Fasting: Is It Right For You?

by | Jan 24, 2020 | 0 comments

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How Fasting Helps With Health

The thought of going without food for any period of time sounds awful! Right?! I mean, anyone struggling to lose weight and get healthy is already struggling weling of hunger and crankiness. Who wants to be subjected to long periods of time without food. How would we even function?

Why Eating All The Time Is Unhealthy

If you are anything like me, you may have the mindset that eating small meals throughout helps to keep your metabolism up and constant calories are needed to stay away from “starvation mode”. Do not skip breakfast, it is the MOST important meal of the day! Make sure to have a protein bar after you work out. Need to replenish all the energy you used.

So, breakfast may be the best time of the day to have a hearty meal, but overall we eat way too much and way too often! Believe me, I was there too. I woke up hungry and went to bed with a full stomach from snacking.

Well, that “way” of thinking is far from the truth. We do not need to eat as much as we do, but we certainly should not be eating ALL the time. Let me explain why.

As you will learn in the blog, fasting may be the single most effective way to not only control weight, but also promote longevity and prevent chronic illness.

What us up with all the buzz about fasting these days?

There has been a lot of talk about fasting in the media over the past couple of years. And, whenever there is a lot of talk, I get a little skeptical (especially when it sounds unpleasant). But, I have not been able to ignore the multitude of scientifically backed research that is promotes fasting. So, I went a bit deep into the topic of fasting and was surprised to find great science backed information about the benefits of fasting for health.

I WAS a skeptic too.

A little history of my mindset at the start of this and why this is such a major shift in my thinking.

Back in my late twenties, I was doing a year long yoga teacher training program. Part of the curriculum was on Ayurvedic medicine and fasting. My experience with the actual fast was awful. I had a terrible headache, probably caffeine withdrawal and absolutely no energy! So, when this topic resurfaced recently, I was not really interested in delving into it. 

The more I have heard and read recently, I knew that this was not a practice to dismiss. There are significant health benefits for fasting. What is even more exciting, is that there are many different ways to fast and ways to prepare and build up to longer fasts to make them more comfortable and even something that feels good.

Fasting has been practiced for centuries. It may, in fact, be the simplest and most effective way to ward off ailments, such as diabetes, cancer and neurodegenerative disease, not to mention obesity. People have fasted when food sources were scarce and as religious and spiritual practices. This is not something new.

So, what actually is fasting?

Fasting is the voluntary absence of eating for health, spiritual or other reasons. Is is NOT starvation. You can start or stop a fast at any time and it has no standard duration as you will soon see.

Technically, when you are not eating, you are fasting.

What happens when we eat (this will help you to understand the benefits of fasting, so take a minute to read on)….

Food gets immediately broken down in the body, then used or stored.

If not immediately used, food energy gets stored as glycogen in the liver or as fat.

Carbohydrates and proteins when broken down into glucose, trigger the secretion of insulin (fat to a much lesser degree). Insulin is the gatekeeper to cells, allowing glucose molecules in the blood to enter the cells and be used as energy. The human body tightly regulates the amount of glucose in the blood because it can be highly toxic if levels get high.

Fats are directly absorbed as fat and have a very small effect on insulin.

Insulin is a major player in fat storage.

Insulin also helps to store the excess energy from food into the liver as glycogen. Once this limit is reached, the body turns excess glucose into fat for later storage.

***When we fast: Insulin levels drop. The liver then begins to break down glycogen for energy. FYI: Your body can store about 2,000 calories of glycogen which can be used for immediate energy.

After approximately 10-12 hours of moderate activity glycogen stores are low and the body signals the breakdown of fatty acids (fat stores) for energy. 12-24 hours experience 60% energy from fat with the biggest change at 18 hours. So, if you are “hungry” a few hours after eating….remember, your body has plenty of stored energy to use before you even get to fat burning for fuel!

What is Ketosis? The process of burning fat releases chemicals called ketones.

Eating three meals a day plus snacks for most people means you are never reaching ketosis. Insulin levels stay high, creating a constant metabolic growth state and fat stores are not mobilized for energy.

Constant intake of food throughout the day without triggers to use fat stores creates our body’s demand for glucose for energy. Over time, we rely on this constant stream of glucose energy and become metabolically inflexible. Some people, over time, will also become less sensitive to insulin if they remain constantly high. This then leads to insulin resistance, metabolic disease sets the stage for type 2 diabetes.

The GOOD Stuff: Why is fasting good for your health.

When we fast, our body is forced to use fats for energy, creating more metabolic flexibility, less insulin secretion and has the result of less oxidative stress.

Fasting also stimulates the body to clean up and repair. Fasting triggers systems within the body to hunker down. As an adaptive, evolutionary strategy, time with less food meant the need for increased clarity and better decision making, as well as a time to time to prioritize important functions within the body. The body is stimulated to implement a process called autophagy which eliminates cells that are no longer working properly and getting rid of metabolic waste. The body can then really focus on only what is vital to function at an optimal level.


This is an evolutionary process that has helped to increase the odds of survival. These adaptive responses that promote a better functioning body and health, are rarely prompted by our recent culture and lifestyle. In fact, the body is often in a constant phase of growth with the amount of glucose it processes on a daily basis.

One of the mechanisms that has been identified that is triggered by high caloric intake, especially proteins in the mTOR pathway. Specifically, when fasting the body inhibits the mTOR pathway, which is a major regulatory mechanism for metabolism and growth.  When amino acids (from proteins) are lacking, mTOR is inhibited, triggering a “survival” response, shutting down old cells or creating autophagy – the major mechanism for digesting the garbage your body has been holding on to.

Activity of mTOR, our growth pathway is associated with increased glucose, insulin and proteins in the diet. This turns off autophagy.  Therefore, constant food consumption and nutrient intake suppresses autophagy. If we are constantly in a renewal state and never “cleaning up” the old cells, our body’s do not run as well. This is associated with cancer and aging.

This is how fasting stimulates autophagy, a highly effective way to stimulate anti-aging mechanisms in the body. Fasting also stimulates growth hormone which helps to not only break down certain damaged cell parts, but also the creation of new parts.

Autophagy may also be a key component in the prevention of Alzheimer’s Disease which is caused by the accumulation of amyloid beta proteins in the brain. Autophagy removes these clumps of proteins that interfere with the nerves synaptic connections. 

The body responds to the “stress” of fasting – an adaptive, survival response that helps to clear up waster and dying cells. This is HIGHLY beneficial to our overall cellular health.


Summary of the benefits of fasting:

  1. Release of BDNF (brain derived neurotrophic factor) which helps to repair and create new neural connections.
  2. Regularly reducing insulin levels improves insulin sensitivity the opposite of insulin resistance which leads to metabolic disease and diabetes.
  3. Adrenaline is released in the process of using glycogen and fat stores, which revs up our metabolism and gives us more resting energy.
  4. Autophagy –  Fasting helps to flush out bad cells, garbage associated with metabolizing sugars and growth, and spurs regeneration of cells. In brain, blood, liver, and pancreas.
  5. One well researched fasting regin (The Fasting Mimicking Diet by Valter Longo), has been shown to help regenerate insulin-producing beta cells, induce cellular cleansing start the process of new tissue renewal. (Increased levels of glucose, insulin and proteins turn off autophagy). 
  6. Fasting helps to take out the amyloid beta proteins associated with Alzheimer’s disease and may prevent Alzheimer’s Disease.
  7. May prevent cancer – Autophagy may play a role in reducing cancerous cells.
  8. Increased insulin sensitivity. Reduced blood pressure and heart rate. 
  9. Lessens fatty liver.
  10. Increased fat burning, reduces obesity. 
  11. Reduced inflammation.
  12. Decreased atherosclerosis.
  13. Slowed aging. 

There is no doubt that fasting has numerous and widespread benefits on the human body for both weight loss and reducing chronic illness. 

Fasting Infographic

Quick guide to fasting.

There are so many different ways to fast. Which is the best?

There are many types of fasting. Intermittent, prolonged, alternate day etc. Let’s discuss a few different types and which ones may be a better fit for you. Some people will refer to intermittent fasting as time restricted eating (TRE) or time restricted feeding (TRF) and longer fasts as intermittent fasting. Fasting, by definition, is the time between eating. So, whether it is time restricted eating, intermittent fasting or fasting, we are talking about the same thing – the window of time between eating. Each window and method has different pros and cons. 

  • Intermittent fasting is a common term used today for the periodic fasting that usually occurs on a frequent basis and the regimented eating in a smaller window. Intermittent fasting (IF), can be long or short. Shorter fasts may be 12/14/16 hours in which time eating is daily and fit into a regular life schedule.  For example, a 12 hour fast or eating within a 12 hour window. A 14 hour fast is fasting for 14 hours – stopping eating at 7 pm, for example and not eating again until 9 am. These windows of fasting on a daily basis allow for a longer period of lower insulin throughout the day which is a powerful way to reduce insulin resistance and obesity. Longer fasts are usually done less frequently. 24 hour fasting is one example. Eating dinner to dinner, skipping breakfast and lunch. Some people do this on a weekly basis. These shorter fasts are easier to fit into daily life and work schedules and are beneficial, but may not realize all the benefits of longer fasting periods.
  • Longer fasts give quicker results – reduced insulin levels and weight loss. There is also a higher risk for complications. Anyone fasting for a period of time should not feel sick. So, medical issues should be discussed with and followed by a medical professional prior to fasting for a period of time. For example, people with diabetes or on certain medicines should at least talk to their doctors prior to fasting. Hypoglycemia can occur and is very serious. Signs are lightheadedness, confusion, sweating, hunger and weakness. This can lead to loss of consciousness, seizures and death if left untreated.  While low blood sugar is desirable, if you are on medicine that lowers blood sugar while fasting, you may be overmedicated – so, you need to discuss this and be monitored by a medical professional. Longer fasts may be carried out for 48 to 36 hours or even longer.


  • 5:2 Diet Period of low caloric intake created by Dr. Michael Mosley and author of the Fast Diet. 5 days of normal eating, then 2 fasting days with 500 calories of eating. This fasting method calls for 5 days of normal eating then 2 days of low calorie 500-600 calories (consecutive or spaced apart). This diet allows for decreased calories to help with compliance while still having the same hormonal benefits of fasting. This type of fasting is usually followed even after the target weight loss has been achieved.
  • 20 hour fast -This fast is a daily schedule of eating in a 4 hour window is based on “The Warrior Diet” book by Ori Hofelmekler. Based pon spartan and Roman tribes, all meals are eaten in a 4 hour window in the evening.
  • Fasting Mimicking Diet ™  created Valter Longo of The Longevity Diet is a five-day calorie restricted regimen may be better for people with leaky gut, reduces some of the risks of a water only prolonged fast and is highly researched. This fast will come at a cost and everything you need for the five day fast. It has the same physiological effects as a full fast with proper nourishment, so reduces the risks associated with prolonged fasting.
  • Alternate day fasting is not eating within a 24 hour period and then eating without restriction within a 24 hour period. This may be modified by having a reduced calorie eating window every other 24 hour period.

Do not fast if you:

  1. Are severely malnourished – body fat is below 4 percent or a BMI under 18.5.
  2. Have eating disorder.
  3. Are under 18 years of age.
  4. Are pregnant or breastfeeding.

Discuss with your doctor before fasting if:

  1. You have Gout, Diabetes, GERD.
  2. You are taking certain medicines.


If you are interested in all the How Tos of Intermittent Fasting, I suggest: The Diet Doctor or read “The Complete Guide To Fasting” by Dr. Jason Fung.

If you would like to experiment with the health benefits of a longer fast with a  program that has been well developed and generally tolerated well, I suggest “The Longevity Diet” by Valter Longo, PhD. The diet can be purchased here: ProLon

Other references I used for this post are:

David Sinclair, PhD (2019) “Lifespan: Why We Age- and Why We Don’t Have To”

Ben Greenfield (2020) Boundless: Upgrade Your Brain, Optimize Your Body & Defy Aging”


This site contains affiliate links. Click here to read my disclosure policy.


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Hi, I'm Heather

Hi, I'm Heather

I hope to inspire others like me looking to have it all. Working around the important things in life, rather than the other way around. I hope to share the struggles, successes and inspiration I have learned along the way and will continue to learn as I progress through this amazing journey.

The information provided on this website is for educational and informational purposes only. It should not be used as a substitute for the advice of an appropriately qualified and licensed practitioner or healthcare provider.