Keto made easy

Is Keto Flu Real, or Is It Carb and Sugar Withdrawal?

2017-08-05

A rant just under three minutes long about a name. I didn't like "keto flu" then, and this video is the short version of why.

In this video

Watching this in 2026: the half that holds up

The strongest part of this video isn't the withdrawal theory. It's the unbundling. "Keto flu" gets used for three or four different problems, and each one has a different fix. Telling someone with cramps to "push through, it's withdrawal" is as unhelpful as handing electrolytes to someone who's just tired because they're two weeks in.

I said the same thing in the MyFitnessPal video: some people think electrolytes cure all keto flu, and some keto flu is just not being efficient at ketosis yet (video DoSUgIr2rNo).

The research on the name itself is thin. The one keto-flu paper on the evidence page is a content analysis of online posts: people's reported symptoms clustered in the first weeks and were mostly described as passing (Bostock 2020). That fits "it's temporary." It's posts, not a trial, so it can't tell you what causes it.

The claim worth unpacking: "it's withdrawal"

I called it opinion in the video, and it still is. None of the evidence pages has a study that tests sugar withdrawal as the cause of keto flu symptoms. So that stays my view, not a finding.

What the evidence page does describe is a mechanism for the electrolyte half. Insulin makes the kidneys hold on to sodium and potassium; in a 1975 study, raising insulin while holding glucose constant cut urinary sodium, potassium and phosphate excretion in healthy men (DeFronzo 1975). Cut carbs, insulin drops, and the reverse is the expected direction: more sodium goes out. The evidence page is clear that no highly cited trial directly measures this on a ketogenic diet in adults. It's physiology from fasting and insulin studies, not a keto trial.

So the two explanations aren't competing. My "withdrawal" idea is unproven. The "you're losing sodium" idea has a mechanism behind it, even without a keto-specific trial. Both can be true for the same person in the same bad week.

Then vs now: salt

In this video I said electrolytes come mostly and most safely from vegetables, and to see a doctor before supplementing (video 9r2Y74AnjUQ). That stayed. What moved was salt.

Later in 2017 I recommended light salt, the potassium-chloride kind (video lbRPlGZ3Rvw), and I did again in the 2018 basics video (video UygKGoP_BtA). In another 2018 video I said I used to recommend light salt and had moved to a pure potassium-chloride salt substitute ("No Salt"), because I was getting my sodium from bouillon (video -dHjt_Bpruk). Both 2018 videos carry the same upload date, so I can't tell you for sure which came first.

For reference, US intake guidance puts the adult sodium adequate intake at 1,500 mg/day and says to reduce intake if it's above 2,300 mg/day; for potassium it's 2,600 mg/day for women and 3,400 for men (NASEM 2019). WHO suggests potassium-containing salt substitutes in place of regular salt, except for people at risk of high potassium (WHO).

That exception is the whole reason I said "talk to your doctor" at the end. If you have kidney disease, or you take blood pressure medication, salt substitutes and potassium supplements are not a self-serve fix. Get the go-ahead first. More in sodium, potassium and magnesium and light salt.

Key points