Is Intermittent Fasting Dangerous?

Intermittent fasting involves going without food for certain periods of time, usually between 12 and 36 hours at a time.

There are many different modes of intermittent fasting.

One common and easy program involves narrowing your eating window to just a few hours a day. Instead of eating throughout the day every couple of hours, you would eat all of your day’s calories within a smaller window. You eat between noon and 4 pm and do not eat anything before or after that until the next day’s eating window.

 Intermittent fasting style is eating normally for six days a week, then not eating anything for around 24 hours.

Why Would Anyone Eat This Way?

Your initial assumption might be that people fast to lose weight. “If you want to eat fewer calories, try eating nothing!”

But weight loss is not the primary benefit of intermittent fasting. Intermittent fasting can be helpful for:

  • lowering high blood pressure
  • improving insulin sensitivity (helps prevent and manage type 2 diabetes)
  • better blood sugar control
  • reducing oxidative stress (a cause of cell and tissue damage)
  • reducing inflammation and joint pain
  • improving mood and overall relationship with food

While intermittent fasting is typically safe for most people, there are a few risks you should be mindful of before you try it for yourself.

Lightheadedness and Dizziness

Because of how fasting affects blood sugar and blood pressure, fainting and dizzy spells can occur when you stand up too quickly. Syncope (fainting) can easily lead to severe and potentially life-threatening injury.

To avoid this, be sure to move slowly when changing positions or standing up, and drink plenty of water throughout the day to stay fully hydrated.

If you feel faint or dizzy at any point, sit down immediately and drink some water. This may signify that it is time to end your fast and eat a banana or some other light snack.

Low Energy, Irritability, or Mood Changes

Some people report feeling more irritable, anxious, or depressed when fasting. This is likely due to blood sugar fluctuations and dehydration.

It’s also common for people to feel more fatigued when they’re fasting. On the other hand, other people sometimes report feeling energized and more focused when fasting.


When you are fasting for short periods, malnutrition is not typically an issue, as long as you are eating a healthy diet during the times you do eat.

But malnutrition can become a serious problem if you are fasting for long periods or severely restricting your calorie intake every day.

Do not fast for more than 48 hours without medical supervision. Also, avoid fasting if you are:

  • pregnant or breastfeeding
  • a child or teen
  • older or experience weakness
  • immunodeficient
  • have a history of low blood sugar, low blood pressure, or fainting

Is Intermittent Fasting An Eating Disorder?

Intermittent fasting is not an eating disorder. However, as with any restrictive diet, there is the potential for it to become one.

If your eating style is negatively affecting your health or your ability to live a happy life, it’s essential to seek help from a qualified professional.

When done correctly, intermittent fasting can be a healthy way to improve your overall wellbeing. But for people who are already predisposed to disordered eating, it can be a trigger. If you have any concerns, speak with a medical professional before experimenting with fasting.