The Facts Of Fasting

What You Should Know Before Starting Your Own Fast

Going without eating for 16 hours can be tough if you’re not used to it. 24 hours without food can feel completely unattainable. However, with the right preparation and mindset, patients can achieve the vast benefits that come from fasting, including optimized blood pressure, improved blood sugar control, healthy weight loss and more.

We’re going to walk through what defines a fast, the types of fasting options and the positive results that can be felt when a fast is completed properly. 

Jump To A Specific Section:

• What Is A Fast?
• What is mTOR?
• 24-Hour Digestion Timeline
• What Is Allowed On A Fast?
• The Benefits Of Fasting
• Who Should Avoid Fasting?
• The Different Types Of Fasts
• Fasting For Menstruation
• How To Prepare For A Fast?
• Busting Myths About Fasting

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What Is A Fast?

Fasting is the voluntary restriction of food and/or drink intake for a certain period, typically 16 hours or more. Some types of fasts can last for days or even weeks, and may involve the intake of certain liquids such as water or juice.

While the purpose of a fast can vary, one major health benefit of abstaining from calories for a prolonged period of time is the suppression of mTOR to stimulate autophagy and give the body a much-needed break while it rebuilds stronger. 

“Your gut cells will not rejuvenate if you’re constantly giving them food because they can never rest. All of your organs need rest because that’s when they regenerate. But they also need stress; you have to stress the muscle or organ so it can build back stronger. One of the ways to stress the organ is fasting.”

-Dr. Marguerite Weston

What Is mTOR?

Mammalian Target of Rapamycin (mTOR) is the regulating protein associated with fasting that responds to growth hormones and nutrients, specifically amino acids. When fasting, mTOR activity is suppressed and autophagy occurs. Autophagy is the natural breakdown of damaged cells by the body. mTOR can also be inhibited through exercise, supplements that mimic caloric restriction and medications. 

“By recycling old or damaged cells, the body becomes more efficient. If you have damaged parts of your cells, the body can take those in and the cell will work better; the mitochondria become more efficient and make more ATP and you have more energy.”

-Dr. Marguerite Weston

The 24-Hour Digestion Timeline During A Fast

• First 4 Hours: we use or store what we eat, which is why you don’t want to go to bed right after eating)
• After that is depleted, the body uses the glycogen that is stored in the liver
• At 16 Hours: Your body is using protein to make glucose for a short amount of time before switching to fat as a source
• Up To 24 Hours & Beyond: Once the glycogen is gone, we go into Ketosis — a process in which our bodies burn fat as fuel because the carbohydrate supply is exhausted

Note: Some people have a large amount of glycogen stored which means it can take a day or longer to get into Ketosis. The goal is to easily go back and forth between normal and this state.

What Is Allowed On A Fast?

This depends on why you are fasting. If you are doing it to optimize gut health, anything your gut has to digest will break the fast. Black coffee and herbal teas are considered fine. Lemon, vinegar and sparkling waters are usually OK.

Stevia and other natural sweeteners may be allowed but this depends on if they spike glucose levels, which requires a test to know for sure. They should be avoided if you notice a spike.

Does Bone Broth Break A Fast?

Yes, bone broth technically breaks a fast, especially if you’re fasting for growth hormone production purposes. Bone broth contains protein so the body is going to have to work to process it. If you’re doing your fast just for calories and weight loss, bone broth is considered OK. 

What Are The Benefits Of Fasting?

• Decrease system inflammation
• Improve blood sugar control
• Regulate blood pressure and cholesterol 
• Boost brain function
• Lose weight/support maintenance of a healthy weight
• Remove excess skin (by harvesting the extra protein found in loose skin) 
• Increase growth hormone secretion 
• Suppress tumor growth

“You get more benefits from doing a prolonged fast. A lot of people think they get autophagy from any kind of fasting, but you really have to get to about 2 days or more to see those benefits. Stem cells don’t become more active or rejuvenate until around day 3.”

-Dr. Marguerite Weston

Who Should Avoid Fasting? 

• Pregnant patients 
• Breastfeeding patients 
• Type 1 diabetics 
• People who take medications for blood pressure
• Individuals under the age of 18
• Patients with a history of Eating Disorders 

What Are The Different Types Of Fasts?

• 16:8 Intermittent Fasting/Time-Restricted Eating: 16 hours of abstinence from calories followed by an 8-hour window of eating (the most popular form of fasting)
• 20:4 Intermittent Fasting: 20 hours of abstaining with a 4-hour window of normal eating
• 5:1:1 Fasting: 5 days of 16/8 fasting, 1 24-hour fast and 1 normal day of eating 
• 5:2 Fasting: Any two days of the week are restricted for 24 hours, while the other 5 are normal 
• Extended Fasts: These are more intensive and can last anywhere from 7 – 30+ days. An extended fast is usually performed under controlled circumstances and is done for a specific medical reason. 

Fasting For Your Menstruation Cycle

Some women benefit by scheduling fasts around their menstruation cycle. One benefit includes balancing insulin sensitivity. Because insulin resistance goes up as Estrogen increases, fasting can help you experience less extreme ebbs and flows. Fasting can also help lower Estrogen in women with Estrogen Dominance; this helps regulate cycles.

Timeline For Fasting For Menstruation Benefits

• Days 1 – 12: Participate in any type of fast that has been beneficial for you before
• Days 12 – 20: Stick to Intermittent Fasting to avoid too much cycle disruption
• Days 21 – 28: Avoid fasting altogether

How To Prepare For A Fast

If patients are struggling, they can increase protein and healthy fat intake to help keep blood sugar levels balanced heading into their fasted state. It also helps to know that we really don’t have to eat every two hours like we may have been told!

When your fast is complete, do your best to not reach for carbs. This is an important time and, if you do so, you’re going to miss out on that valuable rebuilding period, you could experience brain fog and you will also likely need to take a nap right away. 

“You need to practice and work your way up! It’s ok to start slow and a 24-hour fast is a great goal. Ghrelin – the ‘Hunger Hormone’ — goes up when you’re hungry but goes right back down if you don’t eat. You have the same hunger that you would feel not eating lunch if you didn’t eat dinner. It doesn’t build up. If you can stay busy, you can get through it!” 

-Dr. Marguerite Weston

The Role Of “ProLon” To Make The Process Easier 

ProLon is a 5-day fasting-mimicking diet. These proprietary, prepackaged foods are designed to regulate the body’s nutrient-sensing pathways and inhibit mTOR. It basically gives your body some nutrients while it still thinks that it is fasting. This allows you to get the benefits of fasting without any potential muscle loss and mitigating some of the negative impacts on mood.

Mythbusting: Dispelling Misinformation About Fasting 

“I can’t do it because my blood sugar drops too low.”

This can be indicative of poor metabolic health and they need to fix their daily eating habits and then they would be able to handle it, but they have to start slow and spend more time preparing.

It’s helpful for these individuals to use a continuous glucose monitor to gauge their blood sugar. Knowing that your blood is quantitatively in the right zone can help keep you less anxious and more motivated. Some physical symptoms of “low blood sugar” early on may actually be mental — shaking, brain fog, irritability, etc.

You will likely experience an increase in cortisol, growth hormone and norepinephrine after 16 – 20 hours of fasting. This results in more energy and can cause someone to become shaky.

“I’m going to lose all of my muscle mass.”

During a fast, your growth hormone actually increases. This, however, makes how you break your fast more important. You’ve just gone through some autophagy. You’ve broken down some of the bad cells that you have. Your muscles act like a sponge with the increase in growth hormone — if you give them what they need (lean meats, healthy fats, fewer carbs) — you will build better muscle cells with more strength.

“Isn’t fasting just another fad?” 

No — humans have actually been fasting and experiencing the benefits of it forever. We didn’t have grocery stores before and would often go for long periods of time without eating. A recent study found a significant improvement in 10-year coronary heart disease risk among individuals who participated in fasting as part of Ramadan. Ramadan has been celebrated for more than 14 centuries. 

“Will Fasting Destroy My Metabolism?”

The opposite is true! Multiple studies have found that we gain a metabolic boost from short-to-mid-length fasts, including this one which found that the metabolism of patients who underwent a three-day fast was 14% higher at the end. 

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About The Author

Dr. Marguerite Weston is an experienced Functional Medicine Doctor in Columbus, Ohio. She specializes in hormone therapy, gut health optimization and sustainable weight management programs. Dr. Weston often employs fasting — in a safe and controlled manner — as a method to help patients improve their gut health, maintain healthy weights and live longer, better lives. 

Interested in learning more about the benefits of fasting? Dr. Jason Fung is a leading expert when it comes to The Fasting Method and is the author of acclaimed books, such as The Obesity Code, Life In The Fasting Lane and The Longevity Solution.