A Functional Medicine Guide To The 8 Types Of Fasting (+ Which One You Should Choose For Your Health)

When you think of “intermittent fasting” you may associate it with calorie restriction and unhealthy weight loss. I understand how the notion of skipping meals can be brushed off as a form restriction disguised as a wellness practice. But that couldn’t be further from the truth. In reality, intermittent fasting isn’t about punishment or restriction at all. In fact, it is one of the best things you can do for your health as it has been scientifically proven to reduce inflammation, improve metabolism, support heart health, manage blood pressure, increase energy, and so much more.

As a functional medicine expert and the author of the NYT-bestselling book, Intuitive Fasting, I have seen these benefits firsthand in my own life, and in the lives of my patients in my telehealth functional medicine clinic. So before writing this tool off as “not for you”, let’s dive a little deeper into what exactly is fasting, how it can benefit your health, and the various types of fasting so you can cultivate a practice that works with and for your health — not against it.

What is fasting?

Also referred to as time-restricted eating, fasting, is what it sounds like: going for an extended period of time without eating or drinking (or both). Ultimately, fasting looks different for each person, but essentially, going without food for longer than you normally do is considered fasting. The exact hours can vary, but the goal is the same and that is to give your body a break from eating in order to kick-start your body’s natural healing mechanisms to restore balance and reach a state of metabolic flexibility.

Health benefits of fasting

It’s hard to imagine that going without food for prolonged periods of time would be beneficial. But studies have found that intermittent fasting impacts key mechanisms that have wide-spread positive effects on multiple areas of our health. 

1. Ketosis

One of the main goals of reaching a fasting state is to put your body into a healthy level of nutritional ketosis — a natural metabolic state that kicks into gear when there’s not enough glucose in your blood to use for energy. The health benefits of being in ketosis include everything from fat loss and blood sugar balance to reduced seizures in people with epilepsy and lowered risk of some cancers.

2. Gut health

Did you know that digestion uses up 10% of your body’s total energy?! Chewing, making saliva, and swallowing all requires energy. And that’s just the beginning. Digestion requires your stomach to produce acid, hormones to regulate hunger signals, and enzymes to break down macronutrients.

When you are constantly eating throughout the day, your digestion isn’t given much of a break. Talk about burn out. But fasting gives our gut the rest it is craving. And not only that, fasting works to repair your gut at the very cellular level by:

• Restores your gut-metabolism connection: research also shows that fasting can reduce the absorption of bacterial endotoxins linked to insulin resistance and obesity risk. (1)
• Regulates your microbiome: Just like the ocean tides ebb and flow throughout the day, so do the different colonies of bacteria in your microbiome but continuous eating can throw off its normal pattern. Fasting can reset your microbiome’s natural ebb and flow.
• Improves gut inflammation: Systemic inflammation usually begins in the gut. While fasting lowers gut-specific inflammation in health problems like Crohn’s disease, it can also lower inflammatory markers like IL-6 and CRP that contribute to inflammation in other areas of the body besides just your gut. (2, 3)

READ MORE: A Guide To Intermittent Fasting To Heal Your Gut

3. Autophagy + Cellular Renewal

The idea that times of starvation are healthy might come as a surprise or feel counterintuitive. But as it turns out, when you fast, your cells enhance their ability to cope under starvation conditions, which makes them healthier and more resilient to disease overall. As long as you don’t overdo it and give your body time to recover, you will grow physically stronger in the face of controlled amounts of positive stress, including fasting.

Another benefit of intermittent fasting for your cells is autophagy. Think of this mechanism as your body’s “cellular housekeeping”, in place to clear out damaged cells in order to make room for new, healthy cells. And since your cells make up every single part of your body, cellular health is crucial if you want to look and feel your best.

4. Inflammation

With ketosis, autophagy, and gut health on our side, the potential health benefits of intermittent fasting are practically endless. But there’s also one very important benefit of fasting — the ability to help your body fend off chronic inflammation.

The reality is, a large majority of the healing process rests on decreasing chronic inflammation and unhealthy inflammatory responses. This is due to the fact that inflammation is the underlying commonality in almost every major disease and dysfunction in existence. It makes sense, then, that lowering chronic inflammation would be on the list of intermittent fasting’s key benefits.

8 types of fasting

Now that we’ve established all of the great things fasting can do for your health, let’s get into the different types of fasting, starting with the most beginner-friendly methods to the most advanced.

The 8-6 Window plan

This plan is what I typically suggest for people who have zero experience of fasting. Because you are still eating between the hours of 8 a.m. and 6 p.m. it is a great plan to start with since it allows you to eat breakfast, lunch, and dinner within normal hours while still getting 14 hours of uninterrupted fasting time in a day.

The 12-6 window plan

This intermediate intermittent fasting plan is similar to the 8-6 Window Plan but with an added 4 hours of fasting time. Instead of eating breakfast, you’ll extend your fast until lunchtime to give you a full 18 hours of fasting while only eating between 12 p.m. and 6 p.m.

The modified 2-day plan

This plan is structured a little differently than the first two. You’ll be eating clean for 5 days of the week (which days are up to you) and on the remaining two days your calories will be restricted to no more than 700 calories. This type of partial fast provides a lot of the same benefits as a full day of fasting, but can be easier to manage than a full day fast, especially if you have never done one before.

During the 5 days of eating you can structure your meals however you like but they still need to contain healthy fats, clean meats, vegetables, and if desired, some fruit. These are not “cheat days” and an excuse to eat whatever you want. Remember, this shouldn’t come with a restrictive mindset. Instead, it’s all about loving your body enough to nourish it with foods that love you back.

On restricted days you can structure your day however works best for you, whether that is smaller meals throughout the day or two moderate sized meals. Again, you’ll want to be eating healthy fats, clean meats, and produce, and food tracking apps can help you keep track of what you are eating so you don’t exceed 700 calories.

The 5-2 plan

Also known as the 5:2 diet, it is similar to the modified 2-day plan but you will be eating clean for 5 days of the week. However, the other two days you won’t eat anything for 24 hours. These days shouldn’t be back-to-back. For example, you’ll fast completely on Sunday and Wednesday so you aren’t accidently fasting for two days straight.

Every-other-day plan

This plan, often called alternate-day fasting, is pretty straightforward and has you alternate between days of eating and not eating. Even though this is intense it offers some amazing benefits. Same as the other plans, you’ll want to stick to clean, whole foods during mealtimes. You can also continue to have herbal tea and plenty of water on your fasting days.

OMAD

This plan is an acronym for “one meal a day”. This plan has you fasting for 23 hours straight before breaking your fast and eating all your caloric intake for the day in one hour, at one meal. Typically, people will break their fast for dinner but you can break your fast at any time of the day that works best for you.

24-Hour Fast

For this type of absolute fast, you don’t eat anything for a complete 24 hours. At no point are you “breaking” your fast with any sort of food. For example you can choose to fast from 8 a.m. until breakfast at 8 a.m. the following day.

Water Fast

In all of the types of fasting we have covered so far, unlike dry fasting, you can still drink water, even during a 24 hour fast. It’s actually encouraged. But what makes a water fast different is that in some select cases it can be done for up to 72 hours. It’s important to note that this type of full fast isn’t one I would typically recommend to someone without the guidance of a practitioner for specific health conditions.

SHOP: When fasting, it is even more important to keep your electrolytes balanced to avoid negative side effects and dehydration. But a lot of the electrolyte mixes are filled with sugar and other unnecessary additives that can throw off your fasting goals. That’s why I created Cellular Hydration with LongevityRX — the only leading brand with a balanced 1:1 ratio of sodium to potassium. Powered by Celtic Sea Salt®, this whole unrefined mineral blend is synergistically combined with red marine algae, organic watermelon, coconut water, and celery to provide hydration from head-to-toe.

What type of fasting should you choose?

There is not necessarily a “right” or “wrong” way to fast. Ultimately, choosing what type of fasting to practice depends on your level of past experience with fasting, your current health, and your particular health goals. But if you are just starting out, I always recommend starting off slow with the beginner 8-6 window plan and gradually work toward more advanced fasting protocols. 

It’s also important to talk to your doctor, especially if you have any underlying health problems, before starting a fasting plan to determine if it is the best choice for your health. While fasting offers amazing health benefits, certain people can be more sensitive to fasting (physically and emotionally) such as people with a history of eating disorders, have blood sugar problems, or are super active with greater calorie needs.

LISTEN: Rethinking Fasting: Myths, Metabolism, Hormones & Grace | Cynthia Thurlow

The Takeaway

Fasting doesn’t have to be complicated. One of the biggest benefits of fasting I’ve found is that it can cut out a lot of the food noise we face in our society and help us to reclaim our natural intuition around eating and our body’s hunger signals. By starting off slow and finding a type of fasting plan that works for you, you’ll be setting the foundation for sustainable weight management, greater metabolic health, and restored overall health.

As one of the first functional medicine telehealth clinics in the world, we provide webcam health consultations for people around the globe. 

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Sources

• Al Qassab, M., Chaarani, N., Hamou, A., Harb, R., Jradi, A., Zeineddine, M., Ghadieh, H. E., Khattar, Z. A., Azar, S., Kanaan, A., & Harb, F. (2026). The Gut Microbiota-Insulin Resistance Axis: Mechanisms, Clinical Implications, and Therapeutic Potential. FASEB bioAdvances, 8(1), e70080. https://doi.org/10.1096/fba.2025-00218
• Crohn’s & Colitis Foundation. (2026, February 9). Intermittent fasting cut Crohn’s disease activity by 40% and halved inflammation in randomized clinical trial. Crohn’s & Colitis Foundation
• Mulas, A., Cienfuegos, S., Ezpeleta, M., Lin, S., Pavlou, V., & Varady, K. A. (2023). Effect of intermittent fasting on circulating inflammatory markers in obesity: A review of human trials. Frontiers in nutrition, 10, 1146924. https://doi.org/10.3389/fnut.2023.1146924