbohydrates and much of them from poorly chosen overly processed sources.

Your cells, organs, central nervous system and brain have all adapted to it through hormonal and metabolic responses normally running in the background. Switching fuel sources, like eating less carbs and more fat, is likely to throw your body and brain for a loop.

To be clear, the “keto flu” label is a bit of a misnomer. It’s more akin to carbohydrate withdrawal symptoms resulting from a shifting hormonal states and imbalanced electrolyte adjustments that are along for the ride. Regardless, this buzz term is in the general consciousness now so we might as well keep using it for now.

Before diving into the details, keep in mind that the following four books should teach you nearly everything you need to know about low carb and ketogenic diets, including how to handle the keto flu. The rest of the relevant science is dispersed amongst hundreds if not thousands of papers only a search away on PubMed.


The trials and tribulations people encounter during the induction phase are unpredictable, but usually not too severe. They can range from nothing at all, to mild discomfort and mental fog, all the way through to full blown flu-like symptoms.

For example, the keto flu may involve nausea, fatigue, headaches, cramps, diarrhea etc. In severe cases, high blood pressure and arrhythmia can manifest.

It is wise to make an effort to reduce stress levels during this adaptation phase. Furthermore, exercise performance may suffer for a couple of days or weeks, but this is nothing to worry about. It’s a well-known phenomenon and is not indicative of long-term issues [1].

All it requires is acknowledging that exercise performance will probably suffer whilst the body adapts to using more fat and less carbs. See our post about high-intensity training and low carb diets for more.

It is worth noting that we have a diverse population of bacteria, viruses and other critters in our guts, so any major dietary or lifestyle change can likely disturb our gastrointestinal system and thus toilet habits in the short to medium-term.

The flora and fauna in our guts is commonly referred to as our gut microbiota and it is worth exploring in terms of dietary individualization another time. For now, understand that there’s nothing inherent about ketogenic diets per se that can cause issues such as gastrointestinal distress.

Odds are, it’s your unique and adorable snowflake metabolism taking its sweet time to adapt. Please know that in all-but rare metabolically deranged cases, everyone can adapt to a ketogenic diet or a low carb diet.

Unsurprisingly, there appears to be a reasonable correlation between the dieter’s previous lifestyle and severity of flu-like symptoms. If you’re a person already eating a higher fat and lower carb diet, the more likely you are to embark on a ketogenic diet or merely a low carb one with little fear of discomfort.

The induction phase of a diet typically lasts a few days to a couple weeks, at which stage the symptoms dissipate and energy levels return – usually with a vengeance!