Can Intermittent Fasting Cause Brain Fog?

Written by Andrew Brewer. ⚕️Reviewed and fact checked by our medical team.

Can Intermittent Fasting Cause Brain Fog?There are a lot of benefits to intermittent fasting, including weight loss, improved health, and reduced risk of many diseases. However, it’s not always easy to do – at least a first. Along with the good, there are also some negative side effects associated with intermittent fasting like hunger, lethargy, and in some cases, brain fog.

As people start to identify why they’re feeling the way they are, many start to wonder if intermittent fasting is to blame. Can it cause brain fog? Yes, but it won’t last forever. Here’s all you need to know to kick that brain fog to the curb.

Key Takeaways

  • Intermittent fasting can cause brain fog, which is characterized by feelings of confusion, forgetfulness, and slower cognitive processing. However, it is a temporary condition that typically resolves once the fasting window is over.
  • Brain fog is not inherently dangerous but can be uncomfortable and may affect daily tasks. It is important to be aware of the symptoms and take necessary precautions to minimize its impact.
  • Adequate sleep is crucial to prevent brain fog during intermittent fasting. Getting enough rest helps reduce confusion and disorientation.
  • Consuming high-value, nutritious foods that are rich in fiber and protein during eating windows can help manage brain fog. Such foods keep you feeling fuller for longer and promote mental clarity.
  • Taking breaks and engaging in lighter tasks during fasting windows can alleviate brain fog. Activities like going for a walk or switching to less demanding tasks can help reduce confusion and improve cognitive function.

What is Brain Fog?

Have you ever felt that haze in your mind? You’re not quite feeling 100 percent, but you’re not sure why. Maybe you’re forgetful or feel like you’re moving slowly. That’s brain fog. It’s just a small feeling that you’re not at your best, which can leave even the simplest tasks to feel overly taxing.

Brain fog is temporary. Sometimes it clears with a cup of coffee or a good night’s rest. Other times, it may occur when your blood sugar is dipping low and you need something to eat. That’s why intermittent fasting can sometimes be the cause of brain fog. However, once it’s past your fasting window, the brain fog should resolve itself.

Is Brain Fog Dangerous?

Brain fog may feel uncomfortable, but it’s not overly dangerous as long as you’re taking good care of yourself. If you notice you are feeling confused, sit down and try to retrace your steps. You may forget why you walked into a room or zone out on a drive that you don’t remember getting there. While these moments can be disorienting, they aren’t innately harmful.

How Can I Avoid Brain Fog?

As your body gets used to intermittent fasting, instances of brain fog should decrease over time. That said, there are some steps you can take in the meantime to help avoid brain fog until you cross that threshold.

  • Get enough sleep. Sleeping too little can also make you feel confused and disoriented, so making sure you are well-rested can prevent brain fog from occurring during fasting windows.
  • Eat high-value, nutritious foods during your eating windows. Foods that are high in fiber and protein can help you feel fuller longer, making your fasting windows a little easier because you will have a clearer head.
  • Take a break. Sometimes complex tasks during fasting windows can be challenging, so make sure to take breaks when you need them. Go for a walk or simply move on to a less difficult task. This will help you feel less confused.

Ultimately, brain fog will pass, it will just take time. Intermittent fasting may cause brain fog, and there are things you can do to avoid or mitigate the effects of brain fog.

So, Does Intermittent Fasting Cause Brain Fog?

Yes, intermittent fasting can cause brain fog. While annoying, there is nothing inherently harmful about brain fog. As soon as you break your fast and your body starts to process food, the episode will pass. It may also go away after simply resting or taking a break.

If you are worried, you can always consult a doctor to ensure your brain fog isn’t caused by low blood sugar. Those who have diabetes or other conditions that require medical assistance should not begin intermittent fasting without consulting with their doctors first.

At the end of the day, you have to decide if a little brain fog outweighs the benefits of intermittent fasting and make the best choice for you.


  • Can intermittent fasting cause brain fog in everyone?

Brain fog can occur in some individuals during intermittent fasting, but it doesn’t affect everyone. It depends on various factors such as individual sensitivity, fasting duration, and overall health.

  • How long does brain fog typically last during intermittent fasting?

The duration of brain fog during intermittent fasting can vary from person to person. In most cases, it is temporary and lasts only during the fasting window. Once the fasting period ends and the body begins processing food, the brain fog usually dissipates.

  • Are there any ways to prevent or minimize brain fog while practicing intermittent fasting?

Yes, there are steps you can take to reduce brain fog during intermittent fasting. These include ensuring you get sufficient sleep, consuming nutrient-dense foods during eating windows, and taking breaks or engaging in lighter tasks when experiencing brain fog.

  • Can low blood sugar levels be the cause of brain fog during intermittent fasting?

Low blood sugar levels can contribute to brain fog during intermittent fasting, especially if the fasting window is prolonged. It is important to monitor your blood sugar levels and consult a doctor if you have concerns or pre-existing conditions like diabetes.

  • Should I be worried if I experience brain fog during intermittent fasting?

Brain fog, while uncomfortable, is generally not a cause for major concern. However, if you are experiencing severe or prolonged brain fog, it may be beneficial to consult a healthcare professional to rule out any underlying medical issues or to get personalized advice.

Andrew Brewer

Andrew Brewer

Andrew Brewer started to give people the guidance that he never received when he was first starting. His goal is to make your goals achievable and to offer you only the best fasting apps that the internet has to offer. You're not on your own - Andrew and the entire family of reviewers at are here with you every step of the way!