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How to Do a 24-Hour Fast for Effective Weight Loss

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  Published on January 13th, 2023
  Reading time: 12 minutes
  Last modified January 13th, 2023
24-hour fasting for weight loss

A 24-hour fast, also known as eat-stop-eat, is an advanced intermittent fasting approach that drastically reduces your caloric intake by requiring you to abstain from food for 24 hours. Prolonged fasting in this way can allow your body to enter starvation mode, which has been linked to various health benefits.

If you are new to extended fasting for weight loss, it’s important to familiarize yourself with the dos and don’ts of this approach. In this article, we will discover how to get the most out of your 24-hour fast, along with tips for success.

What Is a 24-Hour Fast, and How Is It Done?

A 24-hour fast is a form of intermittent fasting in which you go without eating for a full day. There are several approaches to this time-restricted eating pattern, but the most common is to follow your regular diet for a few days, then fast for 24 hours before returning to your routine. The cycle can then be repeated, depending on your needs and your tolerance. 

People often follow this fasting plan to reduce body fat or weight. Before starting the eat-stop-eat diet, it’s vital to prepare by eating healthy, nutritious meals like dairy products, protein-rich foods, whole-grain starches (avoid these if you’re following a keto diet), and fruits and vegetables. Doing this will help you get through the 24-hour fasting period smoothly.

During the fast, you should avoid solid foods and stick to zero-calorie beverages like water, black coffee, and herbal tea. Low-calorie liquids like coconut water or broth can be consumed in certain circumstances and in limited amounts to avoid breaking your fast.

How often you should do a day of fasting depends on your individual goals, lifestyle, and overall health. Many people do it once a week, while other people do it once or twice a month if their lifestyles and bodies allow it.

What Happens to Your Body During a 24-Hour Fast?

Fasting for 24 hours with empty plate

Having an empty stomach for about 24 hours once a week triggers several processes within the human body. Let’s take a deeper look at them:

Step 1: Blood sugar drop

Fasting for 24 hours decreases your blood sugar levels. During a fast, your body does not have access to glucose, which it normally uses as an energy source. As a result, your body begins converting stored glycogen into glucose for energy. While you’re breaking down glycogen, your blood glucose levels decrease, and the pancreas releases less insulin, a hormone that helps control blood sugar levels. This is a good thing—managing your blood sugar levels can help prevent various chronic diseases and have weight loss benefits. 

Although this process has a positive effect on your health, you may notice that you start to feel hungry, weak, or irritable. These symptoms are normal and should go away as your body adjusts to the fasting state.

To make the most out of this phase, drink water to help flush toxins out of your body and prevent dehydration. Also, try to avoid exercise—it can deplete glycogen stores and lead to your blood sugar dropping even more or result in an energy deficit.

Step 2: Ketosis

Ketosis is a metabolic state your body enters when it runs out of its primary energy source—glucose. This causes your body to burn stored fat to keep its functions running. Your body enters this state after 12 or more hours of fasting.

When you reach this stage, you might notice a few symptoms, including:

These are also normal and will improve with time or simply by taking a sip of a fast-safe drink. But don’t break your fast just yet, as the main benefits of this eating pattern start to appear precisely here.

From this phase, blood sugar control is improved due to the production of ketones. Body fat also starts to be actively reduced as, in the state of ketosis, the body burns even more body fat as an energy source.

To get the most out of this stage, stay hydrated and eat well-balanced food during your eating window. You can also use a ketone meter or test strips to determine if you’re in ketosis and to ensure your ketone levels are within a healthy range.

Just remember to be patient—reaching the state of ketosis takes time, and it’s a rough point in the fasting window to get used to. The process is different for every person, but the key to success is the same for everyone—giving your body time to adapt.

Step 3: Autophagy

Autophagy is a cellular recycling process in which the body repurposes usable bits and pieces of old and damaged cell parts into new, usable ones. It’s a quality control process for your cells, and is essential for maintaining the health of your tissues. 

Autophagy can be triggered by several factors, including intermittent fasting.

During fasting, there are no regular nutrients and energy sources from meals and stored glycogen, so your body can experience metabolic stress and activate the autophagy phase. 

You might notice a few symptoms during this phase, including:

  • Suppressed appetite: This can be a result of increased glucagon levels or decreased insulin levels.
  • Bad breath: This can indicate that your body has reached ketosis, ultimately leading to autophagy.
  • Weakness: Low blood sugar can lead to fatigue, but your energy levels should increase when your body adjusts to the fast.

Physical exercise can help you get the most out of the autophagy phase by inducing autophagy and enhancing its health benefits. As a plus, staying hydrated can maintain your body’s health and function, boosting the effects of autophagy.

Is 24-Hour Fast Good for Weight Loss?

Some research suggests that fasting for up to 24 hours can result in a metabolic shift, leading your body into a fat-burning mode where it will burn stored fats as an energy source instead of glucose. This change, consequently, leads to weight and fat loss.

Fasting may be a more effective calorie restriction method than other diets that require constantly counting and restricting your every meal—in fact, according to a study, intermittent fasting can help you lose 3–8% of your body weight in 3-24 weeks.

Depending on the individual, it’s possible to lose up to 1.65 pounds per week and see a 4–7% waist circumference reduction in the same period. To put this into context, a regular healthy weight loss pace is 1 to 2 pounds a week. Therefore, fasting for 24 hours once a week is a healthy way to achieve weight loss or reduce body fat.

What Are the Benefits of a 24-Hour Fast?

We have already spoken about weight loss as one of the benefits of 24-hour fasting. Let’s learn about other positives this eating pattern can bring to your body:

Can Promote Brain Health

One commonly known benefit of fasting is that it can prompt a metabolic switch in the body. “Switching your metabolism” refers to the usage of ketones as fuel during fasting phases and the return to using glucose after eating a meal. This switch occurs around 12 to 36 hours after the fasting period begins, and it initiates a biochemical cycle that increases the brain’s endurance and efficiency while boosting its support system.

In short, it is known that intermittent fasting can improve cognitive function in both animals and humans by promoting neuroplasticity and long-term potentiation (LTP). This is excellent news, especially for those who care about the long-term health of their brains, as it could help prevent Alzheimer’s, Parkinson’s, and other diseases later in life.

May Improve Cardiovascular Health

The cardiovascular system, which includes the heart and blood vessels, is essential to overall health—it circulates blood throughout the body and delivers oxygen and nutrients to cells and tissues.

There is some evidence that intermittent and 24-hour fasting can be beneficial for crucial areas of the body. In fact, one study reveals that fasting positively impacts several cardiovascular diseases and risk factors, including diabetes, obesity, hypertension, and dyslipidemia, coronary artery disease. Fasting may also help reduce the risk of heart disease.

A 24-hour fast can lower blood pressure and improve cholesterol levels, hence increasing the levels of “good” cholesterol (HDL) and decreasing levels of “bad” cholesterol (LDL).

May Promote Gut Health

According to one study, time-restricted eating may increase circadian gene transcription by activating sirtuin-1, a protein that regulates various cellular processes. This effect may be related to an increase in gut microbiome richness.

The gut microbiome refers to bacteria and other microorganisms that live in the gastrointestinal tract. Their health, or your gut’s health, is essential for immune system support, infection prevention, and proper digestion.

Intermittent fasting or a 24-hour fast can lead to an increased number of beneficial bacteria in the gut microbiome. In addition, fasting allows the gut and digestive system to rest from the constant process of digesting food.

May Improve Insulin Sensitivity and Blood Sugar Control

Insulin sensitivity refers to the body’s ability to respond to insulin and use it to regulate blood sugar levels. Improved insulin sensitivity can help prevent or manage health conditions such as type 2 diabetes, metabolic syndrome, and heart disease.

One scientific research revealed that people who follow an intermittent fasting routine experience a decrease in blood glucose as well as insulin levels. Therefore, fasting 24 hours once a week may be an effective way to improve glucose metabolism, blood sugar control, and insulin resistance.

Another study found that fasting can effectively lower insulin and blood sugar levels, reduce insulin resistance, and decrease leptin levels.

May Reduce Inflammation

Chronic inflammation can lead to various health problems and chronic diseases. Luckily, several human and animal studies reveal that intermittent fasting can limit this process.

One of the many health benefits of the 24-hour fast is that it reduces inflammation by promoting the generation of adenosine, a signaling molecule with anti-inflammatory effects. In addition, intermittent fasting has been shown to decrease the production of cytokines, which are pro-inflammatory proteins. 

Reducing the production of these substances—through fasting, for example—can have anti-inflammatory effects.

How to Prepare for a 24-Hour Fast

Ready to give the 24-hour fast a try? Here are some preparation ideas to help you complete this long fasting window.

Eat nutritious meals before the fasting window

Eating healthy and nutritious meals throughout your non-fasting days will help you stick with more extended periods of fasting, so eat a well-balanced meal before starting your fast. The ideal pre-fasting meal should include a mix of healthy fats, proteins, and carbohydrates.

And don’t overeat! As tempting as it may sound, overeating can lead to discomfort, making fasting more difficult.

To learn which foods are best to eat before a fast, keep a log of your meals and consider using an intermittent fasting app. Programs like DoFasting are specifically developed to make your fasting experience as smooth and straightforward as possible.

Prepare your environment to reduce triggers

It can be more challenging to enter a state of starvation and stay motivated if your kitchen is stocked with junk food or if you have plans to meet a friend at a restaurant. To increase your chances of success, it is crucial to remove tempting snacks and junk food from your home and choose the right time for your fast.

It may be helpful to stay at home and avoid going to restaurants or cafes, even for a zero-calorie drink—remember that even a small meal can break your fast.

Planning ahead and being mindful of your surroundings can help you stay on track and avoid temptation during your fast.

Avoid strenuous exercise

There are a few reasons why you may want to avoid overexercising during a 24-hour fast:

  • Lower energy levels: During a fast, the body’s energy levels may be lower than usual. As a result, engaging in strenuous exercise before a 24-hour fast may further reduce energy levels.
  • Depletion of muscle glycogen stores: Exercise can deplete muscle glycogen stores, which are the body’s primary energy source during exercise. 
  • Increased hunger: Strenuous exercise can also cause you to burn more calories, which may increase hunger levels.

Keep in mind that it is still okay to engage in light to moderate exercise, such as walking, swimming, or stretching during a 24-hour fast. In fact, exercising can get you into ketosis more quickly. Just don’t overdo it!

Stay hydrated

Proper hydration is vital for overall well-being, as it ensures that you get all the benefits of a 24-hour fast. Being adequately hydrated before going without food can help prevent dehydration and its associated symptoms, such as headache, dizziness, thirst, fatigue, or other health complications.

The recommended daily amount of water depends on your gender—men are recommended to drink around 13 cups of water each day, while it is suggested that women drink 9 cups.

An intermittent fasting app can be a helpful tool for tracking your water intake—simply add each cup of water you drink to the app to see how much water you have consumed and how much you still need to drink that day. An easy-to-use water tracker can make staying hydrated and reaching your health goals easier.

Watch your electrolyte intake

Electrolytes are minerals essential for proper bodily function. They assist in regulating nerve and muscle function, pH balance, and hydration. Because your body is deprived of foods throughout your 24-hour fast, it’s critical to monitor your electrolyte intake following the fast.

If your body lacks electrolytes, you might feel weak and experience muscle cramps and fatigue. To ensure you get enough of these minerals, include electrolyte-rich foods in your diet. These can be avocados, potatoes, bananas, and other fruits and vegetables. 

What Should You Eat After a 24-Hour Fast?

When you resume eating after a 24-hour fast, your glucose levels will increase, and (unless you are following a ketogenic diet) your body will return to using carbohydrates as an energy source. Therefore, it is vital to break your fast with the right types of foods.

Eating foods that are hard to digest after a fast can lead to bloating or discomfort. To avoid this, choose nutrient-dense, cooked foods that contain protein and healthy fats and are low in sugar and carbs. These foods can help provide sustained energy and support the body’s recovery after a fast. Avoid junk foods and processed foods.

Some examples of foods you can eat after your fasts are:

  • Eggs
  • Avocados
  • Cooked vegetables
  • Unsweetened yogurt
  • Soups that contain tofu, lentils, or pasta
  • Smoothies

And one last tip: try to be mindful and avoid overeating—you will feel starving after such a prolonged fast, but it is essential to eat a small amount of food when breaking your fast to help your digestive system restart after such a long break.

Side Effects and Risks: Is 24-Hour Fast for You?

As with most changes in habits, fasting has some risks. Here are the possible side effects you may encounter during your 24-hour fast:

  • Hunger: This is the most common side effect of intermittent fasting. The feeling should decrease as your body adapts to your fasting routine.
  • Digestive issues: You might experience constipation, bloating, nausea or diarrhea.
  • Headaches: You might experience mild or moderate headaches throughout your fasting period, but they should go away once your body adapts.
  • Irritability: Low blood sugar might cause you to feel irritated.
  • Low energy: This might be caused by low blood sugar levels.
  • Bad breath: This can be caused by the rise of acetone in the breath.
  • Malnutrition: Not getting enough nutrients in your eating window can lead to malnutrition.

Also, there are certain groups of people who should avoid the 24-hour fast:

  • Pregnant or breastfeeding women: Pregnancy and breastfeeding require unique nutritional needs that may not be met during a fast.
  • Children or teens: Children and teenagers have higher energy and nutritional needs and may not be able to fast safely for 24 hours.
  • People with immunodeficiencies: Fasting may weaken the immune system even further in people with immunodeficiencies.
  • People with eating disorders: Fasting may trigger their symptoms.
  • People with dementia: Those with dementia have unique needs and may have difficulty following a 24-hour fast.
  • People with a history of traumatic brain injury: These people have a higher risk of experiencing adverse effects.

It is essential to consult with a medical professional before starting a 24-hour fast to determine if it is safe for you.

Key Takeaways

A 24-hour fast is a form of intermittent fasting in which you do not eat for a full day once a week. During this time, your body goes through a blood sugar drop, ketosis, and autophagy, and begins to burn fat for energy.

There are several potential benefits to a 24-hour fast, including improved brain health, cardiovascular health, gut health, reduced inflammation, and improved insulin sensitivity. It can also promote weight loss. However, it is crucial to be aware of potential adverse side effects and to take steps to minimize them.

To ensure a successful fast, eat nutritious meals, avoid strenuous exercise, and stay hydrated. Consider consulting with a medical professional before starting a 24-hour fast.


1. How often should you do the 24-hour fast?

Ideally, you should fast once or twice a week.

2. Is it safe?

Generally, a 24-hour fast is considered to be safe. However, you should consult a medical professional as it can have specific adverse effects.

3. What are the benefits of a 24-hour fast?

Intermittent fasting can have a lot of different health benefits. A 24-hour fast can help you improve your cardiovascular health, gut health, and insulin sensitivity; reduce inflammation; and help you lose weight.

At ketogenic.com, we are committed to supporting, inspiring, and educating people on the benefits of living a ketogenic lifestyle. We do this by bringing together the top researchers, practitioners, and thought-leaders who provide resources, experience, and awareness associated around the Ketogenic diet. Utilizing the latest cutting-edge research along with practical experience, the team at ketogenic.com aims to foster awareness, understanding, and connectedness in helping others optimize their life on a ketogenic diet.


  1. Monique says:

    I hope it works. I need to lose a lot of weight

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