The Keto Flu: What You Need to Know Before Trying the Keto Diet

A pounding headache, an uneasy and unsettled stomach, dizziness – these are all common symptoms of the seasonal flu. But if you recently started the keto diet, they can also be unexpected side effects of what you’re eating.

The keto diet is all about low carb, high-fat foods and achieving ketosis. Once ketosis kicks in, your body starts producing ketones and burning fat for fuel. And that can lead to a whole bunch of benefits, from weight loss to reduced risk of health conditions like diabetes. Yet ketosis can come with some unexpected side effects, which are called the keto flu.

If you aren’t prepared to face the keto flu, it can make you feel terrible. Fortunately, there are simple ways first-time keto dieters can tackle this unusual flu head-on and combat its symptoms.

What is the keto flu?

The keto flu might feel like a virus, but it’s your body’s response to a drastic change in the kinds of foods you’re eating. Specifically, it’s an onset of symptoms that are caused by a dramatic shift in nutrients as you limit carbohydrates and increase your fat intake.

According to the latest Dietary Guidelines for Americans, a balanced diet is made up of about 45 to 65 percent carbs, 10 to 30 percent protein and 20 to 35 percent fat. However, when you switch to the keto diet, you’ll be eating macronutrients in a totally different, less rounded-out way. Because you’re reducing carbs, your body will need to adjust and adapt. That’s why ketosis begins.

As you significantly slash the amount of carbs you’re consuming, your body starts producing ketone bodies. Made from fat, the ketone bodies become your body’s source of energy. And because your body isn’t used to using those ketones, you start to experience physical side effects of this change.

That’s where the keto flu appears. You’ll feel unwell and see physical symptoms manifest as your body works to change up its usual processes and use a new kind of fuel. You can think of the keto flu as a kind of shock to your body, or even a series of withdrawal symptoms as you take away its familiar fuel.

Fortunately, keto flu is merely an adjustment period. It’s short-lived and temporary, and symptoms usually disappear within weeks.

Keto flu can bring on aches, nausea and more

The seasonal flu and keto flu have a lot in common when it comes to their symptoms. When you restrict your carbohydrate intake, you’ll feel like you’ve been hit by one tough bug. 

And signs of the keto flu can start appearing within a day or two of starting the keto diet. It varies from person to person, but symptoms can come on slowly or quickly. They also range from mild to severe.

Typical symptoms of the keto flu are the same symptoms of any low- or limited-carb diet. They include nausea and vomiting, stomach pain, muscle soreness or aches, dizziness, headaches and general weakness. Mental symptoms can happen too, like irritable moods, inability to concentrate and difficulty sleeping. You might even find yourself having unusual sugar cravings.

Whether you’re experiencing a few standout symptoms or wind up getting hit with every one of them, the keto flu can make for a rough introduction to your new diet.

How to limit keto flu symptoms

There is some good news about the keto flu: it isn’t guaranteed to happen. Some people never experience it, while others might have a few minor symptoms like headaches here and there.

So, if you’re hoping to avoid this food-related flu altogether, it’s totally possible. If you understand what tends to cause keto flu symptoms, you can ease yourself into the keto diet and help your body make a smoother transition into ketosis.

Here are a few tips you’ll want to keep in mind as you work to avoid the keto flu.

Drink plenty of water

It’s always important to stay hydrated, but it’s especially critical when you’re starting the keto diet. This unique approach to eating can cause your body to shed its stash of water faster than usual, as carbohydrates are key to binding water. So, when you slash your carb intake, you can unexpectedly become dehydrated. 

Making sure you’re drinking plenty of water can combat common keto flu side effects like muscle cramping and fatigue. Choose water over other beverages, and keep track of how much you’re drinking throughout the day to keep a close eye on your hydration level.

Reach for extra electrolytes

As you change up the foods you’re eating, you might unexpectedly create nutritional deficiencies. And one key nutrient that can suddenly fall by the wayside as you start the keto diet is electrolytes. 

When you dive into the keto diet, it’s easy to cut out fruits, vegetables and beans. However, these foods contain potassium, a critical mineral. Your body will also release a whole bunch of sodium as your insulin levels decrease (a common side effect of going keto). This can create a lack of electrolytes, which can then potentially cause or exacerbate some of your worst flu-like symptoms.

Combat this by ensuring you’re getting both salt and potassium. Seek out potassium-rich foods that are keto-approved, like leafy greens or avocados. Other electrolyte-filled foods that contain magnesium and calcium can also help you balance your mix of minerals.

Cut back on carbs gradually, not immediately

It’s so easy to dive right into the keto diet and prioritize fat over carbs in your very first keto-friendly meals. However, jumping in rather than easing into these new habits can also lead to unpleasant keto flu symptoms.

The keto flu is typically brought on because keto essentially shocks your body by taking away its usual fuel source. To avoid this, make the transition from your current eating habits into the keto approach a slow one. Ease your body into the change by slowly cutting back on carbs. You can gradually reduce your intake day by day until you’ve fully adopted keto habits.

With the right approach, you might be able to avoid the keto flu completely

Switching to the keto diet doesn’t have to leave you feeling absolutely awful. Now that you understand how surprising a low carb, high fat diet can be for your body, you have the knowledge you need to avoid the keto flu completely.

While some unpleasant side effects or symptoms can still appear as your body adapts to relying on fat instead of carbs for fuel, you may be able to minimize your flu-like experience. Just make sure your body is getting all of the important nutrients it needs, from water to electrolytes to your usual vitamins and minerals. And, if you’re leaving a carb-heavy diet behind, you’ll want to make slower shifts in your eating habits to ease the internal transition.

As you transition to the keto diet, make sure you’re covering all of your nutritional bases with more information:

• A Better Way to Keto
• 4 Supplements You Need on a Keto Diet
• Dirty vs Clean Keto