Fasting refers to the deliberate abstention from food and/or fluids for a period of time, for therapeutic purposes. Many people don’t know that fasting has been used for thousands of years in various religious and spiritual practices throughout human history, and in a sense, fasting is part of everyday life. The term ‘breakfast’ is the meal that breaks the fast, which is done daily.
The recent increase in scientific research around fasting has allowed us to understand just how fasting positively affects our physiology, cells, aging, disease and overall health. What has been incredible for me to watch in my own clinic and coaching is how many people, regardless of symptoms or condition, have benefited from this completely free and simple biohack!
In 2016 Dr. Ohsumi changed the fasting landscape dramatically when he won a Nobel prize for his work on autophagy. Autophagy means “self-eating” and is the body’s way of cleaning out damaged cells in order to regenerate newer, healthier cells. Autophagy is like the fast track to healing and slowing the aging process. What does autophagy have to do with fasting? Well, fasting triggers this magical autophagy process. Essentially, fasting helps accelerate healing and gets your body to naturally repair itself!
What happens to your body when you fast?
When you don’t consume food or calories, the body looks for other ways to generate energy, such as drawing on glucose, ie. sugar stores. Once the glucose is significantly used up, the body’s metabolism changes and the body begins to burn fatty acids from stored fat for energy. When this transition to burning fat for energy is made, the body begins producing ketones and is said to be in a state of “ketosis”. You can measure your level of ketones using a Keto Mojo (more about this later).
Once you reach a state of ketosis, many of the benefits of fasting start to kick in. Now, the specific benefits can vary depending on how many hours you have been fasting. For example, growth hormones kick in at 13 hours, whereas autophagy is thought to kick in at 16-18 hours. MIT research shows that at 24 hours intestinal stem cells will begin repair and 24 hours is also when you start to see weight loss.
You can learn more about what happens to your body hour-by-hour during fasting, and download this Fasting Benefits Chart.
What are the benefits of fasting?
Fasting can provide significant health benefits, for a variety of health issues, symptoms and conditions. Because fasting works to repair and heal on a cellular level, research suggests that it can help conditions like obesity, diabetes, sleep apnea, some types of cancer, Alzheimer’s disease, arthritis, asthma, multiple sclerosis, IBS and chronic or autoimmune conditions.
Fasting can help with the following:
The 7 Different Types of Fasting
There are 7 different types of fasting that I work on with my clients and teach in my Reset Academy. Each of the 7 different types of fasts have slightly different benefits and parameters on how they work. So if you’re wondering how long you should fast, the answer is it will depend on what benefit you are trying to achieve and which fast you pick.
- Intermittent Fasting. Intermittent fasting (IF) is the deliberate cycling between periods of fasting and eating. Most people already fast an average of 12 hours a day, that’s from dinner to breakfast the next morning (ie. mostly while you’re sleeping). With IF, what you will want to do is extend your breakfast slightly, starting one hour at a time, till you are fasting about 13-15 hours. The easiest way to do this is pushing breakfast back a couple of hours or skipping breakfast entirely and breaking your fast with lunch. There are so many benefits to IF and it’s something that I recommend clients do every day (yes, every day). The New England Journal of Medicine (NEJM) published a great review article discussing the benefits of intermittent fasting and how time-restricted eating contributes to healthy living.
- Autophagy Fasting. Naomi Whittel in her book Glow 15 talks about autophagy fasting. Autophagy fasting entails 16-18 hours of fasting (this is considered the “sweet spot”). There are some additional key principles here you’ll want to follow. When you break your fast, you’ll break it with healthy fats. This helps keep your blood sugar stable and curbs hunger, allowing you to go another 3-4 hours without eating. You’ll keep carbs under 50g and protein under 20g (animal or plant). Naomi Whittel also recommends eating carbs later in the day. Autophagy fasting is great for a lot of people, here is more information on what it is and why you should try it.
- Dinner-to-Dinner. Once you’re comfortable with intermittent fasting, dinner-to-dinner is a great type of fast to try 1-2 days a week. This means fasting from after dinner until the next day’s dinner. Drinking water and maybe coffee during this fast is okay. Dr. Fung, the author of The Obesity Code, calls this “OMAD”, or one meal a day. What’s important to remember here is that the longer you fast, the more the body will reach into your stored areas of fat to burn fuel and the more ketones your body will create.
- Dry Fasting. Unlike the other fasts, during a dry fast you’ll also abstain from drinking any water or liquids. There are a lot of reasons why dry fasting is great. Research shows us it can decrease inflammation and increase BDNF. BDNF is fertilizer for your brain. Incorporating dry fasting into your weekly diet variation, for those of you that want better brain clarity, improved memory, and better mobility, this would be the one you would do. I recommend a maximum of 12-24 hours of dry fasting, however I do not recommend that you dry fast for more than 24 hours. Dry fasting is definitely for the more expert faster.
- 36-48 Water Fasting. The purpose of a 36-48 hour water fast is really to keep insulin down and go after stored sugar. One of Dr. Fung’s key strategies for releasing long-standing weight is fasting for these longer periods. If you are extremely weight loss resistant then you are going to want to implement the 36 hour fast on a weekly basis. Many of you will notice with this fast the beginning of stem cells being released. Stem cells are repair cells, so often I will have patients of mine do a 36 hour fast to heal a musculoskeletal injury. When you get to this type of longer fast, you can also start playing with cycling your fasts.
- 3-5 Day Water Fasting. The longer 3-5 day water fast does amazing things for immune and other chronic conditions. I recommend these longer fasts once a month when attempting to trigger your body’s own healing process. I personally do one of these quarterly. However be aware that this type of fast is for advanced fasters. So if you’ve mastered the other types of fasts and are ready to try a longer fast, here’s how you can prepare for a 3 day water fast.
- Fast Mimicking. The fast mimicking diet was popularized by Volter Longo and The Longevity Diet. In this study, Longo showed that limited calories and low protein also forces the body to release stem cells. I recommend fast mimicking to patients who want the benefits of a longer fast, but still want to be able to eat food. Fast mimicking is designed to attain fasting-like effects by keeping your carb, protein, and calorie intake low and your fat intake high. Fast mimicking can also be a great fast to train your body for longer fasts. If you’re curious about the fast mimicking diet, check out my Fast Mimicking Q&A
How long should you fast?
One of the questions I get asked most frequently is, “how long should I fast?” Well, that depends on what health benefits you are hoping to achieve. The longer you fast, the more the benefits add up.
However, that doesn’t necessarily mean longer is better for everyone. For example, if you’re hoping to increase ketones, a 17 hour fast may be what you need, however if you’re trying to heal a musculoskeletal injury, you’ll want to work your way up to a 72 hour fast.
Here are the benefits of fasting broken down by hours fasted:
- 13-15 Hour fast: A 13-15 hour fast is considered intermittent fasting and if you are new to fasting, this is where you’ll want to start. At 13 hours of fasting, your body will secrete growth hormone. The growth hormone assists in burning fat and slowing down the aging process. If you are looking for an anti-aging solution I recommend this level of fasting.
- 15 hours is when most people begin to create ketones. Ketones are a sign that your liver has moved burning sugar to burn fat for energy. Furthermore, ketones are neuroprotective and will go up to the brain, giving you energy and better mental clarity.
- 17-24 hour fasting offers the following benefits: cellular repair, detox, cancer prevention, gut repair, aids with anxiety and depression, and brain and memory loss.
- 17 hour fast: When you reach 17 hours without eating you will start to stimulate autophagy. What this means is the intelligence of your cells has been turned on and they are able to repair themselves. This is best for people with autoimmune conditions.
- 24 hour fast: At 24 hours, your intestinal cells reboot and GABA production occurs. GABA is the neurotransmitter known to relax our brain and help with anxiety. Our gut health is incredibly important in preventing autoimmune disorders and aiding in weight loss..
- 36 hour fast: The more you fast, the more it forces your body to burn glucose, insulin, and toxins that are stored in fat. I always say that it is better to have fat around your muscles than around your organs and this length of fast will force your body to burn stored glucose and insulin. 36-48 hour fasts is where to start to see fat loss, anti-aging, and an increase in dopamine.
- 48 hour fast: At 48 hours you begin to reset dopamine receptor sites. If you are feeling like your happiness level is not where it needs to be this is where you need to be.
- 72 hour fast: This is a 3 day fast when you feel like you just do not know what to do anymore. I have seen these fasts used for people with severe injuries and diagnoses that want to reboot their whole immune system where healing starts. At 72 hours your stem cells for the immune system are regenerating as well as stem cell production for musculoskeletal injuries.
Watch my full Youtube video to figure out which fast will work best for you, and download my fasting benefits chart that provides guidance on the benefits during each type of fast.
How to Start Fasting: 3 Steps for First Time Fasters
So you’re ready to start, the question now becomes, how do you begin fasting?
STEP 1: CREATE A FASTING WINDOW
I recommend beginner fasters start with intermittent fasting. Remember, ideally this means 13-15 hours of no food. Take a look at how long you are fasting currently, and try extending your fasting window by two hours by pushing your breakfast time back an hour and moving your dinner time up an hour earlier.
- Get a blood reader like the Keto Mojo for this step, and learn how to measure your blood sugar and ketones. You’ll take a reading right after you wake up and a second reading right before you eat your first meal. What you want to see is that blood sugar is decreasing and ketones are increasing. If this isn’t happening, you’ll want to try increasing your fasting window and also taking a closer look at your macros.
- Drinking water and maybe coffee during this fast is okay.
- Start counting your macro. I recommend using an app called the Carb Manager to do this. In this beginning phase as you’re getting used to fasting, start by decreasing carbs, like bread, pasta, fruit, cookies, etc, and stay under 50 net carbs. At the same time, work on increasing your intake of healthy fats.
STEP 2: INCREASE YOUR FASTING WINDOW TO 13-15 HOURS
Once you’re comfortably fasting 13-15 hours, you’ll want to streamline your macros a bit more. You’ll continue staying under 50 net carbs, but also under 50 net grams of protein, with 60% of your food coming from healthy fats. Drinking water and maybe coffee during this fast is okay.
Now, how do you know if you’re in nutritional ketosis and your body is beginning to secrete ketones? Your ketones should be reading at 0.5 or above. If you’re not seeing this, time and repetition is important here. Sometimes the body simply needs more time to acclimate in this step and make that conversion from sugar burning to fat burning mode. If you still find you’re having trouble getting into ketosis, you might have a congested liver.
STEP 3: INCREASE YOUR FASTING WINDOW TO over 17+ HOURS
You’ve made it to autophagy fasting! You’ll continue staying under 50 net carbs, however you will want to further reduce your net grams of protein to under 20 grams, with 60% of your food still coming from healthy fats. Drinking water and maybe coffee during this fast is okay.
After mastering autophagy fasting, you may want to move into the more advanced fasts like dinner-to-dinner, 36-48 hour or even 3-day water fast.
How to break your fast?
Depending on how long you’ve been fasting, you’ll want to make sure you break your fast, slow and easy. I recommend avoiding carbohydrates or foods that will spike insulin and blood sugar. Bone broths and high-fat foods like olives, avocado and nut butter are a great way to go. Also, you’ll want to avoid these foods during a fast as they may break your fast inadvertently.
Is there ever a time you should stop fasting? Yes! If your ketones get above 7, your blood sugar drops below 40 or you are not feeling well, you should break your fast. You can also try drinking salt water or taking a mineral supplement like MIN to help stabilize minerals during fasting.
There are some people who should be cautious about doing this, such as people with adrenal fatigue, complicated health conditions, or women the week before their menstrual cycle (because this is when we need carbs to create hormones).
Don’t forget to feast!
Finally, don’t forget about FEAST DAYS! Yay! The biggest mistake I see people make when they implement a ketogenic diet or fasting diet is that they forget that their body needs to cycle between feasting and fasting, so make sure you are including hormone and nutrient promoting feast day into your fasting lifestyle. Here is what a healthy feast day for me looks like!
If you want to learn more, join me in the Resetter Tribe on Facebook. Every month we fast together during Fast Training Week where I lead you through different types of fasts and host a community Q&A to troubleshoot any roadblocks in your fasting journey.