Remedy for Symptoms of the Keto Flu

Keto Flu Explained: Why Low-Carb Diets Can Make You Feel Sick and Tired

The ketogenic diet is a popular weight-loss search online with celebs also touting its supposed benefits. But the high-fat, low-carbohydrate eating plan is not without its drawbacks.

Experts warn that the diet is extremely restrictive and not sustainable. They also say it can lead to nutritional deficiencies, high cholesterol, or a serious condition called ketoacidosis. But even before long-term problems set in, many people who try the diet report other unpleasant side effects, otherwise named: keto flu.

Keto flu is an unofficial way to describe how some people feel shortly after starting a ketogenic diet. It can include both physical and emotional symptoms—like nausea, cramping, lack of energy, and irritability, to name a few. It's what happens when the body and the brain are forced to adjust to a sudden carbohydrate deficiency, said Abbey Sharp, RD, a Toronto-based nutritionist and blogger at Abbey's Kitchen.

Proponents of the keto diet say that these flu-like symptoms are only temporary and that certain remedies can help reduce or eliminate them altogether. But is it really worth subjecting yourself to, even if just for a short time? Here's what our experts said.

Keto Flu Symptoms

There's no scientific definition of keto flu, but it's often described as flu-like symptoms that start soon after a person cuts carbohydrates largely out of their diet—to enable "ketosis," a sort of starvation mode in which the body burns fat rather than glucose, the ketogenic diet allows for only 2-5% of a person's daily calories to come from carbohydrates.

"Very often, people don't feel well when they're on the ketogenic diet, and it tends to be worse in the early period," stated Edward Weiss, Ph.D., associate professor of nutrition and dietetics at Saint Louis University. "This is something largely anecdotal—we don't have studies on this—but it's probably very real." At the start of this diet, people can experience:

  • A sudden drop in carbs which can lead to a decline in energy levels, with some people reporting unusual fatigue, confusion, or brain fog. "The symptoms are from your brain needing to adjust to the new source of energy, while also trying to deal with a drop in electrolyte levels as you lose weight," stated Sharp. It can also cause nausea, stomach pain, cramping, and constipation as well, due to the diet's high-fat and low-fiber makeup.
  • Bad breath or foul-smelling sweat and urine. Ketones, a type of acid, are byproducts of fat breaking down in the body. "The smelly factor comes from the fact that acetone, a byproduct of ketone metabolism, seeps out of your body," said Sharp.
  • Irritability and mood changes which Cynthia Sass, MPH, RD, Health's contributing nutrition editor, stated that many clients who have tried the ketogenic diet have also reported. While people don't necessarily feel hungry on the keto diet—thanks to its high allowance for fat and moderate amounts of protein—some do report serious sugar cravings.
  • Changes in athletic performance because adopting a ketogenic diet may also hamper athletic performance, indicated Weiss, even though many athletes try it thinking it will have the opposite effect. In a recent study, Weiss and colleagues found that after four days on a keto diet, participants performed worse on anaerobic exercise tasks—which involve short bursts of intense activity—than those who'd recently gone on a high-carb diet. "Our participants were right in that period of feeling terrible," stated Weiss. "They were tired, hungry, lethargic." But the researchers suspected that there's a biological reason they performed worse, as well: They had higher levels of acid in their blood, a result of their bodies burning ketones.

RELATED: 6 Really Good Things That Happen to Your Body When You Quit Sugar

How Long Does the Keto Flu Last?

"Most people find that [they] feel better in a few days, or up to a week, once [their] body adjusts," Sharp stated, and also added, "[w]hether or not you want to put your body through that is a personal choice."

As for athletic performance, the participants in Weiss' study weren't followed long enough to see if performance improved after more than four days on a ketogenic diet. But other research suggested that acid levels in the body tend to normalize after a few weeks, while performance remains compromised.

Keto Flu Remedies

The keto diet was originally used as a treatment for epilepsy, and scientists are also looking into its potential benefits for people with diabetes or insulin resistance. "I don't really recommend the keto diet in anything other than clinical disease management settings, because it is incredibly restrictive," stated Sharp.

Some recommendations to manage keto flu includes staying hydrated, getting plenty of sleep, and finding ways to manage stress—to reduce the unpleasant effects of the ketogenic diet on your body. Other recommendations include electrolytes, ketone supplements, or bone broth—high in sodium and other minerals—to replace some of what the body is missing in the early stage of the diet.

Certainly, prioritizing sleep, hydration, and overall healthy habits can keep you from feeling even worse, whether you're on the keto diet or not. But the experts we spoke with agreed that avoiding ketosis altogether is a smarter way to feel good while you're trying to lose weight, rather than putting a Band-Aid on something that could have more serious consequences down the road.

Research on low-carb diets has also shown that while people do tend to lose weight faster in the beginning, there is no long-term difference when compared with other diets of equal caloric intake. "In other words, if you enjoy carbs, a balanced diet that includes them can lead to just as much weight loss," Sharp added.

RELATED: 6 'Bad' Carbs That Are Actually Good For You

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How to Avoid Keto Flu

It is possible to cut back on sugar and carbs—and, yes, lose weight—without experiencing these nasty symptoms, stated Sharp, adding, "while you cannot achieve ketosis without a significantly reduced-carb diet, you can absolutely reap a lot of the potential glycemic benefits of a low-carb diet—without some of the downfalls, like keto flu—simply by choosing the right carbs."

The key is making sure the carbs you do keep in your diet are rich in fiber, like whole grains, vegetables, and fruits. When you do eat those carbs, Sharp added, pair them with some fat or protein; this slows their glycemic impact, even more, preventing the blood-sugar spikes, and subsequent crashes, that lead to cravings and crappy feelings.

Sass recalled reading about someone who became irritable and had trouble sleeping after adopting an ultra-low-carb diet, and stated, "[t]hose side effects subsided after...fruit, whole grains, and starchy vegetables [were added back] to [the] diet."

A Quick Review

Keto flu is the unpleasant flu-like side effect of the popular, ketogenic diet. The drastic dietary changes—high fat and low carbs—of this weight-loss plan results in physical and emotional symptoms which can affect your body for up to a week as it adjusts at the start of this diet. Specifically, dieters may experience reduced energy levels due to the drastic decrease in carbs, bad breath, irritability and mood changes, and changes in athletic performance. Nutritionists warned that long-term, this weight-loss plan can lead to nutritional deficiencies, high cholesterol, or more seriously, ketoacidosis.

To remedy the side effects of keto flu, nutritionists recommended staying hydrated, drinking electrolytes, ketone supplements, or bone broth, getting plenty of sleep, and adopting healthy habits and finding ways to manage stress. However, to not drastically starve your body and reduce weight without these symptoms, reduce sugar and carbs, and make sure the carbs that remain in your diet are rich in fiber.

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  1. Wroble KA, Trott MN, Schweitzer GG, Rahman RS, Kelly PV, Weiss EP. Low-carbohydrate, ketogenic diet impairs anaerobic exercise performance in exercise-trained women and men: a randomized-sequence crossover trial. J Sports Med Phys Fitness. 2019;59(4). doi:10.23736/S0022-4707.18.08318-4

  2. Carr A, Sharma A, Ross M, Welvaert M, Slater G, Burke L. Chronic ketogenic low carbohydrate high fat diet has minimal effects on acid–base status in elite athletes. Nutrients. 2018;10(2):236. doi:10.3390/nu10020236

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