Blog Diets Fasting Is Fasting for 24 Hours Once a Week Healthy?

Is Fasting for 24 Hours Once a Week Healthy?

You may already know something about intermittent fasting or even tried one of its common methods. You would be correct in thinking that fasting may be helpful when it comes to weight loss, heart health, metabolic health, or physical performance. Both beginners and advanced fasting enthusiasts can try it as there are different-leveled fasting strategies. 

Today we’re going to concentrate on a 24-hour fast or the Eat-Stop-Eat diet. For sure, it’s one of the challenging methods and not recommended for beginners. This regime involves a full day of fasting once or twice a week. Many people fast from breakfast to breakfast, while others feel more comfortable fasting from lunch to lunch. 

In this article we’ll explore a primary question – is fasting for 24 hours, once a week, healthy? Additionally, we’ll disclose all the potential benefits and drawbacks of the 24-hour fast once a week. Let’s dig in. 

How often should you do a 24-hour fast?

To answer this question, you need to learn about the two approaches to a 24-hour fast: 

  1. Alternate day fasting
  2. Eat-Stop-Eat method

Alternate-day fasting

This entails fasting every other day. Therefore, you either avoid solid food and calorie-containing drinks every other day or allow yourself 500 calories during the fasting period. Hence, you fast for 24 hours more than once per week (10). This way is more extreme than the second option. 

Eat-Stop-Eat method

It involves avoiding solid food and caloric beverages for a full 24 hours, once or twice per week (10). This means you choose one or two days (preferably as hectic as possible) to “enjoy” your 24-hour fasting period. Again, some people allow up to 500 calories or 25% of their energy needs on fasting days, while others fast completely.

Now, how often should you do a 24-hour fast? Your choice will entirely depend on your experience level, your basic goals, and your preferences. 24-hour fasting 3 days a week or more is not sustainable long-term for most people. 

Why? The reality is, with a full-day fast 3 times a week, you won’t be able to get a sufficient amount of nutrients (minerals, vitamins, and protein). In fact, a 24-hour fast once a week is already challenging enough and may lead to fatigue, dizziness, and irritability (10). 

Extending this time will make the situation even more difficult. This is to say, a full-day fast once or twice per week is likely safer than a 24-hour fast 3 days a week. 

Also, studies have been done with participants engaging in 24-hour fasting regimens with one to two 24-hour fasts per week for up to six months, suggesting that this way may be relatively safe for otherwise healthy people (5).

See also
Intermittent Fasting for Men Over 50: Benefits, Possible Risks, and 10 Tips to Boost the Advantages

Please, consult your healthcare provider before trying any type of fasting. A medical doctor will provide essential guidelines based on your condition and any medication use and help you follow the diet safely. 

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Will a 24-hour fast put me in ketosis?

Ketosis is a natural metabolic state where the body primarily burns fat instead of glucose, for fuel (6). Intermittent fasting is one of the effective ways to reach a state of ketosis (6). It is thought that a 24-48 hours fasting period can achieve ketosis (4). However, there are cases where ketosis can be reached through a shorter fast.

Overall, a 24-hour fast may put you in ketosis. 

Still, it’s essential to highlight that Intermittent fasting’s long-term safety and efficacy requires more research. Speak to your doctor first before entering the 24-hour fast regime. 

Does a 24-hour fast shrink your stomach?

A 24-hour fast once a week for weight loss is usually the most common reason to enter this dietary strategy. Let’s face it, most people who start fasting have one goal – they yearn to trim fat from their body, especially around their stomachs. It may sound logical – you eat nothing, therefore, you’ll be trimming your belly fat. Unfortunately it doesn’t work quite like that. 

My answer may frustrate you – one 24-hour fast will not shrink your stomach overnight. In fact, it’s a general myth that cutting down the food intake over a short period can shrink your stomach. If it was true, there would be more fasting admirers. 

No matter whether you’re focusing on Bone Broth Fasting or Fasting Detox, your stomach won’t magically become thinner. You’ll need to create a calorie deficit over time by eating less than you burn, increasing physical activity, and being patient. (2).

Pondering losing belly fat? Use healthy strategies, which include (1): 

  • Staying active. Do workouts, run, ride a bicycle, and do anything that keeps you moving. 
  • Add strength training to your routine. 
  • Avoid ultra processed/sugary foods.
  • Sleep well. 
  • Drink enough water. Besides, drinking water may reduce your hunger. 
  • Eat healthier food. Your beneficial eating plan should include veggies, fruits, whole grains, and lean proteins, and healthy fats. 
See also
Intermittent Fasting Coffee: 7 Tips For Making It Perfect

Trimming belly fat is hard but possible with the combination of all the aforementioned strategies. And yes, you may have heard of them dozens of times because they are effective and healthy. So, why not implement this into your life? 

fasting for 24 hours once a week  

What happens to your body after 24 hours of fasting?

When you go without food for 24 hours, your body will start digesting your last meal and absorbing all the nutrients within 6-8 hours. At this point your body uses its glucose stores to get energy. 

After the overnight fast, glycogen stores in your body will start to become depleted, hence, leading to the breakdown of fat reserves (8).

This allows your body to burn mostly fat for energy as your stored fat becomes more available to use. This phenomenon, scientifically, is called ketosis. 

What are the benefits of a 24-hour fast?

There is no surprise that the benefits of a 24-hour fast once a week are possible if you stick to healthy dietary choices during non-fasting days. Those potential benefits are:

  1. You may improve your insulin sensitivity
  2. You might promote your heart health
  3. You may enhance metabolic health
  4. You may improve the cognitive functions of the brain
  5. You may reduce body fat

You may improve your insulin sensitivity

In one study, 103 participants practiced 24-hour fasting twice a week for 4 weeks followed by a 24-hour fast once a week for 22 weeks. The study found an improvement in insulin sensitivity in the fasting group (9).

You might promote your heart health

Another potential advantage of 24 hour-fast is reduced risk of heart disease. A study in 2018 revealed that fasting for 24 hours temporarily decreased the levels of a compound called TMAO (trimethylamine N-oxide). This compound is produced by intestinal bacteria and may elevate the risk of heart disease (3). This requires much more research to understand its significance. Studies on this and other types of intermittent fasting which have investigated blood lipid levels, another risk factor for heart disease, have found mixed results. 

You may enhance metabolic health

Metabolic syndrome involves metabolic alterations that increase your risks of heart disease, stroke, and type 2 diabetes. However, a study in 2021 stated that people performing water-24-hour fasts twice weekly for four weeks and then once weekly for 22 weeks significantly lowered their Metabolic Syndrome Score (MSS) (9).

You may improve the cognitive functions of the brain

Intermittent fasting for 24 hours has been observed to enhance the cognitive functioning of the brain in animals. It is thought to possibly help protect the long-term health of their brains, as well as prevent Parkinson’s, Alzheimer’s, and other diseases later in life (7).

See also
Time-Restricted Eating vs Intermittent Fasting: Are They The Same?

You may reduce body fat

The major effect of 24-hour fasting is on your body composition. Studies report that intermittent 24-hour fasts can reduce body weight and fat in people with normal weight as well as overweight people (5).

Read more: Intermittent Fasting Cortisol: Should You Fast?

What are the rules for 24-hour fasting?

As with any other fasting regime, a 24-hour fast has its rules to follow. They are important because they help you to attain the desired results without harmful consequences. 

Here are a few basic rules of 24-hour fasting. 

Rule#1 Consume calorie-free food during the fasting period

One mistake that people often make is not eating and drinking anything during fasting. This is incorrect. You can drink beverages, like plain water, unsweetened tea, black coffee, and other non-caloric drinks. Intermittent Fasting Coffee would not involve milk, sugar, or syrups, as these will break your fast. 

Rule#2 Eat smartly on non-fasting days

So, you haven’t eaten anything the whole day and a sudden thought pops into your head – “Why not allow me more meals today than I usually eat? I deserve it, right?”. In fact, there are individuals who think that way and indulge in high-caloric meals. 

In the best-case scenarios these meals are healthy. In the worst-case scenario, it’s all about junk food. Instead, you should consume your meals in the same quantity you usually enjoyed before entering the 24-hour fast twice a week, or once a week.  

Rule#3 Make your fasting day as engaging as possible

Lying on your bed, hungry the whole day will make you miserable: your thoughts are hovering around lavish desserts, tasteful pizzas, and other desirable dishes. You will have these thoughts as you have nothing else to do. 

To eliminate the problem, tackle your day with engaging activities: meet your friends, stroll in the park, read a book, watch a movie while drinking water, or have a bike ride. Do something that takes over your attention instead of imposing your thoughts about your favorite meals. 

fasting for 24 hours once a week  

Rule#4 Be prepared to feel unwell at the beginning and stop on time

It should be no wonder that eating no food for one day is difficult and surely affects your both physical and emotional state. A certain amount of hunger and irritability is to be expected. . More about the drawbacks in the next segment. 

See also
How to Fast Properly to Reap Wellness Rewards

Yet, if you feel like its effects are too harmful to you, better stop the process to not make things even worse. The truth is, this method is not for everyone, and don’t get frustrated if you give up quickly. 

By the way, you could switch to a milder fasting regimen, such as 12 12-hour per day fast or fasting for 16 hours. 

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What are the bad effects of fasting?

Water fasting once a week has certain side effects and complications due to its intensive nature. Why? As you abstain from solid food, you don’t get enough nutrients that sustain your well-being. It can lead to potential side effects that will impact your physical, mental, or emotional state. 

The most common consequences include

  • increased hunger pangs
  • dizziness
  • fatigue
  • irritability
  • mood swings
  • sleep troubles 

Therefore you should pay close attention to your water consumption so that you aren’t dehydrated after an extended 24-hour fast. Drinking enough water will help you keep your hunger at bay. Again, it’s always recommended to consult your doctor before starting a new fasting regimen or changing your current plan.

Besides, there are people who should avoid fasting regimes: 

  • Those who have an underlying medical condition, such as diabetes, or who are on certain medications
  • Pregnant and breastfeeding females
  • Children under 18 years
  • People with a history of eating disorders

Read more: How Your Fasting Windows Can Make Or Break Your Intermittent Fasting Experience


Is it OK to fast once every week?

It is okay for most healthy people to fast once every week. It was already said that a 24-hour fast once or twice per week for up to six months is relatively safe and won’t put you at risk of major side effects. Nonetheless, you should talk to your doctor before entering in a new fasting regime, as it is not appropriate or safe for everyone. 

Is fasting for one day a week healthy?

Fasting for one day a week might boast a great number of benefits: it may improve your insulin sensitivity, it might promote your heart health, may enhance metabolic health, may improve the cognitive functions of the brain, and may reduce body fat. 

See also
Benefits of Intermittent Fasting for Women With Expert Tips to Reap Them Without Setbacks

Will I lose muscle if I fast for 24 hours?

24-hour fasting can promote weight loss over time and when you lose weight, you typically lose both fat mass and lean mass, especially if you lead a sedentary lifestyle. However, intermittent fasting does not cause more muscle loss than other weight loss diets. Therefore, a 24-hour fast is unlikely to cause significant lean body mass. You can minimize this by eating plenty of protein during your eating windows and doing strength training exercises.  

Can fasting reset your metabolism?

Fasting leads to metabolic adaptations, such as switching to burning fat once stored carbohydrates are depleted. As fasts go on, the body eventually enters starvation mode where the focus shifts to conserving energy to survive. When you eat again, your metabolism goes back to using the energy from the food you eat, primarily in the form of glucose.

The Bottom Line

Is fasting for 24 hours once a week healthy? Hopefully you got your answer to this question. Let’s wrap it all up again. 

A 24-hour fast entails avoiding solid food and caloric beverages for a full day once or twice per week. During the fasting period,  you are allowed to drink water, unsweetened coffee, and herbal tea. Some people do a modified version of this and allow themselves up to 500 calories or 25% of their energy needs on fasting days. 

Fasting for 24 hours once a week is relatively safe for most healthy people but you should consult a doctor instead of experimenting with this regime on your own. People with certain medical conditions, who are taking certain medications, who are pregnant or breastfeeding, or who have a history of eating disorders should not fast.

A 24-hour fast can put you in a state of ketosis. When it comes to stomach shrinking, intermittent fasting on its own will not trim your belly fat. The benefits of 24-hour fasting may include: promoted heart health, better insulin sensitivity, enhanced metabolic health, improved cognitive functioning of the brain, and reduced body fat. 

The four common fasting rules involve consuming calorie-free food during the fasting period, keeping yourself busy on fasting days, eating healthily on non-fasting days, and stopping the process when feeling unwell. 

A 24-hour fast may have side effects consisting of dizziness, fatigue, mood swings, irritability, or problems with sleep. There are types of people who should abstain from any fasting regime for their own safety. 


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!


  1. 8 Ways to Lose Belly Fat and Live a Healthier Life (
  2. 9 Surprising Facts About Your Stomach (2013,
  3. Abstract 13412: 24-Hour Water-Only Fasting Acutely Reduces Trimethylamine N-Oxide: the FEELGOOD Trial (2018,
  4. Advantages and Disadvantages of the Ketogenic Diet: A Review Article (2020,
  5. Effects of intermittent fasting on body composition and clinical health markers in humans (2015,
  6. How to get into ketosis faster (2023,
  7. Intermittent fasting and cognitive performance – Targeting BDNF as potential strategy to optimise brain health (2022,
  8. Physiology, Fasting (2023,
  9. Randomized controlled trial of once-per-week intermittent fasting for health improvement: the WONDERFUL trial (2021,
  10. Six ways to do intermittent fasting (2023,
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