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Benefits of a 24-Hour Fast Once a Week 

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Melissa Mitri post Reviewer Melissa Mitri post Reviewer
Verified by Melissa Mitri
MS, Registered Dietitian, Former President of CT Academy of Nutrition & Dietetics

Table of Contents

Intermittent fasting is a popular dietary regimen that revolves around pre-determined fasting and eating periods. Although it was not originally used as a weight-loss method, studies suggest that it can help people effectively lose 7-10 pounds in 10+ weeks [1]

You can choose the length of fasting window you prefer. Some people opt for shorter fasting durations, while others go for longer periods, such as 24 hours. 

Are there any advantages to these extended fasts? What are the benefits of a 24-hour fast once a week? That’s what we’re going to address in today’s post. 

What You Should Know About a 24-Hour Fast

What happens when you go without food for 24 hours? 

After you stop eating, your body will digest most of the food you ate within 6-8 hours [2]. By the 24-hour mark, glycogen stores in your body will be depleted, forcing the breakdown of fat reserves [3]

This phenomenon is called ketosis, which is how we benefit from intermittent fasting. Ketosis can sometimes happen as early as 12 hours into fasting [1]

If you want to follow a 24-hour fast, there are two main approaches you can try.

  1. Alternate-day fasting, in which you fast every other day, alternating between fasting and eating days. This method involves fasting for a 24-hour period more than once a week.
  2. The Eat-Stop-Eat method in which you fast for a full 24 hours once or twice per week.

You can choose how many days you will be fasting per week depending on your experience level and your preferences. In this post, we will be focusing on the benefits of fasting 24 hours once a week.

What can you have on a 24-hour fast?

Similar to other IF regimens, you can only consume foods or drinks that are calorie-free within the fasting period. Your options include water, unsweetened tea or black coffee, herbal teas, and other beverages that don’t introduce calories into your body. 

In some modified 24-hour fasting regimens, you can eat up to 500-600 calories during the 24-hour period.

5 Benefits of 24-Hour Fasts Once a Week

Intermittent fasting has been shown to bring about various benefits, but the advantages of longer fasts may vary from shorter fasts. Here we discuss the scientifically proven benefits of 24-hour fasts once a week. 

Improved insulin sensitivity

One study followed 103 participants practicing 24-hour fasting twice a week for 4 weeks followed by a 24-hour fast once a week for 22 weeks. In this study, improvement in insulin sensitivity was observed in the fasting group [4].

Enhanced metabolic health

In the same study we discussed above, the researchers evaluated the effect of fasting on Metabolic Syndrome Score (MSS). MSS is a predictive score that gives an idea of metabolic syndrome status. Metabolic syndrome is a cluster of metabolic conditions such as obesity, heart disease, and diabetes that can negatively impact health.

This study revealed that MSS was significantly reduced in the fasting group while the control group showed an increase in its MSS score [4].

Better lipid profile

Whole-day fasts lasting between 12-24 hours have been shown to reduce total blood cholesterol and triglyceride levels [5]. While shorter fasts have also been reported to reduce blood lipid levels [6], longer fasts, like 24-hour fasts once a week, can be more effective as they allow you to be in the ketosis state for longer, thus oxidizing fat for extended periods. 

Improved heart health

Another benefit of not eating for 24 hours is reduced risk of heart disease. In a study conducted in 2018, it was revealed that fasting for 24 hours reduced the levels of a certain compound called TMAO (trimethylamine N-oxide), which increases the risk of heart disease [7].  

Reduction in weight and body fat

Studies also report that 24-hour fasts can reduce body weight and body fat in people who are normal weight, overweight, or obese [5]. We will discuss how you can lose weight by doing a 24-hour fast once a week in a later section of this article.

Is Fasting One Day a Week Enough?

While some of the research studies discussed here are related to alternate-day fasting, we can assume that the benefits more or less translate to once-a-week 24-hour fasting as well.

However, this doesn’t mean that you need to practice extended fasting in order to reap the benefits of intermittent fasting. 

Some of the available research shows that even relatively shorter fasts can be beneficial as long as you’re consistently sticking to your fasting routine.

Side Effects and Restrictions

Although there are several benefits to 24-hour fasting, certain side effects and complications can also occur due to the intensive nature of it. They include increased hunger pangs, dizziness, and fatigue. 

If you don’t pay close attention to your water intake, you might also get dehydrated after an extended 24-hour fast. You may also experience irritability, mood swings, and trouble sleeping due to extreme hunger. 

Pro tip: You can keep your hunger at bay by drinking lots of water while fasting. 

You should always talk with your doctor or nutritionist before starting a new fasting regimen or changing your current plan. This especially applies if you have an underlying medical condition such as diabetes, if you’re pregnant or breastfeeding, or if you have a history of eating disorders. 

Children under 18 should also take caution when practicing a fasting protocol that lasts for 24 hours. 

Even if you don’t have a medical complication, you might still feel that it’s not for you if such prolonged fasting makes you uncomfortable. In that case, you can try a more tolerable fasting method, such as 18/6 or 12/12, and still enjoy many of the benefits of intermittent fasting. 

Can You Lose Weight by Fasting One Day a Week?

Before answering this question, we would like to give you a little bit of background knowledge first. 

To lose weight, you need to burn more calories than you consume. In short, you need to be in a calorie deficit. The calorie deficit you can achieve by fasting for an entire day depends on the number of calories you eat per day. 

Let’s say you consume 2,000 calories a day. That means you will create a shortage of 2000 calories if you fast for a day. Typically, you need to burn 3500 calories in order to lose 1 pound of fat. If you do one 24-hour fast during the week, you will burn a little more than half a pound of fat within that week. 

This means that how much weight you can lose in a 24-hour fast depends on your typical daily calorie intake. However, this only applies if you eat within your daily calorie limit during the rest of the days of the week.

For instance, if you fast for one day of the week but exceed your calorie limit on the other days, you will not be in a calorie deficit. Such a situation will lead to weight gain rather than weight loss.

How Long Can You Safely Practice 24-Hour Fasts?

If you’re generally healthy and have enough willpower to sustain a prolonged fast, you may be able to do a 24-hour fast once a week for an extended period without any adverse effects. 

Studies have confirmed there are no side effects or negative outcomes of practicing a 24-hour fasting regimen once a week for up to 22 weeks (around 6 months) [4]. However, studies also note that the dropout rate is higher in these extended-hour fasting trials, implying they can be hard to commit to [4].

Always consult with your doctor or a registered dietitian before implementing fasting in your routine.

Wrapping Up

Incorporating a 24-hour fast once a week offers several benefits as well as some mild setbacks. You can lose weight by fasting one day a week but you need to stick to your calorie intake for the rest of the week. 

How often you should fast for 24 hours within a week depends on your resilience level, but it’s best to limit it to once or twice per week in order to meet your nutritional needs. 

Disclaimer This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!

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