The ketogenic diet has a sickening side effect that some dieters experience: the keto flu. Here's what to do if you have it.

By Ananda Eidelstein
February 06, 2018

The ketogenic diet (known as the “keto diet)” is popular, but there's a sickening side effect you may not have heard about: the keto flu, which is caused by the body adjusting to the diet's high-fat, moderate protein, and low-carbohydrate regimen.

As your body adapts to the diet's strict restriction of carbs, uncomfortable flu-like symptoms can creep in, says Lisa Young, New York University Professor of Nutrition. The dizziness and shakiness that some people experience with the keto flu (also known as the carb flu) might start a day or two after you begin the diet.

“You might also have sugar cravings, poor concentration, irritability, and brain fog,” she adds.

The idea of the diet is that by limiting carb intake, your body lacks what it takes from carbs to use for energy, so it makes the switch to burn fat as its fuel source. Though not everyone who tries the keto diet gets the keto flu, the symptoms can occur because instead of burning sugar for energy, the body is burning fat, says Young.

To alleviate keto flu symptoms, have a little fruit (an apple will not ruin your weight loss, says Young). Sprinkling a bit of salt in your water, since you’re losing so much sodium and potassium, may also help. Avocado and leafy greens such as spinach, both allowed in the keto diet, can replenish some of the potassium you're losing, too.

The takeaway: The keto diet has been around for a while. Since it's been used, successfully, to treat children with epilepsy and some brain injuries, Young recommends that only those with those conditions try it.

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We broke down the keto diet in a very detailed guide, here.