Dr. Anthony Gustin is a board-certified sports chiropractor, functional medicine practitioner, entrepreneur, podcast host, and founder of Perfect Keto.
The benefits of intermittent fasting (IF) are becoming increasingly well-known. From losing stubborn fat and curbing cravings, to lowering inflammation and improving your gut microbiome — intermittent fasting almost seems too good to be true.
Although it can be tough to abstain from food for long periods.
So, is there an easier way to get the benefits of intermittent fasting without going 16-24 hours without food or skipping your favorite meal of the day?
It turns out there are seven different types of intermittent fasting, tailored to fit your unique lifestyle and personality.
Below, you’ll dive into these methods and learn the advantages and drawbacks of each:
IF is especially popular in the keto community because it helps you burn through stored glycogen stores quickly. That means getting into ketosis faster.
The biggest benefit of intermittent fasting is getting the physiological benefits of calorie restriction without actually starving yourself.
When you get into a groove with IF, you’ll naturally eat fewer calories, experience fewer cravings, and get all the benefits of fasting.
Other benefits of IF include:
- Losing fat while maintaining lean muscle mass[*]
- Increased human growth hormone, which helps with fat loss, muscle maintenance and keeping your skin looking young[*][*]
- Improved blood sugar and insulin levels[*]
- Longevity and protection from chronic illness[*][*]
- Increased brain health[*
By now, it’s likely you want to get started on your IF journey. Or maybe you’ve tried fasting before, but you couldn’t keep it up over the long term. This article will help. Read on to find out the seven different types of intermittent fasting and which one is right for your body.
Different Types Of Intermittent Fasting: Which One Is For You?
If you never experimented with intermittent fasting, this is the easiest place to start. By definition, intermittent fasting simply means going for a prolonged period of time without food.
The most popular timeframe is called 16/8 intermittent fasting. That means you fast for 16 hours and keep an eight-hour eating window open.
Most people could get similar benefits just from skipping breakfast or dinner.
The idea that you have to eat three square meals per day is a little outdated, anyway.
Try skipping a meal and see if you can work toward the 16-hours fasting, 8-hour eating window. You might just start to feel amazing.
Like the 16/8 method mentioned above, there are various other eating windows (aka feeding windows) you can experiment with.
Let’s face it — you’re already doing this to some extent because you fast every day between dinner and breakfast the next day.
Here’s what it looks like:
If you eat breakfast at 9:00 a.m. and your last meal of the day at 6:00 p.m., you ate within a 9-hour window. Therefore, you will fast for the remaining 15 hours of the day.
The next logical step to intentional intermittent fasting is widening your fasting window and narrowing your feeding window.
You might want to try the 16/8 method, which might look something like eating all of your meals between 10:00 a.m. and 6:00 p.m.
Another example is the 18/6 method. With this one, you’re bumping up your fasting window to 18 hours, which might mean eating between noon and 6:00 p.m.
This is a great place to start if you’re getting serious about IF, but you’re not ready to go an entire day without eating. It’s also super easy to adapt to your unique schedule and lifestyle.
Alternate day fasting is just what it sounds like. You fast one whole day, then eat normally the next day.
It might look something like this:
- Monday: fasting
- Tuesday: eat normally
- Wednesday: fasting
- Thursday: eat normally
- And so on
According to the science we have on alternate day fasting, you can take one of two approaches:
- You can fast completely on fasting days, only consuming water, or
- You can eat super small meals up to 25% of your regular caloric intake. This equals about 500-600 calories for the average person. There’s a catch though — you shouldn’t include sugar or starches in this 25%.
The second option is considered “fasting-mimicking,” and there’s a small study that suggests it can help with weight loss and support heart health[*].
Alternate-day fasting is one of the more extreme approaches to fasting, and it can be tough for some people to follow.
If you choose to eat nothing at all on your fasting days, start by limiting your fasts to no more than two days per week.
Fat fasting is a great option for those who are already in ketosis or want to get into ketosis quickly. Think of it as the keto diet on steroids.
It’s also for you if you’ve been doing keto for a while and find yourself at a weight loss plateau.
In general, you only want to do a fat fast for 2-4 days, never exceeding five days.
Here’s how it goes:
- You eat 80-90% of your calories from fat only for 2-4 days
- Some people limit caloric intake to 1000-1200 calories per day
- Others will break this up into 200-250-calorie meals throughout the day
- There doesn’t seem to be an eating and fasting window involved, as long as you’re sticking to mostly fat
This may sound easier than going without any food for several days, but it’s still a challenging fast. But if you can picture yourself eating avocados and spoonfuls of cocoa butter for 3-4 days on end, this might be the fast for you.
Another way to get the benefits of caloric restriction is the Warrior Diet. Formulated by a man named Ori Hofmekler, a former member of the Israeli Special Force, the diet was meant to mimic diets of ancient warriors.
Presumably, these warriors kept their minds sharp and their waistlines slim by eating very little during the day and consuming one big meal at night.
If you follow a low-carb ketogenic diet, you may want to focus on low-carb veggies and keto snacks during the day, and one more substantial main meal at night.
You can also abstain from food entirely throughout the day and eat one large meal at night.
But, since small snacks are “allowed” before evening, this approach can be easier than forgoing food altogether. Just be sure not to overeat late at night, which can cause stomach upset and indigestion.
This type of fasting is — as the name implies — a full 24-hour fast.
That means, for 24-hours, you only consume water if you want to stay in a truly fasted state. Some people may add non-caloric beverages like coffee and tea. It’s up to you.
The timeframe of this particular intermittent fasting program is completely up to you.
You could start after dinner on say, a Tuesday evening, fast the following day, then enjoy dinner on that Wednesday evening.
As long as you don’t take in any calories for a full 24-hours, you’re fine.
This can be a good way to get into ketosis more quickly, but a 24-hour fast is also extremely challenging for most people. If you’re a beginner, you might want to start with a more moderate 12- to 16-hour fast to build up a tolerance.
The 5:2 diet is similar to the 24-hour fast and the alternate fast in that you will be fasting for 24-hour periods[*].
But it’s slightly easier in that you’ll only fast twice per week. It looks like this:
- You eat normally for five days every week
- You fast completely for two days per week or restrict calories to 500-600 calories per day on fasting days
- You choose when you fast; i.e., dive into one 48-hour fast or fast for two 24-hour periods, days apart
This is a little more extreme, so you may choose to take advantage of those low-calorie meals during the fasting period. Just don’t exceed about 500-600 calories per day to stay in a fasting-mimicking state. And remember to stick to healthy fats, protein, and veggies only so you don’t experience carb cravings or dramatic dips in blood sugar.
General Intermittent Fasting Guidelines
To get the most out of intermittent fasting, there are some good tips to keep in mind.
No matter what method you use, the “rules” are pretty similar:
- During fasting times, plan only to drink water. This will not only help you stay hydrated but also help reduce cravings and hunger. Even black coffee and other non-caloric beverages may kick you out of a fasting state.
- It’s essential to eat high-quality foods during your feeding windows, especially if your goal is weight loss or ketosis. See Perfect Keto’s list of ketogenic foods to help you stay in ketosis, and always remember to test your ketone levels regularly.
- Please ask your doctor before trying IF, especially if you’re pregnant, breastfeeding, under 18, or have any pre-existing conditions. IF isn’t recommended for anyone who has struggled with eating disorders in the past.
Intermittent Fasting: Where To Start
Intermittent fasting is a great way to lose weight fast, get into ketosis quickly, and low blood sugar and insulin levels.
But you can also benefit from these fasting methods if you don’t have body fat to lose. There are plenty of other brain- and immune-boosting benefits to fasting, and very few side effects if you play by the rules.
It’s an amazing way to limit caloric intake if you’re prone to overeating, and it’s way more enjoyable than counting calories.
Physically, some people find that fasting is even more effective than calorie restriction.
If you are new to intermittent fasting, start by skipping one meal. If this feels easy enough, try the 16/8 method. From there, you can continue to experiment with these different types of intermittent fasting to see which approach your body likes best.