For anyone interested in doing intermittent fasting to experience its many benefits, the good news is that there are various types of intermittent fasting methods to choose from. Some involve shorter fasts while others are more advanced.
At the end of the day, the best option will depend on your goals, experience level, and what your schedule or routine allows.
In this guide, we’ll discuss different types of fasting, how they work, and who they’re recommended for. But first, let’s do a recap on intermittent fasting.
What is Intermittent Fasting?
Intermittent fasting or IF is a lifestyle practice where you avoid foods and drinks with calories within a specified time. It’s a voluntary act of abstaining from calories, unlike starvation. One is therapeutic while the other is harmful to your health.
People fast intermittently for at least 12 hours and can go as long as 36 hours if they want to induce autophagy — the body’s “housekeeping mechanism” in which it removes damaged cell parts, proteins, and pathogens that trigger inflammation (*).
After this fasting period, you resume eating your meals, which are supposed to be healthy and nutritious, to avoid canceling out the benefits that your intermittent fast provides.
Speaking of which, fasting has been used as a healing method in human history. The Greek physician Hippocrates (460-375 BC) prescribed strict fasts to people who had fevers and diseases in the acute stage. His patients didn’t consume anything except for water and herbal teas (*).
Fast forward to modern times, we use intermittent fasting to promote many positive changes in the body. Weight loss is one popular benefit. In fact, a systematic review of 40 studies has shown that people can lose 7-11 pounds over 10 weeks (*).
Improved metabolic health, blood cholesterol profile, reduced insulin resistance, and lowered blood pressure are some of the important benefits of intermittent fasting that go beyond weight loss.
While fasting is great for most people, not everyone can do it. Underweight individuals, women who are pregnant or breastfeeding, and those with a history of an eating disorder should not fast.
Moreover, people who are taking medications for their blood sugar or blood pressure should first talk to their doctor. Going without food for hours causes blood sugar and blood pressure to drop, which is why medical supervision is important.
Apart from that, you’re free to choose from the different types of fasting below.
9 Types of Intermittent Fasting
Before checking out the intermittent fasting schedules, know that each fast may cause you to experience increased hunger, cravings, headaches, mood swings, and low energy.
These side effects are similar to keto flu symptoms (which you experience when you go on the keto diet for the first time). Minimize them by staying hydrated with water and calorie-free electrolytes.
You could also ease your way into intermittent fasting by starting with the shortest fast, which is the first item on our list.
1. Overnight Fasting
Overnight fasting is fasting for 12 hours, followed by a 12-hour eating window. An example would be ending your last meal of the day at 6 pm and resuming the next meal at 6 am the next day.
Since this fast includes the hours you sleep, it’s the simplest option for newbies. Think of it as eating dinner and breakfast early.
Also, this type of fast is less likely to affect your workouts. Because of the relatively small fasting window, there isn’t a lot of adjustment to be made to your workout type, duration, and intensity. You can exercise while fasting (just don’t do it late at night) or do it during your feeding window.
Perhaps the only thing you’ll need to worry about is not getting nighttime snack cravings. If this happens, drink a caffeine-free herbal tea — it’s known to reduce appetite and also promote weight loss (*).
2. 16:8 Fasting
The 16:8 method isn’t just highly popular, but it’s also considered the best intermittent fasting for weight loss. It involves abstaining from food for 16 hours, then eating within an 8-hour window. For example, not eating after 8 pm and eating by 12 noon the next day.
A 2016 study found that after 8 weeks of limiting their calorie intake within an 8-hour window each day, the subjects lost body fat compared to those following their usual eating schedule (*).
Many people are able to go through 16:8 without major problems, except for the usual side effects (hunger, tiredness, etc.) which can be managed through proper hydration and rest.
If you’ve already started with a 12-hour fast and you no longer find it challenging, try 16:8 fasting. This will also help train your body to become metabolically flexible.
3. Alternate Day Fasting
The Alternate day fasting or ADF is a concept that was made popular by Dr. Krista Varady. It’s also called “the every other day diet” because it requires alternating between days of fasting and eating normally. For example, fasting on Mondays, Wednesdays, and Fridays.
There are two ways to do ADF: One is to fast completely (no calories at all) during your fasting day, and the other option is to limit yourself to only 500 calories during your fasting day. The latter is a modified version and it’s easier than a total 24-hour fast.
If you do the modified version of the ADF, prepare your meal ahead of time, making sure that it falls within 500 calories. There are plenty of nutritious meals that fit a 500-calorie plan, such as eggs, fish, beef, and leafy greens.
The modified ADF is great for people who would like to fast but are taking medications and supplements that require food — e.g., some antibiotics, fat-soluble vitamins (A, D, E, K), and NSAIDs (non-steroidal anti-inflammatory drugs).
4. The 5:2 Diet
The 5:2 diet means that you eat normally for five days, then limit your calories to 500 kcal (for women) and 600 kcal (for men) on the remaining two days. You are free to pick when these two days will be. For example, 500-600 calories on Tuesday and Thursday or Wednesday and Friday.
Like other intermittent fasting methods, the 5:2 approach results in weight loss. However, it uses calorie restriction instead of a total calorie-free fast. It’s for anyone who wants to lose weight without doing any extreme approach.
Additionally, it’s easier to stick to over the long term because there’s no need to completely forgo food, and better than traditional calorie restriction where you limit calories during the entire week.
Examples of low-calorie foods for your two fasting days include eggs, bone broth, broccoli soup, brussels sprouts, lean meat, and berries.
5. Spontaneous Meal Skipping
This intermittent fasting method has no rules and allows you fast intuitively. In other words, eat only when you’re truly hungry instead of sticking to a schedule.
For instance, you could skip breakfast if you don’t feel hungry in the morning or skip lunch if you would rather work through lunch.
Spontaneous meal skipping saves time on meal prepping (and money too if you’re always eating out). Plus, it’ll make you realize that skipping breakfast or another meal isn’t bad for your body — in fact, the opposite — as it gives your digestive system a break from food.
If you’re curious about intermittent fasting but you’re sure which method to start with, try skipping a meal.
6. 20:4 Fasting
Longer than the 16:8 method, this type of intermittent fast requires fasting for 20 hours and then eating within a 4-hour window. It’s closer to a one-meal-a-day diet (or OMAD) but between the two, OMAD is more advanced.
For instance, you could start fasting from 8 pm and break that fast at 4 pm the next day. You may break that fast with a small snack, such as eggs and bone broth. Then have dinner at around 6 or 7 pm. If you’re going to do another 20:4 fast, don’t eat anything after 8 pm.
It’s difficult to fit your usual calorie intake within 4 hours, which makes this a great strategy for improving weight loss or breaking through a plateau.
Also, the 20:4 fast helps you enter ketosis whether as a new keto dieter or if you’ve gotten off-track by eating too many carbohydrates. If not for ketosis, you can use it for special occasions — before heading out to a dinner party.
7. OMAD
The OMAD or one-meal-a-day diet is exactly what it sounds like. You eat all your calories in just one meal. For example, eating only dinner, let’s say from 5-6 pm, a few days a week.
You might be thinking that OMAD is an extreme form of intermittent fasting — yes, it is — which is why it’s not advisable to practice it daily. Instead, incorporate OMAD only a few days a week or alternate it with a different type of fast, like 16:8 or an overnight fast.
Since you’ll be eating only once a day, make sure to eat a nutrient-dense meal with healthy fats, proteins, and carbohydrates. Avoid blood sugar spikes by focusing on low glycemic carbs, such as green vegetables, avocados, cucumbers, and mushrooms.
Note that OMAD can be dangerous for people who have diabetes and taking glucose-lowering medications. If you’re a type 2 diabetic and would like to do OMAD for diabetes management, speak with your healthcare provider first.
8. 24-Hour Fasting
The 24-hour fast is a more advanced intermittent fast. It’s best for people who’ve previously succeeded with shorter fasts and want to take things to the next level.
You can choose which day of the week and time to do it — e.g., from 8 pm dinner on Tuesday to the following day’s 8 pm dinner. You get the idea.
As you approach 24 hours, your ketone levels continue to rise. Your body continues to burn through its stored fat for energy. Autophagy happens as you reach 18-20 hours of fasting. This is when your dysfunctional cell components are removed, allowing your cells to function more efficiently.
People who do not like to fast every day (perhaps only once a week or a few times a month) can do a 24-hour fast. Since this is a longer fasting regimen, you can expect to feel hunger and intense cravings hours after your last meal.
Manage hunger while fasting by staying hydrated. Black coffee is fine as well, including herbal tea and calorie-free electrolytes.
9. 36-Hour Fasting
The 36-hour fast, also called a monk fast, is when you abstain from food for 36 hours. However, you’re allowed to drink black coffee, tea, and other calorie-free drinks to curb hunger, stay alert, and maintain proper hydration.
As you can tell, this is the most difficult among the different types of intermittent fasting. It also puts you at risk of dehydration if you don’t consume enough fluids. On that note, it’s obviously not a good idea to do dry fasting on a 36-hour fast.
On this fast, you enter a deeper level of ketosis and increased autophagy. Starting your intermittent fasting journey with shorter fasts will help your body adapt to this method.
Do keep in mind that when you break a 36-hour fast, begin with a smaller meal. Focus on protein because it’s easier to digest. Eating a large meal right away and doing it too quickly can result in diarrhea. Remember, you haven’t had any food for more than a day.
Moreover, you’ll want to save those workouts for your feeding window. Exercising in the middle of a 36-hour fast would be extremely difficult.
The Bottom Line
Intermittent fasting is a great way to improve your health. We hope that with the different types of fasting discussed in this article, you’ll be able to find one or more that aligns with your goals and preferences!
Before embarking on fasting, consult your doctor who can help you start safely. Intermittent fasting should be done under the supervision of a healthcare provider if you have diabetes or another medical condition.