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Operation Flight – My first hand experience of the dreaded ‘Keto Flu’

My last post was about beginning a journey of weight loss in order to achieve some of my martial arts goals more easily, specifically jumping high so I can kick people in the head – or at least above the belt. I’ve called this plan ‘Operation Flight.’

In my wisdom, I decided that switching to low carb would be the best way to achieve this. When I say switching to low carb, I specifically meaning, following the macros commonly used by people on the ‘Keto Diet.’

Eating ‘keto’ typically means getting most of your calories from fat, around 65-70%. Getting around 10% of calories from carbohydrates and the remainder from protein. Now I’m not an expert so I’m not saying this is exactly correct, it’s just how I understand it.

So around 11 days ago I started ‘eating keto’. These are the things I thought might happen:

  • I might crave carbs for a few days
  • I would lose quite a bit of water weight (good for jumping)
  • I might suffer from the keto flu (whatever that is)

Well, having now ‘crossed over’ to where my body is now apparently using fat for fuel instead of carbs I can give a detailed account of my experience, including the horrible (and boy is it horrible) keto flu.

Day 1: This is easy…

Day 2: Wooh, still easy – weights work out in the morning, Taekwondo training at night. All good. Can feel the glycogen draining from my muscles.

Day 3: I actually wrote in my diary – “I can’t believe I feel this good.” Interval cardio on the rowing machine. No problem

Days 4-6: Keto Flu. These days were a hard out slog. Getting up was hard. One day I just lay on the couch instead of working out. Walking was hard, climbing stairs was hard. I constantly felt out of energy and slightly nauseous. And then there was the taste in my mouth…ew.

Frankly, the keto flu symptoms were ghastly. If you want to know more about the symptoms of the keto flu you can read about them here on this Healthline post. I didn’t have them all, but the ones I did have were severe and were enough that I almost forgot why I was doing this in the first place. I didn’t quit but it came close. Luckily, quitting sugar last year has gotten me out of the habit of reaching for the carbs so I made it through.

I Facebooked my hard out online workout buddies. They told me it would take a week. I then Googled the keto flu some more and found it actually takes around two weeks to reach peak performance again.

The night of day six was the worst. I woke up in the night feeling nauseous and the following day wasn’t much better.

Day 8: I woke up. I felt OK. I thought, ‘Am I over it?’

Day 9: Sigh, I’m not over it. This workout is still way too hard. But hey, I’m not hungry!…at all.

Day 11: Got up this morning, did my usual workout and even upped my weights. I am officially over the keto flu. Give me a couple more days and I will be cranking.

The key learning from this for me was: Don’t underestimate the transition to ketosis. I was not able to maintain my workout routine which did feel a little counterproductive at the time. However, now I am through the worst I feel like my normal self. The other bonus is that I need less overall calories to feel full than I did when eating a diet higher in carbs. This will make the weight loss process faster and more sustainable.

But have I lost weight? Has this been the right choice for Operation Flight?

I have lost weight. Last weeks tight pants are now this week’s comfortable pants and hopefully future loose pants.

The only problem now is what do I do about Christmas? Now that I know it’s a full on, hard out, gross two week journey to ketosis dare I reverse it with Christmas Cake?

My original plan was to ‘go keto’ until just before Christmas, eat sensibly of holiday treats and then go back to keto in the New Year to blast the last few pounds. But now? Knowing what I know about the process of getting into ketosis. I’m not sure I’m brave enough to leave and come back….

Would you be?


  1. Hi,
    Just read your blog post. I’m glad you were able to meet your goals and happy that was able to help (even if it was just for info about the length of keto flu). Hope the keto diet is continuing to serve you well. It’s still one of my favorites!


    • Thanks Jermaine. That’s cool that you noticed me commenting on your awesome content. I had some ongoing issues with maintaining my electrolyte levels at around 3 months so I’ve had to take a break for a while but I really loved living the keto lifestyle and hope to go back to it soon – hopefully minus the keto flu!


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