Everything You Need to Know About 24-Hour Fasting

Woman trying 24-hour fasting

Fasting is an ancient practice that’s still popular in many circles today, including with most wellness enthusiasts. It involves restricting food for specified periods of time. This can be a complete temporary elimination of food (water fasting) or simply caloric restriction. One of the most popular versions is a 24-hour fast once a week

Fasting is no easy feat. It can take immense willpower and discipline, but it can be well worth the effort when practiced wisely and with the right intentions. 

Healthy fasting has the potential to lead to positive body composition changes, improved mental clarity, better heart health, better physical endurance, and a longer life. If these changes interest you, keep reading to find out how to safely practice fasts, how they affect the body, and who can benefit from them.

The Benefits of 24 Hour Fasts

If you’ve taken into account your personal situation and decided 24 hour fasts are something you can healthfully undertake, you may still be wondering what exactly is in it for you. Different lengths of fasting can bring about specific benefits, and a 24 hour fast is a relatively extreme fast that can bring about some unique bodily changes. 

Here’s what you can expect:

Hours 0-4

  • Your body will use up most or all of the energy from the food use recently eaten (depending on the size of the meal)
  • This energy will be in the form of glucose in the bloodstream

4-16 Hours

  • Your body will switch from food-derived energy to tapping into your energy stores
  • This energy will come first from glycogen in the liver, and when that runs out, you’ll begin burning body fat stores instead (ketosis)
  • Autophagy (where old and unhealthy cells are removed from the body) can also begin at this stage

Hours 16-24

  • Your body will be in complete ketosis (fat-burning mode), which can result in weight loss
  • Cell renewal through autophagy will increase
  • Human growth hormone levels will rise, which increases cognitive abilities and lower stress

If you’ve accomplished a full 24-hour fast, you’ll likely be feeling clear-headed, have no gut discomfort from inflammatory foods, and be full of energy from the fat you’ve been burning for energy.

The undoubtedly positive results may tempt you to fast more often than doctors recommend. However, the benefits can quickly give way to the negative impacts of too much fasting, so use care when performing 24-hour fasting.

How Often Can You Practice 24-Hour Fasts?

According to research from 2021 in the European Heart Journal, you can engage in 24-hour fasting 1-2 times per week for extended periods of time in healthy subjects with no ill effects. 

The fasts studied in this paper included water fasts done by participants between the ages of 21-70 years old, which implies that people of all adult ages can enjoy the benefits of fasting.

Some people also practice alternate-day fasting (every other day with no food), with anecdotal evidence stating its benefits, but we cannot recommend it due to far less clinical data supporting its safety.

Who Shouldn’t Fast

Before delving into the specifics of fasting, it’s essential to know how fasting could be harmful for. Firstly, growing children and teenagers are never recommended too fast. This could seriously impact their long-term health since their body requires a consistent supply of nutrition for optimal health at this stage of life.

Secondly, pregnant and nursing women should never intentionally fast. Their bodies are supporting the growth of another vulnerable human at this stage, and there can be harmful impacts on both the mother and child if they’re not nourished properly with regular caloric intake.

A third demographic that would be wise to avoid fasting is anyone currently struggling with or with a history of eating disorders. Fasting involves food restriction, and this behavior will be extremely triggering for anyone who struggles with body image issues. They won’t be able to manage a fast in a physically or mentally healthy way, so it’s not recommended. Anyone who’s underweight—eating disorder or not—will also likely see more negative than positive effects from fasting.

Finally, fasting is not a safe practice for anyone with diabetes. Those with diabetes need to pay careful attention to their blood sugar levels, and this will be difficult, if not impossible, to do while following most fasting protocols.

How to Fast in a Healthy Way

If none of the above groups mentioned apply to you, fasting could potentially be a health-boosting practice. There are many different types of fasting that work best for each unique individual. The most important thing is always to listen to your body and act intuitively. If you feel lightheaded, ill, or too uncomfortable to continue, whatever fast you’re practicing should be stopped immediately. 

One of the most popular and simple methods of fasting is a 24-hour fast. This means 24 hours with no calories, just water and herbal teas, electrolytes, and black tea or coffee if desired. 

This is a relatively intense form of fasting, so it may be best to slowly work up to this goal. A few ways to prepare are to practice shorter fasts starting at just 12 hours and slowly working your way up to 24. You should always take breaks in between your fasting and pay attention to your overall energy levels. If you don’t have good amounts of energy, you’re likely not eating enough overall and doing more harm than good with your fasting.

A second way to work up to a 24-hour fast is to practice caloric restriction instead of completely abstaining from food. You could cut back your usual calorie intake to 1000 calories and then gradually lower it over time. Again, this should never be practiced daily. This is simply a tool to be used on occasion to reap the health benefits of fasting without lowering total weekly calories below a nourishing level.


Overall, 24-hour fasts are safe for most people if proper planning and considerations are taken into account. It can be a healthy practice that improves metabolic health and mental focus and results in a healthy body composition. 

As long as these fasts are practiced intermittently with a balanced, nourishing diet inbetween, the positives far outweigh the potential drawbacks.

Photo by Mikhail Nilov on Pexels


Please enter your comment!
Please enter your name here

This site uses Akismet to reduce spam. Learn how your comment data is processed.