Intermittent Fasting Side Effects

Intermittent Fasting Side Effects

Written by Andrew Brewer. ⚕️Reviewed and fact checked by Dr. Kimberly Langdon.

Intermittent Fasting Side Effects

As with all good things, too much of it can be a bad thing. Intermittent fasting is no exception to this rule. If you fast for too long or too often, your body is bound to experience some negative side effects. These side effects can be as minute as stomach cramps or as drastic as severe malnutrition.

If you’re not careful, you could quickly find yourself struggling with headaches or dehydration if you over-fast. Intermittent fasting offers tons of incredible benefits to the body and is a fantastic weight-loss tool to have in your arsenal, but again, too much of a good thing quickly becomes a bad thing.

Let’s take a look at some of the negative side effects that your body is at risk of when intermittent fasting. These issues are dependent on many factors aligning and won’t be an issue if you take care of yourself whilst fasting. If you have certain preexisting diseases, are pregnant, or have a history of eating disorders, then you may be at a higher risk of experiencing these side effects.

Talk to your primary care physician if you have any concerns about intermittent fasting.

Key Takeaways

  • Intermittent fasting can offer numerous benefits, such as weight loss and improved metabolic health, but it is important to be mindful of potential negative side effects.
  • Some common side effects of intermittent fasting include hunger cravings, fatigue, difficulty sleeping, and decreased mental wellness. More severe side effects, such as dehydration and malnutrition, can also occur if fasting is taken too far.
  • Intermittent fasting may not be suitable for everyone, particularly individuals with certain medical conditions or who are pregnant. Consulting with a healthcare professional before starting an intermittent fasting regimen is recommended.
  • Despite the potential side effects, many people find intermittent fasting to be a helpful tool for improving their health and well-being. Careful attention to hydration, nutrition, and gradual adjustments to fasting can help to minimize side effects and maximize the benefits.
  • It’s essential to listen to your body and pay attention to how you feel during intermittent fasting. If you experience any negative side effects, it may be time to adjust your fasting schedule or consult with a healthcare professional.

Cravings Stick Around

One of the first side effects of intermittent fasting that you may experience is cravings. This is one of the smaller issues, but it’s one that can directly impact your ability to fast. Sometimes cravings and hunger can unite to create a powerful team that derails your intermittent fast.

When you want that bag of chips late at night, it takes a strong mind to tell yourself no. These side effects are quite common and vary based on the type of intermittent fasting you’re trying. Hunger can be a tough obstacle to overcome, but at least you’re not alone in this intermittent fasting side effect.

Mental Wellness Decreases

I’m sure at one point or another in our lives, we’ve experienced hunger anger. Being “hangry” is a normal thing that affects everyone – intermittent fasting or not. However, when intermittent fasting, your risk of getting hangry can greatly increase.

Many who intermittent fast have reported worse episodes of hanger, and more frequent bouts of it. Your body tends to react poorly to being malnourished and often times mistakes lower caloric intake as being malnourished.

Other side effects of intermittent fasting include fatigue throughout the day and generally low energy. Depression is another mental illness that could be emboldened by intermittent fasting.

Trouble Sleeping

While you may be fatigued throughout the day, intermittent fasting could cause difficulty sleeping. Besides hunger and cravings, difficulty getting to sleep and staying asleep is one of the most common side effects of intermittent fasting.

While it is a common side effect, it isn’t guaranteed that you’ll experience difficulty sleeping. Some people who are dedicated intermittent fasters have reported better sleep when starting and throughout the process.

Dehydration or Malnutrition

Not all of the side effects of intermittent fasting are as simple as lifestyle changes. Some can be quite dangerous if not taken care of properly. If you begin to show signs of dehydration or malnutrition, then perhaps you should decrease the amount of fasting you do.

Dehydration and malnutrition can be signs that your body isn’t getting the nutrients it needs to operate throughout the day. Whether this is because you’re fasting too much or you’re not eating the right foods once you break your fast, dehydration and malnutrition can be dangerous.

Avoid Intermittent Fasting if You…

Some people are more prone to these negative side effects than others. You should avoid intermittent fasting if you:

  • Are pregnant
  • Are a young child or teen
  • Are prone to eating disorders
  • Are subject to preexisting conditions like diabetes

There are many more factors that could cause these negative intermittent fasting side effects. We recommend checking with your doctor before starting intermittent fasting.

If you are planning to start intermittent fasting and want to make everything a lot simpler, we would like to recommend you to check out this list for the best intermittent fasting apps available in the market.


  • What are the possible side effects of intermittent fasting?

Some possible side effects of intermittent fasting include hunger, irritability, headaches, dizziness, fatigue, and difficulty concentrating.

  • How can I manage hunger during intermittent fasting?

Drinking water and staying busy with work or other activities can help manage hunger during intermittent fasting.

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

It can take several weeks for the body to adjust to intermittent fasting, but the length of time can vary from person to person.

  • Can intermittent fasting cause dehydration?

Yes, intermittent fasting can cause dehydration if you do not drink enough water during fasting.

  • Is it safe to exercise during intermittent fasting?

Yes, it is generally safe to exercise during intermittent fasting, but it is important to listen to your body and not push yourself too hard.

  • What should I eat during the eating periods of intermittent fasting?

During the eating periods of intermittent fasting, it is important to focus on nutrient-dense foods like fruits, vegetables, whole grains, lean protein, and healthy fats.

  • Can intermittent fasting lead to eating disorders?

Intermittent fasting can trigger disordered eating behaviors in some individuals, especially those with a history of eating disorders.

  • Is intermittent fasting safe for everyone?

Intermittent fasting may not be safe for everyone, especially pregnant or breastfeeding women, individuals with a history of eating disorders, and those with certain medical conditions. It is important to consult with a healthcare professional before starting an intermittent fasting regimen.


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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!