Intermittent fasting is as simple as a schedule that divides your day into two parts: an eating window and a fasting window. While most diet plans are fundamentally concerned with WHAT you eat, this plan is all about WHEN you eat, and that’s it.
There’s no meal planning, no shopping lists or other advance preparation. You can customize your eating schedule based on your lifestyle, and then all you have to do is follow the schedule! The structure of intermittent fasting is meant to make the most of your body’s natural metabolic processes every day, so that you can be on your way to long term optimal health.
Intermittent fasting might just be the simplest diet you’ve ever encountered, and it has something for everyone–whether you’re looking to lose weight, increase your athletic performance or boost your brain health. In fact, the results are so potent, they almost seem to good to be true. We were skeptical too, so we’ve compiled a list of all the health benefits supported by scientific studies:
1. Weight loss and maintenance
By training your body to burn fat for energy, intermittent fasting will tap into your body’s natural weight loss mechanisms. Plus, the simplicity of the plan means you’re much more likely to stick with it!
2. Increased energy
Unlike so many calorie restriction diets that can make you feel sluggish, the intermittent fasting schedule is designed to regulate your hormones so that you’re always easily accessing stored fat for energy. No more afternoon slumps!
3. Increased mental clarity and focus
Intermittent fasting has the ability to boost your brainpower because it increases your BDNF, which supports brain connectivity and new neuron growth. (1)
4. Better cognitive function
The hormonal changes that occur when you follow intermittent fasting have actually been shown to provide protection against neuro-degenerative diseases that affect your memory and brain function. (2)
5. Regulated blood sugar and insulin levels
The quickest and most efficient way to lower insulin levels is through fasting. While you’re in your fasting window, no new glucose is being supplied to your body, which means your body has no choice but to use up stored glucose. (3)
6. Support healthy cholesterol and blood pressure
Intermittent fasting is an excellent prescription for heart health, because of its ability to support your liver’s cholesterol production at a healthy level. Studies have shown that 70 days of alternate-day fasting can reduce LDL cholesterol by 25 percent. (4)
7. Reduced inflammation
Your body relies on a process called “autophagy” to clear out old and damaged tissues and cells. When you fast and give your body a break from the constant effort of digesting food, it seems to be able to focus more energy on repair, which means alleviating inflammation in the body. (5)
8. Increased metabolic rate
When you practice intermittent fasting and successfully switch your body into fat-burning mode, your body is actually using adrenaline to release stored glycogen and access fat to burn. These increased adrenaline levels will speed up your metabolism. (6)
9. Long term anti-aging benefits
So you’ve decided to give intermittent fasting a try (congratulations!), and you need to know what the eating schedule is. Even just a quick online search probably gave you an overwhelming amount of information about the different kinds of plans, durations, days, etc…
With such a wide variety of intermittent fasting regimens, how can you figure out which one is best for you?
Not to fear, we’ve put together a helpful breakdown of the different schedules. After all, you want to make sure you’re choosing a schedule that works well with your lifestyle and can maximize the incredible health benefits that intermittent fasting can give you.
The 16/8 Schedule
This is easily the most popular of all the intermittent fasting schedules. It combines an 8-hour eating window with a 16-hour fasting window. So, for example, only eating between the hours of noon and 8:00 p.m.
Pro: This is the most common schedule for a reason. It fits pretty seamlessly into most lifestyles, seeing as how you can choose to skip either breakfast or dinner, depending on your personal preferences. Also, you’re sleeping during a good chunk of the fasting window, which makes it easier.
Con: 16 hours can be a long time to go without food when you’re new to fasting. After one or two weeks, most people hardly notice any more hunger pangs, but it does take your body a little while to get adjusted to this schedule.
Who it’s for: This schedule is suited for just about anyone, but especially if you’ve already experimented with shorter fasting windows, you might want to give this one a try. It tends to hit the sweet spot for most people as far as being manageable while still providing noticeable benefits.
The 12/12 Schedule
This is typically the best way to start out for anyone completely new to fasting. It used to be quite normal for people to fast for 12 hours. Dinnertime around 7pm, breakfast at 7am. Enter the advent of freezer food and late night snacks, not to mention the longer work days which cause people to stay up later.
Suddenly we are eating around the clock, and it’s wreaking havoc on our blood sugar and waistlines. Did you know that your body doesn’t actually switch from a “fed” state to the “fasted” state until about 4 hours after you’ve finished your last meal?
Pro: This schedule requires minimal effort. It is a great way to reset your body to what is more natural for it (giving your digestive system a break overnight). Plus, you’ll probably sleep better and you’re not likely to experience any hunger pangs with such a small fasting window.
Con: Because the fasting window is relatively small, you’re not likely to see as many health benefits as quickly as you would on a plan with a longer fasting window. This is because it typically takes your body anywhere from 8-10 hours after enjoying your last meal to get to a fasted state. Only then do you enter fat-burning mode. So with a 12-hour fast, you’re only going to be in fat-burning mode for maybe 2-3 hours.
Who it’s for: Anyone new to fasting or struggling with the idea of giving up food for too long.
The 20-Hour Fast (Warrior Diet)
A 20-hour fasting schedule has been popularized by the “Warrior Diet,” which was created by Ori Hofmekler. Inspired by the eating habits of ancient Spartan and Roman warriors, this plan requires you to eat all your food within a four hour window. So, for example, only eating between 2pm and 6pm. The Warrior Diet also encourages a focus on high-intensity interval training and a diet of unprocessed foods.
Pro: Because this is a pretty condensed intermittent fasting schedule, it can work really well for folks with a hectic lifestyle. You only have to worry about preparing and eating food for 4 hours per day, and the rest of the day you can just focus on getting everything else done. Also, many people report getting very deep and restful sleep when they follow this plan.
Con: It can be difficult for some people to go a full 20 hours without consuming any calories, especially when you’re just starting out with fasting.
Who it’s for: Someone who already has some experience with intermittent fasting but who is looking for faster fat-loss results. Also, there are online testimonials of folks who started with the 16/8 plan but found that they were still experiencing sugar cravings and a desire to overeat during the 8-hour window. These folks found great success with the Warrior Diet, because it is nearly impossible to overeat in a 4-hour eating window, given the limited space in your belly!
The 24-Hour Fast
Despite how it sounds, a 24-hour fast does not require you to go a whole day without eating. You will just be fasting from dinner one day until dinner the next day. Or breakfast to breakfast or lunch to lunch, depending on what you prefer. If you have dinner at 7pm tonight and don’t eat again until 7pm tomorrow, you’ve just completed a 24-hour fast.
Pro: This one can be very complementary to a busy day at work. Let’s say you have a super hectic day at the office or maybe a full day of travel. Instead of stressing about when and what to eat in the midst of your chaotic day, just take a break. Don’t worry about eating all day, until whenever you get home for dinner.
Con: You don’t want to do this one every day. It’s not recommended to do a 24-hour fast more than twice per week.
Who it’s for: People whose busy schedules could benefit from eliminating the stress of finding, preparing, eating and cleaning up food for an entire day, a couple days per week.
The 5:2 Diet
This plan is a little different than most traditional intermittent fasting schedules. Instead of completely abstaining from food during any set fasting window, you instead just dramatically limit your calories during a period of time. Specifically, you eat normally for 5 days of the week. On the other two days (your choice), women limit their calories to 500 for the day, and men stay below 600 calories per day.
Pro: You never have to face a time period where you’re not allowed to eat anything. This is a great plan to ease your way into the concept of fasting, without diving in all the way.
Con: You do have to be pretty precise about counting calories twice a week, which can be a pain. That means you need to look up the caloric content of everything you’re eating, measure out your portion sizes, and keep track throughout the day.
Who it’s for: People who enjoy the process of counting and tracking calories. (We know you’re out there!) This is also a great plan for anyone who is daunted by the prospect of having to face hunger pangs while fasting, because you never actually have to go without food on this plan.
Tim Ferriss 3-Day Fast Protocol
Tim Ferris has developed a three-day fasting protocol that is meant to accelerate your transition into ketosis, also known as fat-burning mode. Here’s what it looks like:
Stop eating by 6pm on Thursday. On Friday morning, go for a 3-4 hour walk while drinking lots of water. This should use up your body’s remaining glycogen stores, which will then transition you into ketosis. You don’t eat anything all day Friday and Saturday, but Tim does recommend supplementing with MCT oil or other ketone sources. You continue your fast into the daytime on Sunday and then break your fast with dinner on Sunday evening, right around 6pm. Tim’s protocol recommends doing this kind of 3-day fast once a month.
Pro: This plan has proven results for dropping people into ketosis much more quickly than other schedules. And because you stay in ketosis for several days, you can expect accelerated fat loss, plus reduced inflammation and increased autophagy (cell regeneration).
Con: Fasting for several days straight is not easy for the uninitiated. You also have to plan your day around being able to go for a long walk on the first full day of fasting. And, definitely expect to have lower energy levels throughout the fast.
Who it’s for: Anyone who’s highly motivated to get accelerated benefits of intermittent fasting. If you’ve already experimented with other schedules and maybe are looking for a kickstart to break through a weight loss plateau, this might be the right plan for you.
Alternate Day Fasting
This intermittent fasting schedule is actually a hybrid plan, where you can pick either the 16/8 schedule, the 12 hour fast, or the 20-hour fast. Then, instead of following that plan every single day, you would only adhere to your chosen fasting window every other day.
Pro: This approach tends to make any intermittent fasting schedule much more manageable and customizable.
Con: It might take a little longer to see health benefits, since you’re not switching your body into the fasted state every day. Please note: this doesn’t mean you won’t see benefits! Plenty of people get awesome results with alternate day fasting, and they find it much easier to sustain.
Who it’s for: Anyone not ready to commit to a full intermittent fasting schedule every day. Also, this approach definitely seems to work better for some women. You can read more about how intermittent fasting can affect women differently further below.
This is a more intense fasting approach, typically deployed in situations where there is physician oversight and you’re trying to regulate Type 2 Diabetes. It looks like this: Finish eating dinner by 7pm tonight, don’t eat at all tomorrow, and then have breakfast after 7am the day after tomorrow. Dr. Jason Fung has used this protocol with great success in helping those who suffer from Type 2 Diabetes.
Pro: Excellent success rate, over the long term, for managing insulin sensitivity.
Con: Quite difficult to implement.
Who it’s for: Primarily recommended for those trying to manage insulin sensitivity.