Eating is one of the first things we think about when we wake up in the morning and something that continues to be on our mind throughout the day. If it’s not because of hunger, it’s out of habit. The temptation to eat constantly surrounds us, with delicious treats in our coffee shops, junk food in our convenience stores and a sea of restaurants that fill up our city blocks. The typical American averages as much as 3,600 calories per day, spaced out between 3-5 meals, with snacks in-between. Not to mention that ninety percent of social activities revolve around food. Nonetheless, interest has grown in recent years around intermittent fasting, which Harvard explains is “an eating schedule that is designed to expand the amount of time your body experiences a fasted state.”  Nearly half a million people search the term “intermittent fasting” on Google every month. There is a ton of curiosity about the health benefits, which also appear to have little-to-no downside. Spacing out food? We could be down with that.  Not eating for 12 to 16 hours? No biggie. But going without food COMPLETELY? That sounds a bit crazy. In this sense, what is traditionally known as water fasting would appear to be dangerous. Especially if you haven’t done it before, you might worry about how your body would react to food deprivation. Besides, why would someone do water fasting anyway? Isn’t it clear that the body was designed to need food? It’s natural to assume that water fasting would severely weaken the body. This is where the conversation gets interesting. Doctors have been investigating the science of fasting for nearly 70 years and the research extends across multiple different countries. The results are so shocking – jaw-dropping even – yet somehow so few of us know about these discoveries. Dr. Andreas Michalsen of the Charité Hospital in Berlin, puts it this way: “If I had been studying a new drug, and got these results, I would certainly be getting calls everyday with proposals, financial aid and money for research.” So what exactly are these discoveries? Let’s explore together.



One could argue that the original scientific discoveries behind fasting happened by accident. The year was 1948. Psychiatrist Yuri Nikolayev was working in a Moscow hospital with mentally ill patients. There was one patient that was diagnosed with schizophrenia who was particularly troublesome. He was prostrate and mute, and refused to eat. But rather than force the man to eat, as would be the protocol, Dr. Nikolayev decided to let the man deprive himself of food. Dr. Nikolayeu had already been interested in the topic of fasting, after reading the 1911 book by Upton Sinclair The Fasting Cure, which was a flagship book on therapeutic fasting. Nikolayeu’s colleague had also recently suggested to Soviet medical authorities that they experiment with fasting treatments, to which he was turned down. The idea that not eating could cure anything seemed laughable at best. Nonetheless, Nikolayeu went ahead and let his schizophrenic patient go without food. And the results were nothing short of stunning.  In his journal, the psychiatrist recounted, “from the fifth day, his negativity began to decrease and the patient opened his eyes. On the tenth day, he started to walk, but still didn’t speak. On the fifteenth day, he drank a glass of apple juice left on his nightstand, then he went for a walk and began to return to social life.” The man eventually fully recovered, and the case was one of a kind. Nikolayeu was perplexed by the results. Fast forward 15 years, and Nikolyaeu continued to experiment with water fasting. Over the course of time he treated patients with schizophrenia, depression, obsessive tendencies and phobias. Usually, they would fast for a period of 25 to 30 days, with some as much as 40 days. He was not without critics. As his son Valentin Jurevich recounts: “The doctors were opposed to fasting, because they did not understand the essence of it. People usually think of being hungry as something bad. You need to turn your head back to front to accept the idea that fasting can cure. And it’s even more difficult for a doctor than an ordinary person.” The criticism compelled Yuri to undergo a comprehensive research program, where he studied fasting with rigorous measures including physiological tests, hormonal parameters and biochemical tests. Different markers were analyzed both during and after fasting. Hundreds of patients participated. Ultimately, Dr. Nikolayeu and his team found that there was a clear correlation between changes in the body and the improvement of the patient. He recounted, ”Fasting has an impact not only on mental illness, but also the entire personality.”  In his career, Yuri treated over 8,000 patients with fasting, to which 70% of them experienced a significant improvement. Depending on their lifestyle choices and eating habits, 47% had maintained that improvement six years later.  Despite the government originally being skeptical, they later confirmed his results and since 1998, therapeutic fasting has been officially recognized by Russia. Yuri’s work extended beyond his death, and since 1998, the Goryachinsk Sanatorium has treated over 10,000 patients, which is located right off the coast of Lake Baikal in Russia.  Diseases they have treated include diabetes, rheumatism, asthma, hypertension, allergies and more. Nearly two-thirds saw their symptoms disappear after one or more courses of fasting. Dr. Natalia Bataeva, who works at the center, adds “Very often we get people who have been in the hospital. They’ve had the best clinical examinations, but nothing helped.” The discoveries around fasting extend far beyond Russia, and at the Buchinger Clinic in Berlin, they have 2,000 people stay there every year for therapeutic fasting treatment. Buchinger has also opened a clinic in Marbella, Spain  One patient who was in poor health and had an enlarged liver recounted, “Personally, I couldn’t imagine being able to fast. It seemed impossible for me to not eat anything for three weeks.” Nonetheless, he went forward with it. And after the first treatment, his liver shrank back to normal size and his blood tests also normalized. In 2016, the Buchinger Clinic published their findings from a large study that showed a remarkable 84% improvement in health during fasting for patients that had serious conditions. Most recently, Dr. Valter Longo, the Director of the Longevity Institute at USC, studied the effects that fasting can have on cancer. These results might just make your jaw drop all the way down to the floor. Longo had a theory that fasting might provide protection against toxins in the body. First using mice as an experiment, he found that when we fast our “good cells” go into protective mode because we are not receiving an external supply of nutrients and glucose. However, fasting DOES NOT protect the cancer cells, meaning that fasting actually makes cancer cells weaker. This has changed some of the narrative around chemotherapy. For many patients, the decision has been framed as two extremes: suffer at the hands of cancer, or suffer at the hands of chemo as a means of getting rid of it. Now there is an alternative option.  Even without chemotherapy, the research suggests that fasting ALONE can aid the death of cancer cells or reduce their growth.  Nora Quinn, who lives in Los Angeles, attributes winning the battle with her breast cancer to fasting. She had five chemotherapy sessions. In the three that she fasted beforehand, she fared significantly better than the times she did not fast before.



At this point, you might be wondering why you haven’t heard any of this before. A highly effective natural treatment – and in some cases, a cure – to chronic diseases, mental health issues and even cancer. This should be national news, and dollar bills should be raining down on this research field. It’s not hard to imagine that if these types of results were delivered in clinical trials of a brand new pharmaceutical drug, the amount of publicity, funding and attention would be off-the-rails. As Dr. Longo recalls in Sylvie Gilman’s Science of Fasting documentary, “I recently presented to one of the largest pharmaceutical companies in the world and I challenged the executives of the company to come up with a cocktail of drugs, not just a single drug, but a cocktail of drugs that would have a more potent effect than fasting has.” At the root of this problem is the reality that our healthcare model encourages companies to see disease as a marketing opportunity. When people get sick, it means that pharmaceutical companies get paid. Dr. Francoise Wilhelmi de Toledo, the director of the Buchinger Clinic explains, “Today there is an extraordinarily lucrative market for the treatment of disease, especially chronic diseases. When a diabetic becomes chronic, that is an opening to sell medication for several decades or do operations.” When it comes to natural treatments or finding cures, it is not so simple. There are multiple interests at play. What benefit is there to pharmaceutical companies when we use fasting as a treatment? None.  Even when it comes to actually finding cures, if a pharmaceutical company were to develop a miracle drug for cancer, it wouldn’t necessarily be beneficial to them. If curing cancer was a one-and-done, there would not be the repeat sales that you get with chronic illness. It is most profitable when you can develop drugs that keep people just sick enough, while reducing their symptoms and making them dependent on your product for life. This isn’t speculation, by the way. This was the same strategy that Purdue Pharma employed with the opioid crisis, as seen in the 2021 Emmy-award winning mini-series Dopesick. Despite the interests of Big Pharma, and whatever ways politicians might be in bed with them, public outcry can still go a long way to creating change. The more public this information becomes, the more it will force the hand of the United States government. In Germany, things have already started to change. In Berlin, Charité Hospital has an entire floor dedicated to fasting and a dozen other public hospitals do the same. Social security payments are supplied to patients to cover the costs. They have accepted – and embraced – that the scientific research is not speculative, not in the slightest. The effects of fasting are observable, measurable and clear.


As Russian doctor Alexey Kokosov explains, when we start fasting it “causes a state of stress” in our bodies. This activates what is known as cytogenesis, which is the formation and development of cells. Recovery mechanisms and auto regulatory processes, which are usually inactive because of our constant consumption, start turning on. However, the first few days of water fasting can be really rough. The body starts the process of elimination and detoxification, cleansing itself. For some people, this can lead to nasty symptoms like severe pain or intense migraine headaches. In this state of stress, the acidity in the blood often increases, leading to what is called a crisis of acidosis. As the body changes its “mode” of nutrition, this is a natural part of the process. Urine analysis has been able to track peak acidity levels and observe when they level off.  While the first few days are painful, it’s all critical to the healing process. After the third day, the patient's symptoms generally improve.  So how exactly does the body survive on no food? The body has three “fuels” which are glucose, fats (lipids), and proteins. Our most essential source of fuel is glucose, which is necessary for our basic functioning. The brain cannot do without it. But after the first day of fasting, our glucose supply is completely exhausted. At this point, the body temporarily converts protein into glucose. It then quickly cuts back on its use of protein, and draws on reserves of fat to act as a substitute for glucose. This fasting fuel is known as ketone bodies, which become the main food supply to the brain. As odd as this sounds, the body is essentially eating itself. It’s working off excess reserves as it settles into a new equilibrium. But even as the body adapts, you might find that your mind doesn’t always follow. A psychological hunger ensues, as we imagine food.  Similar to how we could want a bowl of ice cream even when we’re not actually hungry, this form of psychological hunger can make us feel like we have needs that we don’t actually have. As discussed, the body is already taken care of as it feeds on its own reserves. Once we push past this state of psychological hunger, many people often report feeling a sense of euphoria. The senses sharpen. One of the Russian patients described it as a sense of “freedom”. With all the toxins having been released out of their body, some have noticed how that impacts them physically, saying that their skin became “radiant”. Scientists have been able to identify three different “effects” that happen during fasting – a stimulant effect, an antidepressant effect and a sedative effect.  Dr. Valery Gurich, who worked under Dr. Nikolayeu in Russia, explains that, “fasting has a stimulant and antidepressant effect. The stimulant effect takes place during the first week of fasting and antidepressant effect during the first week of starting to eat again. The third type of effect is a calming sedative effect. It can be observed after the crisis of acidosis.” The ultimate result? "The body [gets] rid of the parts of the system that might be damaged or old, the inefficient parts, during the fasting. Now, if you start with a system heavily damaged by chemotherapy or aging, fasting cycles can generate literally a new immune system," Longo said in a publication for USC, his current school of residence.  All of these things have been observed, rigorously analyzed and repeatedly confirmed by many studies around the world. Still, you might be wondering, how long can fasting last? Surely… we need food at some point. Is there a breaking point to the transformative and somewhat miraculous health benefits?


For obvious ethical reasons, scientists did not try to test the limits of fasting through humans first. Instead, they looked at wildlife. There are some animals, like the male emperor penguin that are “natural” fasters. Scientists have studied them and found they were able to go 100 days before they must eat again. In subsequent studies on rats, there were similar results. The world record for humans is Angus Barbieri, a 456 pound man who fasted for 382 days and lost 276 pounds in the process. Yes… that’s over a year. Circling back to the science of fasting, Barbieri’s enormous amount of fat reserves made this impossible task possible.  But since most of us don’t weigh 400+ pounds, we don't have that kind of fat storage to deplete. Curiously enough, 40 days is the breaking point of most humans. "Generally, it appears as though humans can survive without any food for 30-40 days, as long as they are properly hydrated. Severe symptoms of starvation begin around 35-40 days," said Dr. Peter Janiszewski, a researcher for the Public Library of Science.  More specifically, scientists have been able to calculate that the average adult who is 5”5, weighs 154 pounds and has 15 kilos of fat reserves is enough for a healthy person to keep going for 40 days.


If this all sounds somewhat familiar, that’s because it is. Jesus famously fasted for 40 days and 40 nights. How is it possible that in a pre-scientific age that Jesus would know to fast for exactly the amount of time the average person can go before starving? It’s a curious correlation that some would chalk up to Jesus’s divinity. Wherever you stand on that, the reality is that the Bible has some of the most extensive literature on fasting throughout human history. Long before these scientific discoveries, fasting was mentioned 70 times in the Bible from Genesis through Revelation. Perhaps not so coincidentally, the Bible teaches that the same thing is happening spiritually that is demonstrated physically. Things that were broken in our spirits are now being repaired as we use our time of fasting to focus on God. Junk that didn’t need to be there is slowly starting to fall off. Instead of constantly indulging in food, we take steps towards developing the skill of self-control. Just as our senses start to sharpen physically and mentally, our sense of God starts to sharpen spiritually.  Author John Mark Comer explains, “It helps us to discern his voice through the noise and distraction of our lives.” Fasting was also a means of standing in solidarity with the poor. We read in Isaiah 58: "This is the kind of fast day I’m after: to break the chains of injustice, get rid of exploitation in the workplace, free the oppressed, cancel debts."  This was estimated to have been written around 700 B.C., meaning this is almost a 3,000 year old text advocating for something we'd consider along the lines of "social justice" in today's world. In the book of Daniel, we see Daniel undergo his famous 21 day fast. After 10 days, the mental and physical benefits of the fast are observed. We read, “they looked healthier and better nourished than any of the young men who ate the royal food." (Daniel 1:15-16 NIV).  This type of comparison sounds like an observation that would come from the modern studies of scientists. Ultimately we find that together, science and scripture paint a beautifully harmonious picture of the enormous physical, mental and spiritual benefits of fasting. 


At this point, it’s hard not to be inspired and motivated by all of the extensive data we’ve covered on fasting. For many, it brings excitement to the experience of trying fasting for the first time. We’ve learned that fasting is not dangerous. In fact, it makes a ton of sense when you consider that for most of human history, food was a scarcity. For the first time in human history, we live in a time of plenty. Ironically, it is when we eat constantly and don’t fast at all that we experience the most difficulties with our bodies. This means that the body is better equipped to deal with a lack of food rather than an excess of food.  However, this doesn’t mean we should just simply start tomorrow. The safest, most effective periods of fasting are intentional, well-planned out and consider a person’s bio individuality. This term was first coined by Joshua Rosenthal, founder of the Institute for Integrative Nutrition in New York. He explains that each person is a unique individual with highly individualized nutritional requirements.” This is critical to understand as you prepare for your fast. Your starting point might not be the starting point of another person. When it comes to fasting, we have to caution against a “one-size-fits-all” approach. The intensity of the pain during the first three days could be different. You may have pre-existing conditions that make fasting more or less difficult. With that in mind, here’s some things to consider.

Starting small

Similar to how someone would prepare for a marathon, some prefer to build their endurance over time with fasting. This might mean initially starting with a one-day fast, which still has great benefits. From there, the next time you try fasting you do a three-day fast. After that, maybe you try a seven-day fast and work your way up eventually to a 30 to 40 day fast. It’s important to note though, that not everyone needs to do really long fasts to reap the health benefits.

Considering a clinic

Some would recommend working with medical professionals that can monitor you if you are going to do longer fasts.  You can start by investigating if there is a clinic or medical center that specializes in fasting near your city or town. Otherwise, this is why some fly to places like the Buchinger Clinic in Berlin for anywhere from ten days to four weeks (if you have the funds of course). These stays act more like a health getaway or retreat. Clinics often employ the following treatments to help patients better cope with fasting, especially in the first few days. They include:
    • Body wraps
    • Massage
    • Saunas 
    • Two or three hours of exercise daily 
 All of these treatments have the same goal in mind: to stimulate and help aid the organs of elimination. These organs include the kidneys, intestines, liver, lungs and skin.

The Fast Mimicking Diet

Aimed at reaping all the benefits of water fasting, but without the negative side effects in the first few days, Dr. Longo developed the Fast Mimicking Diet (FMD).  The FMD was the central focus of his bestselling book the Longevity Diet. On the first day, this might mean cutting your intake to just 1,000 calories. For the following four days, you whittle it down even more to 500 calories or less. Essentially, it kind of “hacks” our system by eating a very small amount of calories per day. Longo explains, “Your body…does not recognize that it is being fed. This causes the body to enter a fasting mode.” Because you are still eating small amounts of food, some have found this to be less psychologically and physically taxing. In terms of how often to do the FMD, Dr. Longo recommends those who are overweight or obese to practice this once a month.  If you're average-weight but have risk factors for diabetes, cancer, or cardiovascular, or neurodegenerative diseases, he recommends undertaking this every two or three months. If you're considered a healthy weight but are not active, this is recommended every four months. And if you are a healthy weight and partake in a healthy diet / routine exercise, you're only advised to do this twice a year (every six months).

Integrating a spiritual component

For maximum benefit, you can also integrate a spiritual component to your fasting regimen. Practicing the Way has developed a fasting guide specifically for those who want to model the spiritual practices of Jesus. They break up the fast into four weeks, with a core focus for each week. This may help with “starting slow” as we mentioned above. For one day a week every week, you start to integrate fasting into your schedule. What they call “reach exercises” include fasting for two days a week, and then working your way up to longer fasts over time. They also propose serving with the poor on the day you fast to stand in solidarity with the impoverished.

Universal tips

However you approach fasting, there are some universal principles. Make sure you stay hydrated with water at all times. If you are taking any kind of medications consult with your doctor first. Additionally, avoid overcompensating for your fasting period. Meaning when you start eating again, do not go on a binge. If you initially give your body a rest from eating but then immediately eat a ton of food to "make up for lost time," you may gain more weight over time and put pressure on your body's digestive system.  So once you break your fast, wade slowly back into the waters of eating, starting with small portions of nutritious food.


Dr. Longo notes several categories of people who shouldn't fast for various health reasons. His list includes: 
  • Pregnant women
  • Severely underweight individuals
  • Those over the age of 70 (unless they have a doctor's approval)
  • Those with liver or kidney diseases
  • Those with various pathologies
  • Those who take medication (unless they have a doctor's approval),
  • Those with low blood pressure
  • Anyone training for intense athletic competition
 There are specific reasons and caveats related to each of these people groups that are worth investigating. Some have workarounds, hence working with a doctor to find a solution. Additionally, if you’re currently struggling with an eating disorder, fasting is not recommended.


The biggest shame in the science of fasting is that there hasn’t been billions of dollars of funding pouring into this field.  While fasting shouldn’t be considered a cure-all for every disease or mental health struggle, it simply has not received enough funding to know how far its benefits extend. We must further flesh out the direct correlations and benefits between specific diseases and fasting. For example, emerging research suggests that fasting could help prevent or treat other maladies like Alzheimer's disease, Crohn’s disease or autoimmune diseases (such as Multiple Sclerosis).  Multiple Sclerosis (MS) is an autoimmune disease in which nerve damage hampers communication between our brains and our bodies. Most recently, actress Christina Applegate has gotten a ton of media attention because of her diagnosis. She told Vanity Fair, “with the disease of MS, it’s never a good day. You just have little shitty days. Getting in the shower is frightening. You can fall, you can slip, your legs can buckle. There are just certain things that people take for granted in their lives that I took for granted. Going down the stairs, carrying things—you can’t do that anymore. It fucking sucks.” In one of Longo's studies done examining the effects of fasting and MS in mice, he found: "Cycles of the FMD not only reduced the severity of multiple sclerosis (MS) in mice; it eliminated all symptoms in a portion of the mice that already developed the disease…three cycles eliminated disease symptoms in 20 percent of the mice. FMD worked in another remarkable way: it promoted regeneration of the damaged myelin in the mouse spinal cord.” It isn't just Longo and his research team pushing these findings.  A few years ago, a team of researchers from Mt. Sinai Hospital in NYC published a study around fasting in the scientific journal Cell. The study observed the role of monocytes, a type of white blood cell produced by your body. High monocyte levels are often linked with autoimmune diseases. Here's what they found: "Short-term fasting reduced monocyte metabolic and inflammatory activity and drastically reduced the number of circulating monocytes."  However, we won’t know the full extent of these benefits unless the field of fasting gets much more funding.  Dr. Longo himself hopes to receive a grant from the U.S National Cancer institutes to run a clinical trial in 11 hospitals across the country to continue the research of his fasting-mimicking diet (FMD) and chemotherapy treatments for breast cancer. It is an injustice that there isn’t more attention paid to this research, especially to people who are suffering like Applegate. As Dr. Andreas Michalsen of the Charité Hospital in Berlin puts it, “people just say, “mhmm.. that’s interesting”, but there is no real encouragement for the research. It has to change.” For more on nutrition, visit our Nutrition Hub here.


Your journey with food is unique, so you deserve to be uniquely served. These fields help us better understand how to help you with your nutrition journey.

*Your data is covered through our privacy policy.