In essence, intermittent fasting is a pattern of fasting and eating over a defined time period ⏰. It is not defined by certain foods, but as always we recommend nutritional ketosis during times of eating.
Intermittent fasting can be used as little or as often to suit your needs. You may even like to mix and match throughout the year, practicing some daily, and others monthly or yearly. All methods have been proven to be effective, but through research, trial and error, you will find the one that suits you best.
To help you decide, here’s a run through of the different types of intermittent fasting.
Daily Fasting or Time Restricted Eating
This is a sustainable method of fasting that can be incorporated into daily life. As a general rule, you restrict eating into a 4–11 hour window, while the remaining 13–20 hours are fasted. Essentially, you prolong your night time fast 🛌 by delaying your first meal of the day, or stop eating earlier in the day (or both). This type of fasting is normally done on a daily basis, but some people dip in and out of it, depending on their schedule.
The 16:8 is one of the most popular forms of intermittent fasting that can be easily incorporated into daily life. Simply, you restrict eating to an eight hour window with 2–3 meals, and fast for 16 hours.
For example, stop eating after dinner at 6pm, and prolong breakfast till 10am the following day, eat for 8 hours, and the cycle begins again. You can change the timing according to your schedule—perhaps you prefer to eat earlier or later in the day.
This type of fasting is very manageable and recommended for most people. 💪
The 20:4 is a type of time restrictive eating based on a 20 hour fast, with a four hour eating window.
Generally, you can eat to your heart’s content during the four hour feasting, but by default, it is difficult to consume too many calories during such a short time frame.
The four hour eating window typically happens in the evening, but can be any part of the day that suits you. For example, you can eat two meals between 2pm and 6pm, and fast for the remaining 20 hours.
This would be suitable for those who are confident with intermittent fasting, are busy day workers and don’t have time to eat, don’t feel hungry during the day, or find that eating makes them less productive and sluggish 😴.
20:4 can also be leveraged for those special occasions — whether you’re heading out for an evening meal, or about to feast on a delicious, banquet with friends and family. 🎉
Longer fasts are generally not done daily, but rather periodically. These types of fasts are suitable for those who find they can’t commit to a daily fast, but would like to incorporate it into their weekly, monthly or yearly schedule.
If you already practice time restricted eating, you may also include longer fasts throughout the year to enhance ketosis. 💪
5:2 / Fast Diet
The 5:2 or fast diet encourages fasting for 2 days of the week. For any two days, calories are restricted to 500–600 for women and men, respectively. Calories can be spread out across multiple meals throughout the day, or eaten all in one. For the remaining five days, eating is not restricted by fasting.
For example, you can eat normally throughout the week, except for Tuesday and Saturday, when you only eat 500–600 calories (2 meals of 250 calories, or one meal of 500kcals) in the day.
24 Hour fast
The key is to fast for 24 hours between each meal. For example, eat at 7pm on day one and fast till 7pm the next day. Alternatively you can choose to eat earlier (for breakfast or lunch), and fast for 24 hours till the next day. The idea is that you eat a meal each day, but allow your body to fast for extended periods. This type of fasting is usually done once or twice per week, but can be adopted more frequently.
36 hour fast
This is an extended version of the 24 hour fast. You eat dinner on day one, fast for the entirety of day two, and eat breakfast on day three. This type of fast can help jump start your transition into ketosis, or push you into a deeper state of ketosis. This can be done as little or as often as once a week, month or year.
Alternate day fasting
As the name suggests, this involves fasting every other day. On fasting days, eating is restricted to one meal of 500 calories, or complete fasting (without calories). Alternate days, you can eat normally (as with all fasting, nutritional ketosis is recommended for this time.) Long-term, this is an intense method of fasting, and likely unsustainable.
Spontaneous fasting / Skipping meals
This is one that I would recommend for anyone who is on the fence about intermittent fasting, or feels overwhelmed by setting restrictive fasting times.
This is a gentle introduction to intermittent fasting, which is led by your lifestyle and body. It is perfect for those who don’t like to feel restricted, or get disheartened if they don’t meet the criteria of their diet.
You simply allow yourself to skip meals if you don’t feel hungry, or too busy to eat.
Cooking and eating take up a surprising amount of time, and embracing this way of eating will give you the time to work on other things—maybe replace a meal with something you enjoy, like going for a walk or yoga 🧘♀️
Spontaneous meal skipping is an effective way to recondition the popular belief that we need to eat three meals a day. You will not starve if you skip a meal now and then!
The Bottom Line
No matter what intermittent fasting you decide to follow, remember that calories and food quality are still very important and shouldn’t be neglected. Often people can side-line food quality or over indulge on calories as they use intermittent fasting as a safety net. In the long run, this will not be effective and your health will be compromised.
Have fun and experiment with different forms of intermittent fasting to see which one you like best.
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I’m sure you’re curious about the science behind all this 🔬 Here are some recent medical publications about this topic: