What is the ‘Keto Flu’?

What is the ‘Keto Flu’?

The trendy ketogenic diet, or ‘keto diet’, is the latest big thing in weight loss, lauded by celebrities like Jenna Jameson and Halle Berry.

The diet involves cutting out a ton of carbs – to 50 grams a day or less – to achieve a state of ketosis, in which the body burns fat for energy.

Despite its popularity, the keto diet is controversial. Some health experts say stay away entirely, citing unpleasant side effects, health risks, and the diet’s unsustainable nature. Keto followers even admit that if the diet isn’t done the right way, it can be the opposite of healthy.

One such side effect is the notorious ‘keto flu’.


“Some people report that when they start ketosis, they just feel sick,” says Kristen Kizer, RD, a nutritionist at Houston Methodist Medical Center. “There can sometimes be vomit, gastrointestinal distress, a lot of fatigue, and lethargy.”

The so-called keto flu usually passes after a few days, she adds.

Josh Axe, a doctor of natural medicine and clinical nutritionist, estimates that about 25% of people who try a ketogenic diet will suffer from this flu, feeling heavy fatigue.

Related: The Ketogenic Diet: What is it?

“That happens because your body runs out of sugar to burn for energy, and it has to start using fat,” he says. “That transition alone is enough to make your body feel tired for a few days.”

If you’re starting the keto diet and want to minimize the effects of the keto flu, drink plenty of water and get plenty of sleep. Natural energy sources like match green tea and organic coffee can combat fatigue, too.

Photo Credit: Yulia Furman/Shutterstock.com; Rimma Bondarenko/Shutterstock.com

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