If you’re wondering whether a 12-hour fast or a 16-hour fast is better for you to achieve your health goals, you’re at the right place.
This post will share the differences between the two and let you decide based on your lifestyle and needs.
First, you should consult a licensed medical physician before jumping into intermittent fasting. IF isn’t for everyone; therefore, it’s something to discuss with a licensed professional.
The purpose of this post is to give you a simplified version of the differences between 12 hours and 16 hours of fasting; it is not to provide any professional/medical advice.
Jump to:
- Is It Better to Fast for 12 or 16 Hours?
- Is 12 Hour Intermittent Fasting Enough?
- Benefits of 12 hour Fasting
- Benefits of 16 Hour Fasting
- Benefits Comparison Chart
- How Often Can You do 12 Hour Fasting vs 16 Hour Fasting?
- What Happens When You Don’t Eat for 12 Hours?
- What Happens When You Fast for 16 Hours
- Choose The Best Intermittent Fasting Schedule for You
Is It Better to Fast for 12 or 16 Hours?
The easiest way to get started with intermittent fasting is by doing a 12-hour fast and increasing your fasting time to 16 hours as you get used to it.
There are 12 hour intermittent fasting benefits you can feel in just a few days, such as more mental clarity and focus, cellular repair, and jumpstarting your weight loss journey.
While studies show that a minimum of a 12-hour fast is enough to help you get the benefits, the 16/8 intermittent fasting method is by far the most popular out there.
If your goal is weight loss, both a 12 hour and a 16 hour fast are beneficial. If your goal is to heal damaged cells, and cellular repair, you’ll need to fast for 14 to 16 hours to enter this stage of intermittent fasting.
Is 12 Hour Intermittent Fasting Enough?
This is the million-dollar question among beginners and long-term intermittent fasting practitioners.
While research shows that 12 hours is enough, those who practice intermittent fasting and follow a keto diet swear by the 16-hour fasting window to help them stay in ketosis.
That said, many people do intermittent fasting without keto to achieve their health goals.
Benefits of 12 hour Fasting
The benefits of 12 hour fasting include weight loss, improved digestion, improved sleep, increased mental health and clarity, and reduced insulin resistance.
One reason the 12-hour fast is great to start intermittent fasting is that most people spend 7 to 8 of those hours sleeping, and therefore, getting to 12 hours without eating requires little effort or struggle.
Benefits of 16 Hour Fasting
The benefits of a 16-hour fasting schedule are the same as a 12-hour fasting. They include weight loss, aid in the cellular repair process, improved sleep, improved digestion, increased mental health and clarity, and reduced insulin resistance.
The main difference is that after 14 to 16 hours, your body can enter the autophagy phase, where it begins to repair itself at a cellular level.
If you’re following a keto diet while fasting, the 16 hour fast tends to help many people stay in ketosis by providing the body an extra 4 hours to not produce any insulin from the foods consumed when breaking the fast.
Benefits Comparison Chart
| Benefit | 12 hour fast | 16 hour fast |
|---|---|---|
| Improved sleep | yes | yes |
| Improved digestion | yes | yes |
| Improved mental focus | yes | yes |
| Aids with weight loss | yes | yes |
| Autophagy (cellular repair) | no | yes |
| Overall health | yes | yes |
| Insulin regulation | some | yes |
How Often Can You do 12 Hour Fasting vs 16 Hour Fasting?
Most people practice intermittent fasting regularly. It is also possible to alternate between fasting 12 hours on some days and 16 hours on other days; it just depends on your lifestyle and schedule.
There’s no rule on how often one should fast and not fast, that said, pregnant or nursing women should not practice intermittent fasting.
What Happens When You Don’t Eat for 12 Hours?
With a 12-hour fast, when you omit to eat, your body can focus on other processes other than digestion.
This means that your body can begin to reduce inflammation, convert its fat stores into energy, get a more restful sleep, release ketones into the bloodstream, wake up more alert and have more focused energy in the morning, and more.
What Happens When You Fast for 16 Hours
A 16 hour fast is considered the standard for people who practice intermittent fasting long-term.
A lot of people express that there is a lot of freedom that comes with fasting for 16 hours since fasting creates a limited eating window in which to eat all your meals.
The biggest benefit of fasting for 16 hours is entering the autophagy stage, where the body self-heals (also referred to as cellular repair) and it begins to reduce inflammation, boost its immune system, and age healthily.
Studies also show that it might take up to four days for the body to enter this self-healing stage, which is why I recommend that you start with a 12 hour fast and work your way up to a 16 hour fast.
Contrary to popular belief, intermittent fasting is not just skipping breakfast so you’ll need to think about when and what to eat if you have a busy lifestyle.
In addition, having an intermittent fasting meal plan can be highly beneficial if you’re just starting out. Learn more in the video below.
Choose The Best Intermittent Fasting Schedule for You
The best intermittent fasting schedule is one you can maintain without feeling deprived of food.
For some people, stopping their food intake at 7 pm and waiting until 11 am or noon to break their fast is an easy thing to do. For others, especially those who exercise in the morning, holding out for an extra 4 hours can be tough.
If you’re just starting intermittent fasting, consider downloading this full eBook and meal plan.
Intermittent Fasting 101
Recipes, a meal plan, plus everything you need to jumpstart your intermittent fasting journey!
John says
Hi. Great and super helpful information. thank you
Mary Ann says
Hello! I enjoy a 16:8 eating schedule daily. If I feel hunger pangs during my fasting period, I use deep breathing exercises to make them stop. It works!
Donna says
Thank you.
Joanell Serra says
The study I just read said that studies show the body doesn’t really don’t achieve until 48-72 hours (which I cannot pull off.) Are you pulling data from studies that say otherwise? I would be doing the fasting for health, not weight loss. 12 hours is easy enough. 16 is harder, so I am trying to find accurate data. Thanks!
Laura Fuentes says
I believe that what you are referring to is ketosis, which is a state where your body uses fat for fuel. To achieve ketosis, it will take your body 48-72 hours to adapt. This is achieved through a low-carb diet and fasting; not intermittent fasting alone. You can benefit from intermittent fasting by doing a 12-16h fast, this is very different than ketosis.
Peter says
Ive been doing the average of 14 to 18 hour a day fast and after one year two months of doing this steady without error , I lost 65lbs and got my life back ,when now I can do the things that were unthinkable before at 275 lbs. now 210 . I’ll share my secret since I have much experience in this , I tried all the different times of the day to eat to give the best results ,and the hardest is first eat between 6 am and 12 noon. the second best and a lot easier and the one I recommend for a life time do ,is start at 8am to 2pm afternoon and then for the rest of the day only water or black coffee with no sugar or milk ect.. after you body looses the excess weight according to your weight , even if you fast you will no-longer loose weight at a higher pace ,but continue to stay at you new healthy weight ,but one good news you can cheat and eat the whole day if you want only for days in a month !!! and nothing will happen to your weight . I’m am now at the stage of trying to loose another 20 lbs ,but its now slower and harder than before , even at the same pace and giving myself till Christmas to do so . I even gained 5 lbs back going to a 12 hr fast , so if you don’t want to gain some weight back it better that you pick the time table you want and stick to it for the best results… this will save your life ,and my gift to all of you ,cause I suffered so much in reaching and now finally used to this system. If your not strong of mind and will ,I’ll tell you now ,you won’t succeed . so at least do the 12 hr. fast ,its easy eat from 6am to 6pm only and you will get a decent benifit from it ,but it will take 2 years instead of 1 to get the same benifit like mine as an example !! good luck
Avi says
Thank you, Peter, for the obvious time and effort you put into your info sharing. I’m into the 3rd month of a 12-13 hr fasting period. I lost a quick 3-4 lbs which was not in the direction I wanted, being a thin, small framed senior. So I’m monkeying around with my diet. Right now I’m experimenting with high fat (from MCT oil only source of the fat), about 20 grams per meal of lean protein, and a 15 gram per meal of a mickey moused version riced cauliflower (quenoa mixed together with riced cauliflower in a mixture of 4 cauliflower/1 quenoa. I’m learning to reach for a cup of water to drink instead of food (to which I’m addicted).
God bless