Why Do I Feel Sleepy During Intermittent Fasting?

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

why do i feel sleepy during intermittent fasting

Intermittent fasting has many benefits, including weight loss, lowered risk of heart disease, and improved blood sugar. However, it’s not always easy riding as you get acclimated to your new eating style. One of the most common side effects of intermittent fasting is sleepiness and feeling fatigued. While it’s uncomfortable, you’ll realize the benefits outweigh the cost once you make it through.

Key Takeaways

  • Feeling tired and fatigued during intermittent fasting is a normal part of the process as your body adjusts to a new eating style.
  • Drinking enough water and eating strategically during your eating windows can help you manage fatigue and maintain energy levels.
  • Breaking your fast slowly with small, nutrient-dense meals can help you avoid discomfort and energy crashes.
  • Severe symptoms of fatigue may require medical attention, so it’s essential to consult with a healthcare professional if needed.
  • Intermittent fasting can have numerous benefits, including weight loss, improved blood sugar levels, and a lowered risk of heart disease.

Why Am I Tired?

You get energy from the food you consume, so if you’re not eating anything, you’ll likely feel tired – at least at first. Many people report feeling fatigued and having low energy levels during intermittent fasting. This is probably a result of the low blood sugar levels. You may even notice yourself having difficulty falling asleep or staying asleep, making you feel even more tired during the day.

The good news is that these feelings of overwhelming tiredness do not last, and there are ways to help you manage your fatigue.

How to Overcome Intermittent Fasting Fatigue

Taking a nap isn’t always possible, so here are some tried and true tips to help you manage your exhaustion as you acclimate to intermittent fasting.

Drinking More Water

You may be tempted to go straight to the caffeine when you’re tired. After all, it will help give you that quick boost of energy you need to keep going. Before you grab the mug, try drinking a glass of water. Tiredness and fatigue can also be side effects of dehydration, so you may not be drinking enough fluids.

This is especially important during your fasting windows because you’re not getting any water content from your food. That’s not to say you can’t have coffee or tea. Just make sure to balance it with water.

Eat Better

This may be counter-intuitive because you’re not actively eating, but what you eat during your eating windows impacts how you feel when fasting. High protein, fiber-full foods will help give you more energy as you fast while still burning fat. Eat lots of foods, vegetables, nuts, grains, and lean proteins for the best results.

You’ll notice a difference in your fast days when you eat strategically, focusing on the nutritional content rather than what your body may be craving. Over time, your body will start to crave healthy foods. You’ll no longer crave junk, though it is okay to indulge now and then! You’ll find that foods you used to love won’t taste as good as they used to once you retrain your way of eating.

Don’t Overeat

After a fast, you may be tempted to eat as fast as possible; however, resist the urge. You’ll thank yourself later. If you do, it will put you into a food-coma-like state. While it may feel good at first, your body needs time to catch up on eating. Eating too much too fast will shock the system, causing discomfort. You may crash or experience diarrhea or constipation.

Instead, break your fast slowly. Remember to pay attention to the nutritional content of your food for the best result. Low carb, small meals will be your best bet to avoid energy crashes.

So, Is Feeling Tired Normal During Intermittent Fasting?

Yes, feeling tired and fatigued during intermittent fasting is a normal part of the process. You are teaching your body a whole new way to eat and process your food, so there will be a learning curve.

You can push through the fatigue by staying hydrated and eating strategically to set yourself up for success during your eating windows. And, when in doubt, you can grab a cup of coffee or tea for an immediate energy boost.

Don’t forget to check our 10 best intermittent fasting apps to make your intermittent fasting journey easier.


  • Why do I feel sleepy during intermittent fasting?

It is common to feel sleepy during intermittent fasting because your body is experiencing a change in energy levels and blood sugar regulation. Additionally, your body is using its energy reserves differently, which can cause feelings of fatigue.

  • What are some ways to combat sleepiness during intermittent fasting?

To combat sleepiness during intermittent fasting, staying hydrated and consuming nutrient-dense foods during eating periods is important. Also, getting enough sleep, reducing stress, and engaging in light exercise can help to increase energy levels.

  • Can intermittent fasting cause long-term sleep problems?

Intermittent fasting is unlikely to cause long-term sleep problems, but it is important to ensure that you get enough restful sleep during eating and fasting periods. If you experience persistent sleep disturbances, talking to a healthcare professional is important.

  • Is it normal to experience changes in energy levels during intermittent fasting?

Yes, it is normal to experience changes in energy levels during intermittent fasting. Your body is adjusting to using stored energy during fasting periods and may experience fluctuations in blood sugar levels. However, if you are experiencing extreme fatigue or other symptoms, talking to a healthcare professional is important.

  • How long does it take for the body to adjust to intermittent fasting?

The amount of time it takes for the body to adjust to intermittent fasting can vary from person to person. Some individuals may adapt within a few days, while others may take several weeks. Therefore, it is important to listen to your body and make adjustments as needed to ensure that you are maintaining your overall health and well-being.

Andrew Brewer

Andrew Brewer

Andrew Brewer started Fastingapps.com 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 Fastingapps.com are here with you every step of the way!