Not eating for 24 hours at a time is a form of intermittent fasting known as the eat-stop-eat approach.

During a 24-hour fast, you can only consume calorie-free beverages. When the 24-hour period is over, you can resume your normal intake of food until the next fast.

In addition to weight loss, intermittent fasting can have a positive effect on your metabolism, boost cardiovascular health, and more. It’s safe to use this approach once or twice a week to achieve your desired results.

Although this technique may seem easier than cutting back on daily calories, you may find yourself quite “hangry” on fasting days. It can also cause severe side effects or complications in people with certain health conditions.

You should always talk to your doctor before going on a fast. They can advise you on your individual benefits and risks. Keep reading to learn more.

You’ll be well into your 24-hour period before your body realizes that you’re fasting.

During the first eight hours, your body will continue to digest your last intake of food. Your body will use stored glucose as energy and continue to function as though you’ll be eating again soon.

After eight hours without eating, your body will begin to use stored fats for energy. Your body will continue to use stored fat to create energy throughout the remainder of your 24-hour fast.

Fasts that last longer than 24 hours may lead to your body to start converting stored proteins into energy.

More research is needed to fully understand how intermittent fasting can affect your body. Early research does suggest a few benefits, though.

It can help with weight loss

Fasting one or two days a week may be a way for you to consume fewer calories over time. You may find this easier to do than cutting back a certain number of calories every day. The energy restriction from a 24-hour fast may also benefit your metabolism, helping in weight loss.

It can help you manage your cholesterol and sugar levels

Regular intermittent fasting may help improve how your body breaks down cholesterol and sugar. These changes to your metabolism may help reduce your risk of developing conditions like diabetes and cardiovascular disease.

It may help reduce your risk for coronary artery disease

A regular 24-hour fast may help reduce trimethylamine N-oxide levels in the long term. High levels of this compound are tied to coronary artery disease, so this may help reduce your risk.

Other benefits

Intermittent fasting may also help:

  • reduce inflammation
  • reduce your risk of certain cancers
  • reduce your risk of neurological conditions like Alzheimer’s and Parkinson’s disease

Frequently fasting for 24-hours at a time can lead to side effects and increase your risk for certain complications.

Always talk to your doctor before going on a fast to help reduce your risk for any unforeseen health consequences. This is particularly important if you have underlying health conditions.

You shouldn’t fast if you:

  • have or have had an eating disorder
  • have type 1 diabetes
  • are pregnant or breastfeeding
  • are under age 18
  • are recovering from surgery

Fasting more than twice per week may increase your risk for heart arrhythmias and hypoglycemia.

Keep in mind that more research is needed to fully assess the potential benefits and risks of intermittent fasting. Exercising regularly and eating a balanced diet are proven methods to living a healthier lifestyle and maintaining your weight.

It’s important that you drink plenty of water — more than your usual eight glasses — during a 24-hour fast.

You won’t be ingesting any water from food during this time, and your body needs water to function. Water helps your body’s digestive system, regulates your body temperature, benefits your joints and tissues, and can keep you feeling energized.

You should drink water as you feel thirsty throughout the day. This amount varies from person to person and depends on your activity level as well.

One older guideline says that, on average, men should drink around 15 1/2 glasses of water and women should drink around 11 1/2 glasses of water per day. Ultimately, your thirst should be your guide when it comes to water intake.

You can perform a 24-hour fast whenever you choose. You just have to make sure that you prepare for your fasting day in advance. Eating healthy and well-rounded meals prior to the fast will help your body get through the 24-hour period.

Some foods you should consider eating prior to a fast include:

  • foods rich in protein, such as nut butters and beans
  • dairy products low in fat, such as low-fat yogurt
  • fruits and vegetables
  • whole-grain starches

Foods high in fiber will help your body feel full long after eating. Fruits and vegetables contain water, giving you more hydration.

Drink water and other calorie-free beverages during the fast, but keep in mind that beverages with caffeine may cause you to lose more water. Drink an additional cup of water for every caffeinated beverage to help balance your intake.

Continue to eat healthy after your fast is over and avoid overeating when it’s time to eat again. You may want to have a small snack or eat a light meal when your fast ends to help you ease back into your regular eating routine.

Be cautious when trying this approach. Talk to your doctor about your health before attempting it on your own. Your doctor can talk to you about your individual benefits and risks, as well as advise you on how to conduct this type of fast in a healthy and safe way.