Thanks to a growing body of research and mounting anecdotal evidence, many experts agree that fasting can provide numerous health benefits, from weight loss to blood sugar balance to managing diabetes, and more. However, there is less agreement on the right way to fast.

Rather than looking at fasting as a single dietary approach that has to be followed the same way for everyone, it’s more helpful to look at fasting as a category of strategies. And you can choose the right one for you, depending on your goals.

In this article, we’ll discuss various fasting strategies and the benefits and uses of each.

What are the Different Types of Fasting?

Traditionally, the term “fasting” always meant the same thing: abstaining from food and caloric drinks for any meaningful amount of time — usually anywhere from about 16 hours to a few days.

For the sake of this article, we’re going to break fasting into two main classifications that provide the most benefit:

  • Intermittent Fasting
  • Extended Fasting

Intermittent Fasting

Intermittent fasting (IF) has become the most popular form of fasting, as it's widely accessible and flexible depending on your specific goals and needs. This type of fasting involves cycling between periods of fasting and feeding. During IF, your "fasting window" is considered the period when you're not eating, and your "feeding window" is the period you are eating. There are several different types of intermittent fasting, including:

Time-Restricted Eating

Time-restricted eating is a popular type of intermittent fasting because you can use it daily. It’s great for people who are just starting their fasting journey or want to dive in more slowly.  

The most common fasting schedules are 16:8 or 20:4 (fasting: feeding), but you can even start with 14:10 or 12:12. The key is to choose a window of time that you'll be forgoing food and stick to it. An example of a 16:8 fast may look like this:

  • 10 am breakfast
  • 1:00 pm lunch
  • 6:00 pm dinner
  • Then fast overnight until breakfast at 10 am again

This allows for a full 16 hours of fasting before breaking your fast the following morning. While you can incorporate feeding-fasting windows into your daily schedule, some people prefer to eat regularly on the weekends and use fasting windows during the week. Or, you can try this technique every other day — whatever you feel like you can realistically stick to.

24-Hour Fast

A 24-hour fast is typically only incorporated once or twice per week or less. This type of fast is pretty straightforward — unlike the feeding-fasting windows with a 24-hour fast, you go a full 24-hours with no food. 

This may seem a bit daunting at first, but keep in mind that a 24-hour fast is different from a 36-hour fast in that you still get to eat food each day. For example, a 24-hour fast could start after dinner at 6 pm on a Monday and end at 6 pm when you have dinner Tuesday.

Unlike a 36-hour fast, where you would go an entire day without food, 24-hour fasts are easier to incorporate for many people. For example, should you decide to skip dinner on Tuesday night and fast through the night, you would be extending the fast beyond the 24-hour mark, making it an extended fast. 

Alternate Day

Alternate-day fasting involves switching between fasting days and feeding days. Some people will simply do it every other day, while others may choose specific days per week to fast (like Monday, Wednesday, Friday). 

A popular modification for alternate-day fasting is switching between days of normal eating and then days of reduced calorie intake (usually around 500 calories per day). On your "fasting" days, you don't go entirely without food but may consume only one meal or a couple of small meals throughout the day. 

Extended Fasting

Extended fasting is a bit more straightforward than intermittent fasting. In the case of extended fasting, the only flexibility is really how long you decide to fast. Any fast that extends beyond the 24-hour mark can be considered an extended fast, with the shorter ones lasting around 36-hours and longer fasts lasting for several days. 

During an extended fast, the only thing you'll consume is water — no food or caloric beverages. 

What makes extended fasting feel different than intermittent fasting (besides the length of time, of course) is that during an extended fast, you may start to notice more dramatic symptoms of food withdrawal than you would while fasting intermittently. 

Depending on the length of the fast, you'll likely feel more hunger pangs, and as the fast goes on, you may also notice a substantial dip in energy accompanied by some brain fog. The reason for this is due to a metabolic shift that's taking place within your body. The longer you fast, the more your body will switch into a state of ketosis. 

Ketosis occurs as your body runs out of glucose and begins to make energy from your fat stores (called ketones). While most people have plenty of fat stores to pull from, your body takes a few days to adapt to ketosis, which creates a lag in energy production. This is why you may feel like you hit a wall on the second or third day of an extended fast. Your body will eventually adapt if you continue to fast, and your energy will begin to normalize.

While you should always consult with a healthcare practitioner when trying new diets, this is especially true if you're about to embark on an extended fast. Extended fasting is not recommended for people who don't have much fat as their energy sources won't support going without nourishment for days on end.

It's also important to note that your stomach will shrink significantly on an extended fast. So, when it comes time to reintroduce food, you should do so gradually and mindfully – this is not a time for a big steak dinner or an all-you-can-eat buffet.

What Are The Health Benefits of Fasting?

There are several research-back benefits of fasting. The more you fast, the more benefits you'll receive. With that being said, it isn't always necessary to do long or extended fasts to see shifts in your health. Some of the most prominent benefits of fasting include[1][2][3][4][5][6][7]:

  • The modulation of genes involved in metabolic syndrome
  • Improved insulin sensitivity
  • Improved fasting glucose levels
  • Improved blood pressure 
  • Reduced oxidative stress  
  • Weight loss
  • Enhanced autophagy (cellular recycling) 
  • Improved cognitive health and neuroprotection

The Takeaway

There isn't necessarily one "best" way to fast. In fact, there are so many different ways to fast because everyone has unique needs and goals. Ultimately, the best way to fast is a fast that you can stick with. If it feels doable, then you'll get the most benefit. 

Many people find that starting with shorter fasts and then slowly adding on the hours helps in the adjustment. If you're not accustomed to going hours without food, jumping into a longer intermittent or extended fast can be challenging. 

And whether you choose alternate-day fasting, time-restricted eating, a 24-hour fast, or an extended fast, it's always important to check with your healthcare practitioner before trying something new.

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