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Understanding keto flu symptoms and treatment

Keto flu symptoms can occur within the first two days of starting the keto diet. Here's how to reduce them.

Tayla Holman
January 02, 2024
The keto diet can cause flu-like symptoms in response to carb withdrawal.

Starting a new diet is a common New Year's resolution, and one of the most popular among them is the keto diet. This low-carb, high-fat diet has been hailed for its weight loss potential. But some people may be surprised to find that they experience flu-like symptoms after starting the diet — often referred to as the "keto flu." While keto flu symptoms can be unpleasant, they're usually temporary, and you can take steps to reduce them.

If you're thinking of trying the keto diet this year, read on to learn more about the keto flu, including what to expect and how to minimize its effects.

What is the keto diet?

The ketogenic, or keto, diet is an eating pattern that focuses on low amounts of carbohydrates, high amounts of fat and low to moderate amounts of protein. This usually works out to 70% to 80% fat, 10% to 20% protein and 5% to 10% carbohydrates.

The idea behind the keto diet is that, by reducing carbohydrates (the body's main energy source), you can force your body to burn fat for fuel. Normally, your liver converts carbohydrates into glucose to fuel your body. But when there isn't enough glucose, the body starts breaking down stored fat. The liver then produces ketone bodies from fat, which can be used as a source of fuel in the absence of glucose. The accumulation of ketone bodies in the blood is called ketosis. It usually takes a couple of days to reach ketosis, and eating too much protein can stop that process.

What causes keto flu?

When your body enters ketosis, you might experience flu-like symptoms. This is your body adapting to carbohydrate withdrawal. The sudden switch from using carbs and glucose as fuel to using fat as fuel can be confusing for your body. Normally, your body only enters ketosis if you're starving or fasting. It can take some time to adjust to this new way of eating.

The symptoms of keto flu usually appear within the first two days of starting the diet. They can range from mild to severe. The symptoms usually last a few days, but they can last several weeks in some cases.

Signs of keto flu

Keto flu symptoms may include:

  • Brain fog
  • Cramping
  • Diarrhea or constipation
  • Dizziness
  • Food cravings
  • Increased thirst
  • Irritability
  • Nausea
  • Stomachache
  • Trouble falling or staying asleep

How can you reduce keto flu symptoms?

The symptoms of keto flu can be uncomfortable, but you can manage or reduce them in a few ways.

Transition gradually

If you plan to start a keto diet, slowly cut back on carbs while increasing the amount of fat and protein. This can help you ease into the diet and make the transition smoother. Eating more fat can also help reduce cravings for the foods you'll need to avoid on the diet, such as bread and pasta.

Stay hydrated

Drinking enough water is key for good health in general, but it can also help reduce keto flu symptoms. The diet can quickly deplete your water stores, putting you at risk for dehydration and electrolyte imbalances. Glycogen is the stored form of carbohydrates, and it binds to water in the body. When you reduce your carb intake, glycogen levels also go down. Additionally, ketones have a diuretic effect, so you may urinate more frequently when you switch to a keto diet. Staying hydrated helps replace lost fluids and minimizes symptoms like fatigue.

Adjust your workout routine

Exercise is important for staying healthy, but avoid strenuous exercise if you're experiencing keto flu symptoms. Focus on lighter activities such as walking or yoga instead.

Moderate caffeine intake

Caffeine is a stimulant, and it can have a negative impact on sleep. It's not uncommon for people who have keto flu to have trouble sleeping, so cut back on caffeine to help reduce this risk.

Making healthy choices year-round

If your symptoms don't improve after a couple of weeks or if you're experiencing symptoms such as fever or vomiting, talk to your doctor. Consult your doctor before starting the diet, too. While it's safe for most people, the keto diet may not be appropriate for children, teenagers or people who are pregnant or breastfeeding.

January 02, 2024