12 Hour Fast Benefits + How To Fast Properly And Effectively For 12 Hours

One of the hallmarks of most effective weight loss diets is that they are generally somewhat restrictive, at least in terms of what you can and cannot eat, how much you can eat, or potentially when you can and cannot eat if you are following an intermittent fasting diet.

However, fasting for 12 hours per day still gives you 12 hours of unrestricted eating to space out and time your nutrient intake. This can help you feel less restricted while still giving some structure to your caloric intake over the course of the day.

But, are there 12 hour fast benefits? What are the 12 hour fasting benefits? Are the 12 hour fast benefits enough to support weight loss and improve health? Let’s find out!

In this guide, we will cover: 

  • What Is a 12 Hour Fast?
  • What Are the 12 Hour Fast Benefits?

Let’s dive in! 

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What Is a 12 Hour Fast?

Before we discuss the benefits of fasting for 12 hours, let’s briefly discuss what a 12 hour fasting diet looks like and how to do a daily 12 hour fast.

A 12 hour fast is generally categorized as a time-restricted intermittent fasting diet called the 12:12 intermittent fasting diet schedule or 12/12 intermittent fasting.

The 12/12 intermittent fasting diet means that there is a 12-hour fast every day and a 12-hour eating window every day, but you can schedule these windows of time any way that you choose. 

For example, you might begin the 12 hour fast at 8 PM, and then you will have your first meal the next day at 8 AM.

This means that your eating hours are from 8 AM to 8 PM, and you do your 12 hour fast from 8 PM every night overnight until 8 AM when you have your first meal.

For most people, unlike a more aggressive, prolonged fasting period such as a 24 hour water fast or 36 hour water fast, a 12 hour fast is part of a consistent, daily, habitual diet rather than a once-a-week or occasional fasting challenge.

This means that every day of the week unless you have a “cheat day” built into your intermittent fasting diet routine, you would split your 24 hour day into a 12 hour fast and a 12 hour period where you must do all of your eating and drinking of caloric foods and beverages.

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During the 12 hour fast, you are permitted and encouraged to drink as much water and noncaloric drinks as you wish. 

Aside from plain water, you can have carbonated water or seltzer, herbal tea or caffeinated tea, or black coffee without any sweetener or cream while fasting.

Then, when the 12 hour fasting window is over, you are allowed to eat and drink anything that you want.

Of course, the focus should be on nutrient-dense, healthy foods from a range of food groups, such as vegetables, fruits, eggs, low-fat dairy products, lean proteins, legumes, whole grains, nuts, and seeds. 

Depending on your dietary preferences, weight loss goals, caloric needs, and food preferences, you may also choose to combine the 12/12 intermittent fasting diet with other weight loss diets or lifestyle diets such as the keto diet, the Paleo diet, the vegan diet or other plant-based diets, or a low sodium diet.

Ultimately, the 12:12 intermittent fasting diet, like all intermittent fasting diets, it’s not stipulated what you can and cannot eat during your eating window; it’s just that you have a restricted time to eat, so when you eat or have to fast is what is governed.

What Are the 12 Hour Fast Benefits?

There are numerous potential health benefits of fasting 12 hours as well as logistical benefits. Here are some of the 12 hour fast benefits:

A person eating toast.

#1: Flexibility

As mentioned, there is a lot of flexibility with a 12 hour fast. You can choose when you want to fast and when you want to eat, and you can also choose what you want to eat. 

This flexibility can make the 12/12 intermittent fasting diet sustainable in the long term and can improve adherence so that you can stick with your weight loss and health goals.

#2: Beginner Friendly

Intermittent fasting diets are a popular approach to weight loss and health, but some are pretty restrictive due to the long fasting period every day.

A 12 hour fast is essentially what most people experience every day with the overnight fast as they sleep. 

Depending on the exact timing of your last meal or snack before bed and your breakfast or first caloric intake in the morning, trying a 12 hour fast may not necessitate all that much variation or deliberate restriction of food intake beyond what you are already naturally doing. 

For example, if you eat dinner at 7 PM and then do not have a bedtime snack, you just have to wait until 7 AM to have breakfast and/or caloric beverages like coffee with added cream and sugar or tea with milk in the morning.

This can make a 12 hour daily fast a good stepping stone or beginner-friendly option for people interested in intermittent fasting before progressing to more aggressive intermittent fasting schedules.

Another 12 hour fasting benefit is that the “side effects” of long fasts, like feelings of hunger, headaches, dizziness, irritability, and low energy, are minimized with this more moderate approach.

Plus, it is easier to fit in your workouts while still feeling well before and afterward because the eating window is long enough.

The word insulin and a stethoscope.

#3: Improved Insulin Sensitivity

Intermittent fasting alters your hormonal profile, which, in turn, can cause numerous potential health benefits. 

For example, intermittent fasting reduces insulin levels, which can reduce the risk of insulin resistance while also supporting fat loss.

Around the 12 hour mark into a fast, your blood sugar levels should be decreased enough that some amount of fat burning starts to take place.

However, much shy of a 12-hour fast duration, your body should still have enough blood glucose and accessible glycogen to use carbohydrates and fat for fuel.

Therefore, the body doesn’t have to do all that much in terms of adapting to a lack of energy intake when you are fasting for less than 12 hours

This does mean that your insulin won’t drop as much as with longer fasting times, but there are still insulin benefits of fasting 12 hours.

The less often you are eating—particularly high-carb foods—the less frequently your insulin levels will rise.

This can potentially reduce the risk of insulin resistance and type 2 diabetes.

A person measuring their waist.

#4: Increased Metabolic Rate

Although prolonged fasting decreases your metabolic rate, studies suggest that short-term restriction of your energy intake can increase your metabolic rate and stimulate lipolysis, or the breakdown of body fat for energy.

#5: Weight Loss

Studies have found that intermittent fasting can support weight loss.

For example, a review of 27 intermittent fasting dietary interventions found that all 27 studies resulted in weight loss of 0.8% to 13.0% of the starting weight with no serious adverse effects. 

Keep in mind that if you are only fasting 12 hours a day, you still have 12 hours to eat, which is long enough to consume a significant number of calories.

If you are seeking 12 hour fast weight loss benefits, you will need to be mindful of your caloric intake and energy expenditure, striving to be in a caloric deficit in order to lose weight fasting 12 hours a day.

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#6: Reduce Oxidative Stress

Studies also suggest that intermittent fasting can also help defend your body from oxidative stress, which is damage due to free radicals and reactive species.

Oxidative stress is associated with cellular aging, premature breakdown of proteins and cellular membranes, and even alterations to DNA.

Therefore, by helping the body fend off oxidative stress, intermittent fasting can help protect against cellular breakdown and can potentially combat aging.

#7: Decrease Inflammation

Additionally, intermittent fasting can reduce inflammation, which contributes to chronic diseases such as obesity, heart disease, and certain cancers.

#8: Reduce the Risk of Diseases

One of the benefits of a 12 hour fast every day is that this pattern of caloric intake may help reduce the risk of various diseases, such as type 2 diabetes, certain cancers, and obesity, primarily due to the decrease in oxidative stress, inflammation, and insulin. 

With more prolonged fasting, there is also an increase in autophagy, which can help reduce the risk of neurodegenerative diseases such as Alzheimer’s disease and may further reduce your risk of the aforementioned conditions.

If you are interested in extending the intermittent fasting hours from the 12/12 intermittent fasting diet, consider progressing to the 16/8 intermittent fasting diet. You can learn more about the benefits of a 16 hour fast here.

A plate with the numbers 16 and 8 on it, utensils, and apple and a clock.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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