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Home arrow Nutrition arrow Intermittent Fasting arrow The 12-Hour Fast: What Is It, and How Does It Work?

The 12-Hour Fast: What Is It, and How Does It Work?

Written by Edibel Quintero, RD
Fact checked by Rosmy Barrios, MD
Last update: October 17, 2023
8 min read 2034 Views 0 Comments
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The 12-hour fast is a method of intermittent fasting thought to make weight loss easier. See our article to find out how this fasting method could help you lose weight today.

12 hour fast

Intermittent fasting is a popular dieting method many people have had success with when trying to lose weight. It comes with a range of health benefits and can help you reduce your body’s fat stores.

The 12-hour fast is one of the least challenging forms of intermittent fasting and involves a fasting period of 12 hours.

This fasting method helps you reduce your calorie intake and may push your body into the metabolic state of ketosis, which is good for burning fat.

In this article, we’re going to look at the 12-hour fast, what it is, how it works to help you reduce your body weight, and the benefits of this intermittent fasting plan, among other things.

Keep reading now to learn more.

How to Do the 12-Hour Fast

A 12-hour fast involves fasting for a 12-hour period. Usually, people begin their fasting period at 7 PM after their evening meal and then break the fast at 7 AM the next morning.

The 12-hour fast allows the majority of the fasting window to be during sleeping hours, which can make it easier for those who are new to intermittent fasting.

Research suggests that fasting for a period of more than 10 hours can push the body into the metabolic state of ketosis. This state forces the body to burn fat cells for fuel rather than blood glucose, helping you lose weight.

Along with the benefits of the fasting period, the 12-hour fast shortens your eating window, forcing you to restrict your daily caloric intake and helping you eat at a calorie deficit, which is essential for weight loss.

12-Hour Fast – Is It Enough?

Research suggests that fasting for 12 hours is enough time to allow your body to move into the state of ketosis – which is the aim of all intermittent fasting plans.

A 12-hour fast will also ensure you can eat fewer calories per day due to a shortened eating window, which is particularly useful if you are prone to midnight snacking.

While a 12-hour fast is long enough to move your body into ketosis and ensure you begin burning fat, some may find that the 12-hour eating window does not cause a calorie restriction as it still allows time for three meals a day.

If you try the 12-hour fast and see fewer results than you’d like, why not try a more challenging fasting style, like the 14:10 method, or the 18:6?

How many hours without food is considered fasting?

A fasted state is achieved when you have not eaten or drunk anything but water and other calorie-free drinks for 10–12 hours.

A fasting period is characterized by the body moving from burning blood glucose to breaking down stored fat reserves into fatty acids called ketones for fuel instead.

There are many methods of intermittent fasting, and you can choose the one that suits your needs best. Try the 12:12 regimen or opt for the 16:8 fast.

How many calories do you burn fasting for 12 hours?

There is no set number of calories that are burned during a 12-hour fast, as the number of calories we burn depends upon the weight, age, and sex of the individual.

With a 12-hour fast, most of the fasting hours occur during sleep. The body burns calories during sleep as it uses energy to repair and reset the body, meaning your body is getting through calories even when you are sedentary.

Your individual metabolism will also have an impact on how many calories you burn during a fast. Your metabolism is the process through which the body converts food into fuel.

It is thought that fasting may increase your metabolic rate, meaning that you will burn more of the energy stored in your body and, therefore, more calories the longer you follow a pattern of intermittent fasting.

Can You Lose Weight With a 12-Hour Fast?

Intermittent fasting has been shown to have positive effects on weight loss. A 12-hour fast pushes your body into a fasting state where it begins burning body fat for fuel rather than blood sugar, making it easier to lose weight.

In addition to the metabolic switch that a 12-hour fast can force, eating for a shorter period of time has been shown to be successful in helping restrict calories.

If you eat breakfast at 7 AM and then eat your last meal at 7 PM, you have a shorter amount of time to eat and will, therefore, eat less than you would if you continued snacking until 10 PM.

It is important that during the eating period, you follow a balanced diet and eat nutrient-dense foods as this increases your likelihood of losing weight while intermittent fasting.

What Happens to Your Body When You Fast for 12 Hours?

During a 12-hour fasting window, the body switches from burning blood glucose for energy to burning fat as the body undergoes a metabolic switching to the state of ketosis.

As the levels of glucose decrease in your blood, the liver begins fat oxidation, which turns stored body fat into fatty acids called ketones. These ketones are then burned for fuel.

Burning fat for fuel helps people reduce their body weight, as well as reduce their risk of a range of chronic illnesses, like heart disease, reducing cholesterol levels, regulating blood pressure, and improving blood sugar levels.

Benefits of 12-Hour Intermittent Fasting

The intermittent fasting diet is popular for its use in adult weight loss, but it also comes with other major health benefits. Below, we have summarized the health benefits of intermittent fasting.

#1 Weight loss and weight management

Fasting for more than 10–12 hours pushes the body into the metabolic state of ketosis, where body fat is burned for fuel rather than blood sugar. This helps reduce body weight and the amount of stored fat in the body.

Intermittent fasting also creates much shorter eating periods, making it more difficult to overeat. With fewer hours to actually eat, you are unlikely to eat more than the recommended number of calories each day, creating a calorie deficit that is essential for weight loss.

It may also be useful for people who have tried other kinds of diets with little success. This is because intermittent fasting allows you to continue to eat the things you like but restricts the time you can eat them.

If you’re considering using intermittent fasting as a method of weight loss, check out the DoFasting app for tips and tricks on maintaining this diet, as well as recipes that are intermittent fasting-friendly.

The app also offers motivation boosts and progress tracking to help you stay inspired as you fast.

#2 More energy

Intermittent fasting is thought to improve energy levels.

It is thought that with an increase in your metabolic rate, the body increases its energy expenditure, too, meaning your body becomes better at its energy usage.

Intermittent fasting improves energy levels because it allows your cells time to rest and gives your body a period where it doesn’t have to produce insulin and other hormones in response to an increase in blood glucose.

#3 Reduced inflammation

Inflammation in the body can cause many chronic illnesses and lead to you feeling ill, weak, and tired. Intermittent fasting decreases inflammation in the body.

Though inflammation is the body’s natural response to injury, chronic inflammation is known to be detrimental to health. Reducing this inflammation is thought to be beneficial for both brain and heart health, lowering your risk of neurodegenerative diseases and heart disease.

In addition, intermittent fasting may be useful in defending the body against oxidative stress – another cause of many chronic illnesses as well as the signs of aging.

#4 Better discipline

Intermittent fasting is a really good way to get some discipline when it comes to weight management.

By restricting the time you can eat, you eat fewer calories and train your body to get used to consuming less. You may also be able to stop yourself from extra snacking, especially around bedtime.

In addition, due to the long periods of fasting and the danger of vitamin deficiencies, you will need to ensure you’re eating foods packed with nutrients helping you to get a healthier and more balanced diet.

How to Maintain a 12-Hour Fast

Now that you understand all of the benefits of the 12-hour intermittent fasting method, you’ll probably want to know how to maintain this kind of diet. Below, we’ve summarized our top tips for staying on track.

#1 Have a schedule

Sticking to the same schedule of eating and fasting can help you to maintain your fast more easily. If you know what you’re eating and when, you’re less likely to go off track, eat the wrong things, and give up.

Having a schedule will also make it easier when it comes to planning social events, work deadlines, and anything else that could be impacted by fasting for long periods.

#2 Eat nutritious food

Eating nutritious food is essential for maintaining health during the intermittent fasting diet. You need to make sure you eat enough nutrients during the eating periods to not suffer hunger pains or low blood sugar when you are fasting.

Due to a shortened feeding window, deficiencies are a danger when trying intermittent fasting. Ensure you choose nutrient-dense food options, like whole foods, fruit, and vegetables. You should try to eat from all of the food groups and prioritize staying hydrated during intermittent fast periods.

#3 Let your body adapt

When you first begin intermittent fasting, you may find it difficult to refrain from eating for such a long period of time. It takes time for your body to get used to the fasting period, and you may suffer some negative side effects in the early stages.

These side effects could include nausea, dizziness, headaches, and hunger pangs but are likely to get better the longer you follow an intermittent fasting diet.

Once your body has adapted to the 12-hour fast, you may find you want to try more challenging intermittent fasting methods, such as the 16:8 fast or the Warrior diet.

As you begin to try more challenging time-restricted feeding methods, you will also need to learn to ease your body out of long fasts by slowly reintroducing solid foods and choosing meals that are gentle on your digestive system.

A Word From Our Nutritionist

The 12-hour fast means refraining from consuming any calories for 12 hours each day. Most people choose to fast from around 7 PM, after eating their evening meal, until they eat their breakfast at around 7 AM.

Research has shown that fasting for at least 10–12 hours can help the body burn fat for fuel rather than blood glucose, which can help you lose weight and reduce the amount of fat in your body.

Reducing fat can have lots of benefits besides weight loss, like reducing your risk of certain cardiovascular diseases and helping regulate blood pressure.

Intermittent fasting is also a good way of decreasing the number of calories you consume, helping you eat at a calorie deficit, and promoting weight loss.

This method of time-restricted eating has been shown to help people reduce their body weight and improve overall health, with added benefits including improved energy and mental clarity, reduced inflammation, and better discipline.


The 12-hour fast is a method of intermittent fasting that has been shown to help people lose weight and reduce body fat.

It involves fasting for 12 hours a day and can help restrict your daily calorie intake and improve your overall health.

If you’re thinking of starting an intermittent fasting diet plan, you can check out the DoFasting app for tips, guidance, and motivation, along with thousands of recipes and tailored workouts.

Written by Edibel Quintero, RD
Edibel Quintero is a medical doctor who graduated in 2013 from the University of Zulia and has been working in her profession since then. She specializes in obesity and nutrition, physical rehabilitation, sports massage and post-operative rehabilitation. Edibel’s goal is to help people live healthier lives by educating them about food, exercise, mental wellness and other lifestyle choices that can improve their quality of life.
The article was fact checked by Rosmy Barrios, MD
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Written by Edibel Quintero, RD
Fact checked by Rosmy Barrios, MD
Last update: October 17, 2023
8 min read 2034 Views 0 Comments

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