12:12 vs. 16:8 intermittent fasting explained by Simple
Which is better?
Cats or dogs?
Peanut butter or jelly?
Ketchup or mustard?
12:12 vs 16:8 intermittent fasting
How 12-hour and 16-hour fasts compare for weight loss and health.
We love a good showdown, and intermittent fasting is full of them. From quick Google searches to long comment threads, people want to know which intermittent fasting schedule actually works best for fat burning, weight loss, metabolic health, and everyday life.
Enter the classic debate: the 12 hour fast vs. 16 hour fast.
Both are popular forms of time restricted eating time restricted eating . Both shape your eating pattern by setting a fasting window and an eating window. And both can support your health and weight loss goals when paired with balanced food choices and an eating plan that fits your life.
But which one helps you lose weight more effectively? And which fasting method supports energy levels, blood sugar balance, and body weight management without feeling like a daily battle?
Peanut butter or jelly?
12:12 or 16:8?
Let’s break down these two heavyweight intermittent fasting intermittent fasting schedules, compare fasting hours, eating windows, and potential health benefits, and help you decide which one makes most sense for your goals.
What is 16:8 intermittent fasting?
The 16:8 intermittent fasting method involves fasting for 16 hours and eating all your meals during an 8-hour window.
This time restricted eating pattern is one of the most popular intermittent fasting schedules because it’s simple to follow and can support weight management, fat burning, and metabolic health.
If you’re new to intermittent fasting, you might be thinking, “16 hours without so much as an apple? Is that even possible?!”
Here’s the good news: a big chunk of that 16 hour fast happens overnight. Then, by skipping breakfast, you can easily complete a 16 hour fast without feeling deprived. Or, if you love breakfast, no worries. Just shift your eating window earlier in the day, finish with an early dinner, and slide straight into your overnight fasting window.
This flexibility makes time restricted feeding manageable, keeps your daily calories in check naturally, and makes 16:8 a powerful method for losing weight and improving health outcomes.
What is 12:12 intermittent fasting?
If a 16-hour fast feels too hard to handle, 12-hour intermittent fasting could be the fix you need.
The 12:12 intermittent fasting method involves fasting for 12 hours and eating during the remaining 12 hours. It’s an ideal intermittent fasting schedule for beginners, as it’s less restrictive and easier to manage.
Many people find the 12-hour fast easier because it includes a significant portion of sleep time. For example, if you break your fast with breakfast at 8 AM and stop eating after dinner at 8 PM, there’s only a few food-free hours when you’re up and awake.
The difference between 16:8 and 12:12 intermittent fasting
The 12:12 intermittent fasting method is often recommended for beginners. Fasting for 12 hours can be easier to manage because much of the fasting occurs during sleep, whereas the longer fasts of 16:8 can feel tougher.
Aside from that obvious difference, there are three clear ways these two fasting schedules differ.
1. When — or if — you hit ketosis
Both 16:8 and 12:12 can put your body in ketosis ketosis (when your body burns fat stores for fuel). However, it’s more likely with 16:8 because of the longer fasting period. Some people don’t enter ketosis on 12:12 simply because the fast is shorter, though other factors like activity levels, carbohydrate intake, and age can play a role.
2. The calorie deficit
One of the best things about intermittent fasting is not having to count calories to lose weight. You naturally eat fewer calories thanks to the shorter eating window. Longer fasting hours usually leads to a greater calorie deficit, as follows.
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12:12: deficit of roughly 200 calories
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16:8: deficit of roughly 300–400 calories
That said, this will vary depending on your diet. To stay full and energized while eating less, focus on eating more nutrient-dense foods, lean protein, whole grains, and healthy fats. To help you do this, check out our guide: what to eat during intermittent fasting!
3. The side effects
Intermittent fasting can have side effects, especially early in your fasting journey. You might experience increased hunger, cravings, grumpy moods, or stronger snacking urges, for instance. Longer fasts tend to intensify these effects. They usually subside as your body adapts, but if side effects persist, check in with your healthcare provider.
12:12 vs 16:8 at a glance
| Feature | 12:12 intermittent fasting | 16:8 intermittent fasting |
|---|---|---|
| Fasting hours | 12 hours | 16 hours |
| Eating window | 12 hours | 8 hours |
| Best for | Beginners, easier lifestyle integration | Those with more intermittent fasting experience |
| Ketosis likelihood | Possible, but less likely | Higher likelihood |
| Calorie deficit | Roughly 200 calories | Roughly 300–400 calories |
| Side effects | Mild hunger or cravings at first | More intense hunger and cravings, at first |
| Autophagy & metabolic benefits | Less likely due to shorter fasts, but still possible | Fasting for 16 hours can activate autophagy signals in the body and increase health benefits |
| Ease of adherence | Generally easier | More challenging, especially initially |
Benefits of 12:12 and 16:8 intermittent fasting
Here’s a brief rundown on how intermittent fasting can support your health.
Weight loss
Weight loss is one of intermittent fasting ‘s best-known benefits. Intermittent fasting can support fat loss and reduce body weight when combined with healthy food choices, a balanced eating plan and regular exercise.
There’s more evidence to support 16:8’s efficacy for weight loss results for those living with overweight and obesity.[1] That said, 12:12 has been shown to lead to weight loss for those living with obesity.[2]
Improved blood glucose control
Frequent fasting can improve the body’s ability to respond to insulin — a hormone that breaks down the carbohydrates we eat — which can help lower the risk of developing type 2 diabetes.[3] However, these benefits may be more likely for those who are overweight or have obesity.
Increased cardiovascular health
Studies have shown that intermittent fasting may help to reduce LDL cholesterol and triglycerides, two common risk factors for cardiovascular disease, though the researchers noted these benefits may not be clinically significant.[4]
There is good evidence, however, to suggest that intermittent fasting can significantly lower systolic blood pressure, which contributes to heart health.[4]
Anti-inflammatory effects
Intermittent fasting may enhance the body’s resistance to oxidative stress. This can help lower inflammation, which can often lead to chronic diseases.[5,6]
Risks of 12:12 and 16:8 intermittent fasting
There are a few risks with intermittent fasting to be aware of.
Dehydration
Fasting can result in dehydration, leading to headaches, fatigue, and feeling groggy. Drink plenty of water or other low-calorie fluids during both your fasting window and eating window. Check out our guide on what you can drink while fasting to keep your drinking choices fresh and interesting.
Disordered eating
For some people, intermittent fasting can trigger disordered eating behaviors, like binging or restricting.[7,8] If you feel that fasting is having a negative impact on your thoughts and feelings, it may not be the safest way for you to lose weight. Stop and speak to your healthcare provider to find a method that better suits your needs.
Weight gain
Sometimes fasting can kick your hunger and cravings into overdrive.
Perhaps you exercised more than usual, didn’t sleep well, or your stressors increased — these factors can all throw your appetite cues off and make it hard to make healthy food choices. Having a meal plan and some enjoyable, nutrient-dense foods ready to eat will make it easier to grab what you need rather than what you’re craving.
Are 12:12 and 16:8 intermittent fasting safe?
For most people, both 12:12 and 16:8 intermittent fasting are safe and can support weight management, fat loss, and overall health.
However, intermittent fasting is not safe for everyone. Certain groups should avoid fasting unless approved by a healthcare provider. This includes people who:
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are under 18 or 80 years or older
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have a Body Mass Index (BMI) below 18.5
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take prescription medications
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have (or are at risk of having) an eating disorder or have a history of one
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have a medical condition
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are extremely active
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are pregnant, breastfeeding, or trying to conceive
If any of these apply to you, do not try any intermittent fasting schedule without guidance from your doctor. Safety and long-term health always come first.
Pros and cons of the 12:12 and the 16:8 intermittent fasting method
| Pros of 12:12 | Cons of 12:12 |
|---|---|
| Flexible and easy to follow | Can increase hunger and cravings |
| Can support weight loss | You may feel irritable or headachy |
| Improves insulin resistance | You may not achieve ketosis |
| Fits easily into daily life | Weight loss potential is limited |
| Includes a significant portion of fasting during sleep | Fasting for 12 hours yields less metabolic health and hormone benefits than fasting for more than 12 hours. |
| Pros of 16:8 | Cons of 16:8 |
|---|---|
| Can support greater weight loss | Longer fasting hours may increase hunger and cravings |
| Fasting for 16 hours can activate autophagy signals in the body. | May feel challenging for beginners |
| Can improve metabolic health and insulin resistance | Shorter eating window may require careful meal planning |
| Supports fat burning and body weight management | — |
How to get started with 12:12 or 16:8 intermittent fasting
If you’re eager to begin your intermittent fasting journey, here are five steps to help you get started.
1. Choose your fasting schedule
In the battle of 12-hour fasting vs. 16-hour fasting, which one fits your goals and lifestyle?
Think about what fits your daily routine, social life, and energy, and how your meal times might align to suit your sleep patterns, work life, and workout schedule.
2. Decide your fasting hours
Will you eat earlier and finish earlier (science suggests this is optimal [9]) or prefer a later eating window? It’s your call. Play around with different timings to see what fits your life and goals.
3. Write a meal plan
Even a few days of well-planned, balanced meals will help you hit a natural calorie restriction and enhance fat burning and weight loss. If you’re doing 12:12, check out our intermittent fasting meal planning how-to guide. And if you’re following 16:8, our 16:8 intermittent fasting 7-day meal plan will give you a head start.
4. Keep your mind occupied
At first, hunger may feel intense. Distract your brain with something engaging: listen to music, meditate, call a friend, do a puzzle, paint, or knit. Being mentally engaged with an activity is a powerful way to keep hunger from derailing your fast.[10]
5. Use smart tools to manage your fasting journey
Use reminders to prompt you to start and end your fasts, and trackers to log your meals, drinks, and workouts. This helps you see patterns, understand what works for your body, and stay consistent — which means faster results.
The Simple app makes this easy, with tools to track your fasting hours, nutrition, movement, and progress, plus personalized insights and coaching to maximize your progress. Take our quiz to get started and find a fasting plan that fits your life!
5 pro tips on how to choose the right intermittent fasting schedule for you
Here are five practical tips to help you find an intermittent fasting schedule that supports your goals, lifestyle, and long-term health.
1. Experiment
Think of intermittent fasting as a fasting practice, not a one-shot decision. Try a schedule, notice how your body responds, and adjust as needed. You won’t know how a fasting window feels until you experience it for yourself.
2. Start small
Beginning with a shorter fasting period gives your body time to adapt. Many people start with 12:12 and then gradually reduce their eating window to 14:10 or 16:8 if things feel manageable.
3. Make fasting fit your life
Your eating pattern should support your life, not complicate it.
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If life is busy and regularly chews up your time like termites on a log cabin, a longer eating window gives you flexibility. Schedules like 12:12 or 14:10 can support weight management without draining your energy levels.
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If your days are calmer and you enjoy planning meals, longer fasting practices like 16:8 intermittent fasting or 18:6 could be your ideal routine.
4. Give yourself time to adapt
It’s normal for fasting to feel awkward at first. Hunger may spike, cravings may pop up, and you might accidentally break your fast now and then. That’s part of the learning curve. Give yourself time to adjust. If a schedule still feels miserable after a few weeks, switch it up.
5. Stay flexible
The intermittent fasting schedule that works today may not work next month, especially if your job, fitness routine, or stress levels change. Stay flexible and let your fasting practice evolve as your needs shift.
Some intermittent fasting schedules are best left alone
One final tip from the Simple team: stick with time-restricted-eating (TRE) options like 12:12, 14:10, 16:8, or 18:6 intermittent fasting. These fasting practices are kinder to your body, safe, and plenty effective for most.
If you have your doctor’s approval, the 5:2 diet and alternate-day fasting could be options. But it’s best to avoid more extreme methods like dry fasting, the Warrior diet, and OMAD, as they tend to carry higher risks without additional benefits.
Frequently asked questions about 12:12 vs. 16:8 intermittent fasting
Is a 12-hour fast as good as a 16-hour fast?
For weight loss, a 12-hour fast isn’t quite as effective as a 16-hour fast. Studies suggest that longer fasting days can help improve insulin resistance, increase fat burning, and reduce stored fat more effectively.
Is 12:12 intermittent fasting as effective as 16:8 intermittent fasting?
It depends on your goals. 16 hour fasts tend to lead to greater weight loss and a bigger change in waist circumference compared to 12:12.
However, 12:12 fasting can still help you lose weight and is a great way to establish a sustainable fasting lifestyle. Your results also depend on how many calories you eat, your diet plan, your activity level, and other lifestyle factors.[11]
What are the best hours for 16:8 fasting?
The best hours for 16:8 fasting are the hours that work best for you. For some, skipping breakfast is the key; for others, it’s skipping dinner. The key is to stick to your chosen eating window and follow a healthy diet plan on non-fast days.
What should I eat after a 16-hour fast?
After a 16-hour fast, focus on eating:
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a meal which helps you eat enough daily calories for your needs
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nutrient-dense foods that release energy slowly to prevent blood sugar spikes
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a combination of lean proteins, healthy fats, whole grains, fruits or veggies, and calcium-rich foods
Do you burn fat after 12 hours of fasting?
Whether you burn fat after 12 hours of fasting is hard to say, but it’s certainly possible.
Results vary. Not everyone enters ketosis after a 12-hour fast, and those who do typically start toward the end of the fast, which limits the amount of fat burning that occurs.
However, if you consume fewer calories than you burn, a 12-hour fast can still help reduce body weight, stored fat, and support your weight loss goals.
Are other fasting methods worth trying?
Some people experiment with schedules like alternate day fasting, the Warrior diet, or OMAD, but these fasting practices carry higher risks, are harder to maintain, and we don’t recommend them. Stick with time-restricted eating schedules like 12:12, 16:8, or 14:10 for safer, more sustainable results.
