The ketogenic or keto diet encourages the fat-burning metabolic process of ketosis; many people follow this eating plan to lose weight. With global adult obesity mortality nearing three million deaths every year, the demand is high for healthy eating habits. Though there are pros and cons to the keto diet, it has become increasingly popular in recent years. One temporary downside to this lifestyle is the keto flu, a common early side effect of the body adjusting to ketosis.

Keto Diet Side Effects

Most people who switch to the keto diet undergo a significant change to their former eating habits, notably the lack of carbohydrates. Sugar cravings are a major early side effect, especially for those who abruptly cease hearty helpings of bread and pasta, and yummy sweets like chocolate. Other side effects include mood swings, nutritional deficiency, frequent urination, excessive thirst, and persistent hunger. It may take some time for the body to get used to this new normal, but the effects usually subside around the second or third week of the diet.

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Keto Flu Symptoms

Many people report feeling sick as a result of their new keto diet. Often referred to as the keto flu, the symptoms are caused by the decrease in carbohydrate levels in the body, which must learn to burn fat instead. Symptoms can include nausea, vomiting, diarrhea, headache, and muscle pain. These symptoms can be discouraging to those trying to stick with the keto diet, but are generally short-lived.

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One major sign of keto flu is a persistent headache, often a throbbing in the temples and sharp pain in the head. This happens as the body adapts to having fewer carbs at its disposal. During the first few days of the keto diet, energy, insulin, and nutrient levels fluctuate. Giving the body time to relax, rest, and find balance is key to minimizing painful headaches during this time.

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Nausea and Vomiting

People experiencing keto flu may go through waves of nausea and vomiting. An upset stomach at the beginning of the diet is normal, as the body becomes more familiar with greater amounts of fat and protein. In the early stages of the diet, the body loses more sodium and water than usual, causing these symptoms. There are a few ways to keep these symptoms under control.

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Drink Lots of Water

Doctors recommend people with keto flu stay well-hydrated. While the goal of eight glasses is ideal, it’s especially important for those on the keto diet. That’s because a lack of carbs may require the body to go through water stores, making dehydration more likely. Good hydration can also ease other keto flu symptoms, such as tiredness and muscle pain.

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Boost Electrolytes

People struggling with keto flu may feel better if they replace some of the electrolytes lost as insulin levels change. The keto diet eliminates potassium-rich fruits and veggies, and getting enough nutrients is essential, regardless of one's eating plan. Leafy greens and avocados are keto-friendly and high-potassium alternatives that also deliver big doses of magnesium to soothe sore muscles and help with sleep.

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Minimize Strenuous Activity

While people on the keto diet often want to lose weight by curbing their carbs and working out at the same time, experts recommend avoiding intense physical activity until the keto flu passes. These symptoms are signs to rest and recover rather than run for miles. The body is adjusting to a new diet and source of fuel, and until symptoms cease, it’s best to take it easy on the physical activity. Light exercise like yoga or stretching may help with tension and release endorphins, but intensive running, weightlifting, and sports should wait.

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Prioritize Sleep

An adequate amount of sleep will also help shorten the duration of keto flu. Studies show low-carb intake from the keto diet can cause changes to sleep, particularly deep stage and REM sleep. Reduced hours of quality sleep can make people irritable, especially when they are dealing with other keto flu symptoms. Cut down on stimulants like caffeine, minimize technology in the bedroom, or relax in a bath before bed to properly prepare the body for sleep.

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Diet Adjustments

Cravings are a normal part of the keto diet, particularly for people used to eating all the pasta and cookies they want. Over time, the keto diet can reduce cravings for unhealthy foods and carbs, which makes it easier to stick to the diet. It can take weeks or months to reach that point, however, so some people find that a gradual progression into full keto — reducing carbs while boosting protein — makes the transition more palatable. This method may even reduce the severity of keto flu symptoms.

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Medical Advice

In some cases, the keto diet is an easy adjustment with few side effects. Others may go through multiple weeks with keto flu. The severity of symptoms varies from person to person, depending on metabolism, previous diet, and countless other factors. Hydration levels and carbohydrate withdrawal can also impact an experience with keto flu. After all, this high-fat diet contains just five percent carbohydrates, a big change from the norm for many people. If keto flu symptoms continue for weeks on end, and an individual feels very sick, they should speak to a doctor about their next steps.

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