The Science, History, and Mindset Behind Fasting

Updated: Oct 30, 2020

We all want to live in balance. We want to live a healthy lifestyle consistently. In this day and age, it can seem impossible to know what we need to be doing to live a balanced healthy lifestyle for the long run. Without creating healthy habits (versus quick, immediately gratifying changes), we will not maintain our progress in health. But what habits should we set out to create? In this article, we’ll investigate whether or not fasting is a healthy habit we should practice on a regular basis. This article will help you have everything you need to decide if fasting is right for you.

In recent years, fasting has become one of the hottest trends. While intermittent fasting has become very popular for weight loss, there are a lot who say we should eat every couple of hours to “rev up our metabolism.” Everything in the health and wellness industry seems to contradict each other. How frustrating is that! Everyone seems to have a different opinion on what YOU should be doing. So is fasting legit or is it just some extreme fad we should stay away from?

Before we answer that question, we must look at the topic through three main lenses: historical evidence, biblical principles, and current evidence-based research. Many people set out to research a topic, but only get a partial picture because they leave one or more of these approaches out. It is only when we look through all three of these lenses that we see the full picture.

Biblical- What are the motives and mindsets behind the topic? How does it line up with biblical principles? Is this topic consistent with the Word of God and/or the proven character of God?

Historical- When and where did a topic originate? What are its results throughout history? Looking at the past reputation of a topic is crucial in determining its validity for today.

Current Research- Do current scholarly studies provide evidence to support the topic? What are the cold, hard, objective facts about the topic and its effects?


Contrary to popular belief, fasting is not a new trend. It is actually an ancient practice that can date all the way back to the beginning of mankind. “Fasting is one of the most ancient and widespread healing traditions in the world.”(4) “From earliest antiquity, peoples scattered all over the world have, for one reason or another, abstained themselves from food and drink for a shorter or longer time, as individuals or as a community. Instances collected from many books on ethnology and history of religion are abundant."(7)

Image of Hippocrates

The question is, why? Why have people practiced fasting for thousands of years? Many times it was for religious reasons. Other times, people viewed fasting as a crucial wellness practice. "Fasting and other dietary regimens have been used to treat epilepsy since at least 500 BC.”(1) Interestingly enough, fasting has been used for thousands of years to heal the body. The father of modern medicine, Hippocrates wrote, “To eat when you are sick, is to feed your illness.”(4) “Modern medicine” seems to have shied far away from what Hippocrates believed and practiced. He believed the body could heal itself, that many illnesses were caused by our lifestyle and diet. Using natural methods to help patients, he believed fasting and the right kinds of food could be the medicine for people to get well.

Don’t get me wrong, modern medicine does great good; it has advanced our world and saved many lives. However, if we use pills and medications as a substitute for a healthy lifestyle, we are doing ourselves an injustice. We must do everything in our power to partner with how our bodies were made, while also realizing that illness and disease occur as a result of a fallen world. It is modern medicine and healthcare that can be agents for healing in times of disease.

With information so readily available, many people’s ideas, opinions and facts upon which they base their beliefs are primarily based on current trends. The benefit when looking back at history, especially at how humans survived for thousands of years, is we get to see the lasting effects of a particular practice. It is only then that we can get the full picture.

Most of us live in a time of abundance. We have access to food whenever we want to eat, however, this has not been the case for most of human history. In ancient times, humans would have to go out and kill their food. They would eat that kill for one, maybe two days, and then they might not eat for several days until they found another meal. They were forced to fast. Their bodies would store its excess nutrients so they could survive until their next meal. Today, most people hate that we store excess food as fat, but if our bodies didn’t store fat, humans would be extinct.

The storage of nutrients as fat has kept mankind alive for thousands of years. Fat storage is a good thing, except when we store so much fat that it interferes with our body’s functions. In a time of abundance, we must keep up this lifestyle of fasting that our ancestors have practiced for thousands of years in order to live in a balance. Since our bodies are made to help us survive in between meals, we must learn to tap into these complex mechanisms and use them to our advantage, especially in a time when the survivability component is essentially wiped out due to readily available food sources.

Key Takeaway: Fasting is not a new fad. It is a proven concept that has been around for thousands of years.

Current Evidence:

First, let me put your mind at ease. Most people can be skeptical about fasting because they think of it as starvation or that their bodies are going to go into starvation mode and ruin their metabolism. I thought the same thing before I did the research. We were all taught that eating 5-7 times a day was the best way to go when it comes to losing weight and having a fast metabolism. But interestingly enough, that mindset is relatively new and has only advanced as the obesity rate has gone up.

So just to be clear, I want to differentiate between starving ourselves and fasting. “Starvation is the involuntary absence of food. It is neither deliberate nor controlled. Starving people have no idea when and where their next meal will come from. Fasting, on the other hand, is the voluntary withholding of food for spiritual, health, or other reasons. It is the difference between suicide and dying of old age.”(4) I am not advocating for extreme dieting, weight loss, or eating disorders. I am simply presenting you with the research. Later, I will help you see how to fit fasting into your healthy lifestyle.

Obesity and Diabetes

Over the last 20-30 years, obesity has become a pandemic. “At least 2.8 million people die each year as a result of being overweight or obese and the prevalence of obesity has tripled from 1975 to 2016.”(8) Diabetes can be a huge part of the obesity pandemic. The real frustration is, both diabetes and obesity are almost always preventable. Could fasting help tackle the obesity and diabetes problem we have as a country?

First, let’s talk about insulin. Insulin insensitivity is the main cause of type 2 diabetes which is closely linked to obesity. When we eat, our bodies secrete a hormone called insulin that allows those nutrients, especially sugars, to get into our cells for energy use or storage. When we are constantly eating we will have elevated levels of insulin. Our body eventually loses sensitivity to insulin causing our blood sugar levels to be out of wack. “Fasting is the most efficient and consistent strategy to decrease insulin levels.”(5) “Contrary to popular belief, all foods raise insulin.”(5) Obviously, carbs raise insulin levels much higher, but the best answer to fixing our insulin problems is to not raise insulin at all. Hence fasting. “Regular fasting, in addition to lowering insulin levels, has also been shown to improve insulin sensitivity significantly. This is the missing link in the weight loss puzzle. Most diets reduce highly insulin-secreting foods but do not address the insulin resistance issue.”(5)

There is a state that our body goes into when we eat, called the “fed state.” Once we have digested all of the food, the energy is either used or put into storage for later; our body then goes into the “fasted state” after several hours which means our body has to start using the storages for fuel. Thus, our body primarily uses our body’s fat stores when in the fasted state.

Let me give you an example. Let’s say that I made a delicious, juicy steak last night to eat for lunch today that is readily available to me in my fridge. How much sense would it make for me to go to the store, buy another steak, come back home, trim, marinate, cook and then eat the steak when I already have one readily available to me in my house? That would be pretty dumb, right? It is the same for our bodies. When we eat, our body digests and absorbs the nutrients into our blood so they can be dispersed to where our body needs them most. When nutrients are in the blood they are readily available for our body to use. Why would our bodies burn stored fat (which requires more energy to be transformed into glucose) when there is already a readily available source of energy in our blood already? It doesn’t. Our bodies use up those storages primarily when we are in the fasted state. So when you eat every couple of hours, this causes us to always have glucose readily available and therefore our bodies become efficient at storing fat, but not burning fat.

The fact is, eating 5 times a day does not solve the insulin problem. Constantly eating throughout the day and before bed sets us up to store excess energy as fat. “In fact, nighttime eating is well associated with a higher risk of obesity, as well as diabetes.”(2) “This is mostly because insulin sensitivity decreases throughout the day and into the night.”(10) Constant eating is never a good thing. We must live in a balance.

Key takeaway: Fasting can be a huge asset in helping to combat obesity and diabetes.

Digestive Health and Circadian Rhythms

The digestive system is an amazingly complex system that breaks down the food that we eat, absorbs those nutrients into the bloodstream, and gets rid of the waste. Our digestive system is made of muscle. These muscles are very resilient, but they still need rest to recover and do their job efficiently. In addition to the muscles in the digestive system needing rest, the organs that secrete the enzymes that break down our food also need a break. If we are constantly eating, our organs like the pancreas, for example, must work tirelessly to keep up with the rate we are consuming food.

Millions of people suffer from some sort of digestive system issue. This is another key benefit that fasting brings to the table: when we give our digestive system a rest period, we allow it to recover which combats symptoms consistent with irritable bowel syndrome, etc. “Fasting appears to have a positive influence on gut health.”(10) Fasting also seems to have a better effect on weight loss and other issues even better than if we were to reduce our daily calories and eat every 2 hours. “In humans, intermittent-fasting interventions ameliorate obesity, insulin resistance, dyslipidemia, hypertension, and inflammation. Intermittent fasting seems to confer health benefits to a greater extent than can be attributed just to a reduction in caloric intake.”(3) Not only is it better for your gut to not eat constantly, but it also appears that fasting actually allows for greater results.

It may seem weird to group together digestive health with circadian rhythms, the correlation surprised me too. However there is a tremendous correlation between when we eat and our daily rhythms. “Feeding signals appear to be the dominant timing cue for the rhythms of peripheral clocks, including those that control metabolic pathways. Thus, consuming energy outside the normal feeding phase (i.e., late-night eating in humans) may reset some peripheral clocks and disrupt energy balance.”(10) Translation - when we eat directly affects our metabolism and our body’s rhythms. If our body’s rhythms are off, we will not function efficiently and optimally. “Taken together, the data strongly suggests that the timing of food intake is an important determinant of human health and disease risk.”(10)

Key Takeaway: Fasting can have a huge impact on digestive health which will impact our body’s natural rhythm.

Immune support and Inflammation

Ever been told that you need to eat to keep your energy levels up when you are sick? When you really think about this idea, it doesn’t seem to line up with current evidence. When we are sick, our body is diverting most of our energy to our immune support via the sympathetic nervous system (SNS). This takes a lot of energy. When we eat, digestion requires a lot of energy via the parasympathetic nervous system (PNS). These can conflict with each other because the sympathetic nervous system can inhibit tissues that are stimulated by the parasympathetic nervous system and vice versa. For example, have you ever eaten a big meal and then exercised right after? That food seems to sit in your stomach like a rock. This is because the digestive system is stimulated by PNS and our skeletal muscles are stimulated by the SNS. The SNS takes precedence in a lot of situations because it also aids in our fight or flight response which uses skeletal muscles. When we start to use our skeletal muscles, our body takes blood flow and energy away from our digestive system and diverts it to our skeletal muscles for use. This is similar to our immune support. These systems can conflict with each other. If we eat a big meal it can take blood flow and energy away from our immune response, which is not what we want when we’re fighting an infection.

This is why Hippocrates wrote, “To eat when you are sick, is to feed your illness.”(4) Our bodies need to have all their energy focused on getting better, not digesting food. Another well-known quote from Hippocrates is “Humans, like most animals, do not eat when they become sick. For this reason, fasting has been called the ‘physician within’.”(4) This is an interesting concept to consider. There are no other animals who, when they get sick, go and eat a big meal. They tend to seclude themselves and rest. “Fasting is evolutionarily embedded within our physiology, triggering several essential cellular functions.”(2) It is our body’s natural response to fend off sickness and repair tissue. When we partner fasting with eating a diet full of nutrients, we will have a defense system that can withstand most illnesses.

Fasting is our body’s defense system. “During fasting, cells activate pathways that enhance intrinsic defenses against oxidative and metabolic stress and those that remove or repair damaged molecules.”(3) This can help with not only immune support but inflammation as well. Inflammation is often caused by stressors in our bodies; this could be the food we eat, how we move, or our stress level. “Cells respond to intermittent fasting by engaging in a coordinated adaptive stress response that leads to increased expression of antioxidant defenses, DNA repair, protein quality control, mitochondrial biogenesis and autophagy, and down-regulation of inflammation.”(3) Fasting allows our body to repair itself! It can be a great asset to us regarding our body’s defense systems.

Key Takeaway: Fasting can be a huge asset to our body’s defense mechanisms.

Performance, Metabolism, and Muscle Preservation

Fasting seems to be a great solution for weight loss and obesity, but what are its effects on our metabolism and exercise performance? Many are worried about their metabolism tanking or losing muscle mass if they start to implement fasting into their lifestyle. It is actually amazing how fasting impacts our performance and metabolism for the better. “In essence, fasting transitions the body from burning sugar to burning fat. Resting metabolism is NOT decreased but instead increased.”(5) One big reason for this change is because of hormone regulation. Fasting allows the body to balance its hormones. “Fasting actually increases HGH (Human Growth Hormone) to stimulate our metabolic processes and protect our lean body mass.”(6) This could actually help us gain lean muscle tissue and balance our often, unbalanced hormones.

Many equate fasting with starvation, which will eventually begin to burn muscle tissue for energy. This is not what happens in intermittent fasting. I love this analogy that Dr. Jason Fung gives as to the idea that our bodies will burn muscle instead of fat: “It’s as if you store firewood for a wood-burning oven. You pack lots of firewood away in your storage unit. In fact, you have so much, it is spilling out all over your house and you don’t even have enough room for all the wood you’ve stored. But when the time comes to start up the oven, you immediately chop up your sofa and throw that into the oven. Pretty stupid right? Why would we assume our body is also so stupid? The logical thing to do is to start burning the stored wood. In the case of the body, we start to burn the stored food (fat stores) instead of burning precious muscle.”(6) I love that his approach to the body is not only evidence-based but also common sense based. Our bodies are an amazing creation. One that has survived for thousands of years under extreme circumstances. The body does not ‘burn muscle’ in an effort to feed itself until all the fat stores are used.(5) This is why the body stored fat in the first place.

But what about athletic performance? First, this can depend on the type of fast you partake in. If it is a fast for several days, your performance may suffer some because you are not used to having fasted that long. But intermittent fasting is a great way to keep a balance, while still being able to perform athletically. Also, note that many attribute fatigue and a drop in performance because they eat less during the days they do intermittent fasting. This is mostly due to the lack of energy they consume.

When one first starts fasting on a regular basis, their performance may decline slightly. But as you are accustomed to exercising in the fasted state, your body becomes efficient at burning fat for energy. Hormonally, fasting can aid in energy production and muscle building?. “Over a five-day fasting period growth hormone secretion more than doubled.”(5) Growth hormone is key in muscle preservation and building. This could help immensely in the building of muscle if the fast is done at the right times. The real key here is to fast for your goals, so for most of us simply trying to maintain a healthy lifestyle of gaining lean muscle, intermittent fasting can help us do that, if we practice it on a regular basis. If you are one that has a hard time gaining weight and may even be underweight, fasting is not necessarily the way to gain the amount of body weight you need. But if you are trying to lose fat while maintaining muscle, fasting could be perfect. We will talk further about how to fast for your goals and lifestyle.

Key Takeaway: Fasting seems to have a positive effect on metabolism and muscle preservation. In addition, fasting can be a great tool to use to reach our goals.


What effect does fasting have on our cognitive abilities and focus? Well, have you ever eaten a big lunch and then tried to get some work done right after? If you like most of us, its easier to nap afterwards than be productive. Like we have talked about previously, the digestive system demands an enormous amount of blood flow and energy to break down our food. It diverts this energy away from other areas in the body in order to function efficiently. We tend to lose focus after a meal because our body diverts energy away from our brain and down to the digestive system. Fasting can enable us to have a better focus by allowing us to divert all of the blood flow we need to our brain. This is one main effector of cognitive ability that I use fasting to help me with daily.

“Dr. Geyelin was the first to document the cognitive improvement that could occur with fasting.”(1) People have been noting for many years that fasting could have a positive effect on brain function. The body’s level of focus and cognitive ability is greatly affected by what we eat. You will likely feel more energized and alert after a lunch of chicken breast and veggies rather than mac n’ cheese with a soda. The real impact of fasting is when we partner fasting with a clean diet.

Key takeaway: Fasting can have a great impact on brain function and focus.