The Keto diet is a popular way to lose weight by upping your dietary fat intake and cutting your carb consumption. But for some people that means experiencing fatigue and brain fog for a little while. Does this mean the Keto diet is unsafe or unhealthy? Turns out, this is a normal phase of the Keto diet and nothing to be afraid of. Here’s why.

When you’re on the Keto diet, your body moves into a state of ketosis. That means that instead of getting energy from sugar, you get it from both dietary fats and your body’s own fat stores. In order to get into ketosis however, you need to seriously reduce dietary carbs.

And that might seem contradictory to what we’ve been told about the brain.

Basically, the brain needs glucose (sugar) in order to function properly. And according to Harvard Medical School, “Because the brain is so rich in nerve cells, or neurons, it is the most energy-demanding organ, using one-half of all the sugar energy in the body.”

So, what happens to your brain when you drastically cut carbs (sugar) from your diet?

Well, it goes through a glucose withdrawal, and you might experience fatigue and brain fog during the first week or two of the Keto diet. However, the brain learns to adapt and can actually get up to 75 percent of it’s energy from ketones, or fat-derived energy sources.

It’s been found that people on a Keto diet actually experience an improvement in cognitive function, too. So, while the initial phase of the Keto diet might be difficult, you can expect to see improved cognition in the long run.

It’s important to note, however, that even if many people have success with the Keto diet, there’s no one-size-fits-all diet. If brain fog and fatigue persist, or you feel unwell, it’s okay to seek nutritional and dietary guidance to find a diet that’s best for you and you body’s needs.