Dry fasting according to Filonov: how it is carried out and the risks

Dry fasting involves completely abstaining from both food and liquid for a specified period. The dry fasting method, described by Sergei Filonov in his books and popularized in Russia and abroad, promises "deep cleansing," a "reset" of metabolism, and the treatment of a wide range of diseases, from obesity to chronic inflammatory and autoimmune conditions.

It's important to understand that dry fasting is fundamentally different from traditional therapeutic water fasting and gentle intermittent fasting regimens. During traditional therapeutic fasting, water is allowed, and the body loses energy but maintains blood volume and the ability to eliminate waste products through urine. During dry fasting, the body simultaneously experiences both an energy deficit and increasing dehydration, which dramatically increases the strain on the heart, blood vessels, and kidneys. [1]

Proponents of Filonov's method claim that dry fasting "triggers powerful autophagy," activates anti-tumor defenses, "rejuvenates" the body, cleanses it of waste and toxins, and supposedly allows for the treatment of severe chronic diseases. These promises are widely promoted in books, blogs, and specialized websites, but are based primarily on the author's observational experience and patient testimonials, rather than large, controlled studies. [2]

Current scientific data on fasting generally focuses primarily on short-term water fasting and various intermittent fasting regimens where water is not restricted. Dry fasting as a therapeutic method has been virtually unstudied in large randomized trials. Clinical guidelines for the treatment of obesity, diabetes, cardiovascular disease, or cancer do not list dry fasting as an acceptable therapeutic method. On the contrary, professional guidelines emphasize the dangers of prolonged dehydration and the need to limit even forced periods of fasting before surgery. [3]

The purpose of this revised article is to provide an honest and detailed analysis of Filonov's dry fasting method from the perspective of modern evidence-based medicine. It will examine the promised effects, the physiological mechanisms actually studied, research data on short-term dry fasting, as well as the risks, contraindications, and safe alternatives for weight loss and improved metabolism. This information is intended to inform informed decision-making: experimenting with such practices without consulting a doctor is unsafe and, in some cases, can be life-threatening. [4]

Table 1. The main promises of dry therapeutic fasting according to Filonov and what science says

Promise of supporters	As it is described in popular literature	What is known from research data
"Complete body cleansing"	It is claimed that without water the body “burns toxins” and “removes waste.”	There is no scientific term for "toxins"; the primary detoxification system is the liver and kidneys, which, on the contrary, need water to function properly.
"Potent autophagy and antitumor effect"	Activation of a “unique mode” of cellular self-cleansing is claimed.	Autophagy is indeed activated by calorie deficit, but there is no direct clinical evidence of the antitumor effect of dry fasting in humans.
"Obesity Treatment and Weight Management"	They promise quick weight loss and no weight return.	Weight loss occurs with any strict fast, but without lifestyle changes, the weight usually returns; prolonged dehydration increases the risk of heart and kidney damage.
Strengthening the immune system	The method is positioned as a way to “reboot” the immune system.	Brief fasting may have a mild effect on inflammatory markers, but there is no evidence of benefit for extreme, multi-day water deprivation, and the risks are significantly higher.
"A universal method for treating many diseases"	The therapeutic effect is claimed for a very wide range of diseases.	Current clinical guidelines do not include dry fasting in treatment regimens for any disease; on the contrary, they emphasize the risks of dehydration.

How is Filonov's method described and what is alarming about it?

Sergei Filonov, a physician by training, is the author of several popular books on dry therapeutic fasting. His biography emphasizes his interest in the body's "hidden reserves" and his own experience with long periods of complete abstinence from food and water. Based on this experience and his practice with patients, he developed a so-called fractional dry fasting regimen, which he describes as more "gentle and manageable" than a single, long course. avalonlibrary.net

Fractional dry fasting, according to the author's own descriptions, is built around several successive cycles of complete abstinence from food and liquid, separated by periods of "restorative nutrition." The original article on the portal and in books mentions fractions lasting about a week or more, with increasing duration, resulting in a multi-day or even multi-week period of repeated dehydration. Even without providing precise protocols, it's clear that these are durations that significantly exceed what is considered relatively safe, even for water fasting.

Preparatory "cleansing" procedures occupy a special place in the methodology. Filonov's books describe home-based regimens for cleansing the intestines and liver, the use of herbal infusions, and exposure to mountain climates as supposedly mandatory steps before entering into a prolonged dry fast. These practices are not included in standard medical recommendations and lack convincing evidence for their impact on disease outcomes or safety when combined with extreme fasting. [5]

It's important to understand that the primary sources of information about Filonov's method are his own books, popular brochures, paid courses, and patient reviews collected by the author or his followers. English-language resources dedicated to dry fasting also emphasize that the method is based on personal clinical experience, not large-scale controlled studies. Independent publications in peer-reviewed medical journals confirming the safety and effectiveness of multi-day dry therapeutic fasting using this method are virtually nonexistent in open databases. [6]

Another concerning aspect is the method's positioning as a universal solution for a wide range of conditions, from excess weight to cancer and autoimmune diseases. Modern clinical guidelines in gastroenterology, cardiology, endocrinology, and oncology do not mention dry fasting as a therapeutic method, while nutritional recommendations increasingly focus on reducing unnecessary periods of fasting and dehydration, such as before surgery. This means that the proposed regimen falls outside the realm of standard medicine and is viewed by the professional community as a high-risk experiment. [7]

Table 2. Key elements of Filonov's methodology and comments from the standpoint of evidence-based medicine

Element of the methodology	As described by supporters	Medical commentary
A complete refusal of food and water for several days	"Deep cleansing", "switching to endogenous nutrition".	Long-term dehydration leads to a decrease in circulating blood volume, stress on the heart and kidneys, and the risk of acute renal failure and heart rhythm disturbances.
Factional nature of the course	Several consecutive cycles of dry fasting, separated by “rest”.	Repeated episodes of dehydration may cumulatively increase organ damage; there are no studies on the safety of such regimens.
Preparatory "cleansing" of the intestines and liver	They are positioned as the key to successful and safe fasting.	There is no clinical evidence of the benefits of these procedures; excessive cleansing may, on the contrary, worsen electrolyte balance and the condition of the mucous membranes.
Treatment of a wide range of diseases	The method is presented as a universal remedy for many diagnoses.	There are no universal treatment methods; specific evidence-based treatment regimens have been developed for most diseases.
Mandatory stay "in nature"	Considered important for the success of the course.	Being outdoors is beneficial in itself, but it does not offset the risks of severe dehydration and hunger.

What happens in the body during hunger and dehydration?

During normal short-term fasting without water restriction, the body first depletes glycogen stores in the liver and muscles, then lipolysis (the breakdown of fats) is activated, and ketone body levels increase. This is a natural adaptive response that allows internal energy reserves to be used temporarily. Water remains available, blood volume is maintained, metabolic waste products are eliminated, and the kidneys and liver continue to perform their detoxifying functions. [8]

When a calorie deficit is combined with a water deficit, the situation changes radically. Dehydration leads to a decrease in plasma volume, thickening of the blood, and an increase in its viscosity. The heart must work harder to push the thicker blood through the vessels. At the same time, perfusion of vital organs—primarily the kidneys and brain—is reduced, increasing the risk of acute renal failure, arrhythmia, dizziness, loss of consciousness, and stroke. [9]

Water is essential for maintaining a normal balance of electrolytes—sodium, potassium, calcium, and other ions responsible for the functioning of nerve and muscle tissue. When dehydrated, electrolyte concentrations in the blood can increase or, paradoxically, decrease with subsequent attempts to "rehydrate," leading to seizures, abnormal heart rhythms, confusion, and even coma. These conditions are known as hypernatremia and hyponatremia and require immediate medical attention. [10]

Dry fasting also increases metabolic stress. The body simultaneously experiences a deficit of glucose, fat reserves, and fluid, leading to a significant increase in ketone body concentrations and changes in the blood's acid-base balance. Water fasting can also be accompanied by ketoacidosis, but the availability of water facilitates the kidneys' work of removing excess acids and maintaining balance. In the complete absence of water, the body's compensatory capacity is severely limited, increasing the risk of severe metabolic disorders. [11]

Current clinical guidelines for preoperative fasting clearly demonstrate the position of evidence-based medicine: patients are allowed to drink clear liquids for up to two hours before a planned surgery, and for some procedures, an even more liberal regimen is discussed. The goal is to prevent dehydration and unnecessary stress on the body. Therefore, even in cases where fasting before a procedure is necessary, doctors strive to maintain access to water as much as possible, rather than deprive it. [12]

Table 3. Comparison of the main types of fasting

Characteristic	Short-term therapeutic water fasting	Dry therapeutic fasting	Daytime religious fasting with abstinence from water during the day
Food	Complete refusal of food	Complete refusal of food	Refusal to eat during the day, eating in the evening and before dawn
Water	Allowed in unlimited or controlled quantities	Complete abstinence from any liquid	Prohibited during the day, but free drinking at night
Duration of a single period without water	No, water is available.	A period of several days without water	Usually 12-16 hours, then restoration of water balance at night
Level of study	There are limited data from medical observation.	Very little data; mostly descriptions of proprietary methods	There are quite a lot of studies concerning healthy people and specific groups of patients
Position of recommendations	Allowed in select centers under supervision	Not included in clinical guidelines	Generally considered safe for healthy individuals when restrictions are followed

What research on dry fasting and religious fasting shows

The majority of published scientific papers on dry fasting are not related to proprietary treatment regimens, but to religious practices. Studies of Muslim fasting during the month of Ramadan and fasting among followers of the Baha'i faith show that daytime abstinence from water and food followed by evening replenishment of nutrition in most healthy individuals does not lead to serious disruptions in water balance and can be accompanied by moderate weight loss and slight improvements in metabolic parameters. [13]

The key difference between these regimens is that each day of fasting is strictly limited in time, while at night the person drinks water and eats freely. The total daily fluid requirement is usually eventually met, especially if the fast is observed during cooler months and with moderate physical activity. The body's metabolic and hormonal systems have time to partially recover between daily periods of abstinence. [14]

Some studies have noted a reduction in certain inflammatory markers and improvement in several lipid metabolism indicators following a daytime dry fast in overweight individuals with metabolic syndrome. However, these studies include a small number of participants, have a limited follow-up period, and do not assess long-term outcomes such as cardiovascular events or mortality. Therefore, extrapolating their results to extreme, multi-day dry fasting regimens is inappropriate. [15]

Some studies of five days of complete food and water deprivation under strict medical supervision, sometimes cited by proponents of dry fasting, show that even with this approach, the risk of combined hypovolemia, hypertension, and hypoglycemia remains very high. The study emphasizes that healthy volunteers did not experience any serious complications, but the participants were under constant observation, and their safe tolerance is explained by a powerful compensatory response, which may be significantly weaker in people with medical conditions. [16]

Practical recommendations for patients with chronic diseases who observe religious fasting clearly emphasize the need for individual risk assessment, careful selection of a treatment regimen, and, if necessary, breaking the fast. For diabetes, chronic kidney disease, and cardiovascular disease, it is emphasized that even a daytime fast followed by fluid intake may be unsafe for some patients, and dehydration increases the risk of complications. This once again demonstrates that the idea of multi-day dry therapeutic fasting, especially outside of a hospital setting, is in direct conflict with modern recommendations. [17]

Table 4. Studies on daytime dry fasting and their limitations

Type of study	Participants	Mode	Key results	Restrictions
Observational studies of Ramadan	Healthy adults, sometimes patients with certain diseases	Refusal of food and water during the day, intake of food and liquid in the evening	A slight decrease in body weight, moderate changes in lipid and carbohydrate metabolism, and the absence of severe complications in most healthy people	Small samples, short duration, no follow-up
Research on Fasting Among Baha'i Followers	Healthy volunteers	Daytime dry fasting for about 19 days a year	Improvement of some indicators of fat metabolism, absence of serious hydration disorders in healthy individuals	Patients with chronic diseases have not been studied; the regime is significantly milder than multi-day continuous dry fasting.
Experiments with complete water deprivation for 5 days	Healthy volunteers under observation	Complete abstinence from food and water for a limited period of time	Pronounced compensatory reactions are observed, without severe complications in carefully selected participants.	Small number of participants, strict selection, inability to transfer data to patients and home experiments

Risks, complications and contraindications of dry therapeutic fasting

The main and most obvious risk of dry fasting is dehydration, or water deficiency. In the early stages, it manifests as thirst, dry mouth, headache, weakness, decreased urine output, and dark urine. As it progresses, severe dizziness, low blood pressure, increased heart rate, seizures, and confusion occur. In extreme cases, severe dehydration can lead to loss of consciousness, coma, and death. [18]

The kidneys are particularly vulnerable to the combination of starvation and dehydration. A lack of fluid reduces blood flow through the kidney tissue, impairing filtration and elimination of waste products. Studies of extreme "weight cutting" in athletes, as well as data on rapid weight loss, show that severe dehydration associated with dietary restrictions can lead to acute kidney injury even in initially healthy individuals. The risk is even higher in patients with chronic kidney disease or diabetes, and some guidelines explicitly warn of the potential deterioration of kidney function with prolonged fasting. [19]

The cardiovascular system also suffers from dehydration. Thickening of the blood and decreased plasma volume increase the risk of thrombosis, including deep vein thrombosis and thromboembolic complications. Cases of thrombosis associated with prolonged fasting and dehydration have been described in the literature. In patients with coronary artery disease, heart failure, or cardiac arrhythmia, dehydration can trigger attacks of angina, arrhythmia, and deterioration of general condition. [20]

The nervous system and mental state are also sensitive to sudden changes in water and electrolyte balance. Dehydration and electrolyte imbalances can lead to seizures, acute disturbances of consciousness, and severe headaches. Cases of acute symptomatic hyponatremia following fasting followed by uncontrolled fluid intake have been described. In palliative care and ethics literature, voluntary abstinence from food and drink is considered a way to hasten death; it is noted that under conditions of complete fluid abstinence, most people die within approximately two weeks, highlighting the potentially fatal nature of such practices. [21]

Dry fasting is especially dangerous for people with chronic illnesses. In diabetes, lack of food and fluids can trigger dangerous fluctuations in glucose levels, ketoacidosis, and deterioration of kidney function. Such experiments are strictly contraindicated in patients with chronic kidney disease, heart failure, hypertension, heart rhythm disturbances, pregnancy, the elderly, and in children and adolescents. Current guidelines for the care of patients observing religious fasting emphasize that even moderate daytime fasting followed by water intake should be discussed with a doctor, and if risk factors are present, it is recommended to avoid it. The risks are disproportionately higher for multi-day dry therapeutic fasting. [22]

Finally, it's important to be clear: prolonged, deliberate abstinence from food and water is considered in palliative medicine as a way to hasten death in terminally ill patients, and in psychiatry and psychosomatics as a form of potentially self-destructive behavior. Initiating such processes in a relatively healthy person for the sake of "purging" or weight loss means knowingly exposing oneself to the risk of severe damage to health, comparable to dangerous forms of eating disorders. [23]

Table 5. Main risks of dry therapeutic fasting

Body system	Possible complications	Possible symptoms	Danger level
Kidneys and urinary system	Acute kidney injury, decreased filtration, risk of renal failure	Decreased urine output, swelling, nausea, weakness	High
Heart and blood vessels	Hypotension, arrhythmia, thrombosis, exacerbation of coronary heart disease	Dizziness, fainting, heart palpitations, chest pain, swelling of the legs	High
Nervous system	Convulsions, impaired consciousness, stroke, severe headaches	Confusion, severe headache, seizures, speech impairment	Very tall
Metabolism	Severe ketoacidosis, severe weakness, sudden weight loss	Severe weakness, acetone smell from the mouth, nausea, vomiting	High
Mental health	Increased anxiety and depression, development of destructive eating habits	Anxiety, obsessive thoughts about food and “purging,” sudden mood swings	Medium-high

Safe alternatives and practical conclusions

From the perspective of modern evidence-based medicine, multi-day dry therapeutic fasting according to Filonov cannot be recommended for weight loss, the treatment of chronic diseases, or for "cleansing" the body. Major professional societies and guidelines for preoperative patient care, obesity, diabetes, and cardiovascular disease treatments advocate preventing dehydration and avoiding prolonged periods of strict fasting, especially without medical supervision. [24]

For weight loss and improved metabolism, moderate calorie reduction and lifestyle changes have been much better studied and recommended. Obesity treatment guidelines recommend creating an energy deficit of approximately 500-750 kilocalories per day, which, on average, results in a weight loss of approximately 0.5-0.75 kilograms per week. A well-researched and safe dietary pattern with proven benefits for the heart and blood vessels is the Mediterranean diet, which emphasizes vegetables, fruits, whole grains, nuts, legumes, fish, and vegetable oils. [25]

Intermittent fasting with water retention is another option that generally shows comparable effectiveness to traditional calorie restriction for weight loss and metabolic improvement in some individuals. Importantly, these regimens do not restrict water, and the fasting periods are shorter and do not lead to significant dehydration. However, research emphasizes the need for an individualized approach and medical supervision, especially in the presence of chronic diseases, rather than blindly following strict proprietary protocols. [26]

Physical activity is an essential part of any health improvement and weight loss program. The World Health Organization recommends that adults get at least 150-300 minutes of moderate or 75-150 minutes of vigorous aerobic activity per week, supplemented by strength training for large muscle groups at least twice a week. This level of activity has been proven to reduce the risk of cardiovascular disease, type 2 diabetes, and certain cancers, and helps maintain a healthy body weight. [27]

Practical conclusion: if the goal is to lose weight, improve well-being, or reduce the severity of symptoms of a chronic disease, it is safer and more reasonable to rely on methods with a convincing evidence base - dietary changes, increased physical activity, psychotherapeutic support when necessary, and, if indicated, drug therapy under the supervision of a physician. Multi-day dry fasting, especially according to strict proprietary schemes, cannot be viewed as a harmless "health experiment": in terms of its risks, it is closer to dangerous forms of eating disorders and practices used in palliative medicine to accelerate death. Any ideas about long-term abstinence from water and food should be discussed with a doctor, and even better - replaced with safe and evidence-based approaches to self-care. [28]

Table 6. Dry therapeutic fasting and evidence-based alternatives

Approach	The essence	Level of evidence	Main advantages	Main risks
Dry therapeutic fasting according to Filonov	A multi-day complete abstinence from food and water according to the author's scheme	No large controlled clinical trials, not in guidelines	Rapid weight loss due to water and tissue (mostly short-term)	High risk of dehydration, damage to the kidneys, heart, nervous system, thrombosis, severe metabolic disorders
Moderate reduction in caloric intake	Energy deficit of about 500-750 kilocalories per day, for a long time	Supported by numerous studies and clinical guidelines	Moderate but sustained weight loss, improvement in risk factors, good tolerability	Requires discipline and planning, and may result in slow progress.
Mediterranean diet	A diet rich in plant foods, fish, and vegetable oils	Large randomized trials have shown a reduction in cardiovascular risk	Improved lipid profile, blood pressure, reduced risk of heart attack and stroke, beneficial for most people	Adaptation of habits is necessary, financial and cultural limitations are possible
Intermittent fasting with access to water	Reducing the food intake window while maintaining normal hydration	A number of randomized trials show comparable effectiveness to a traditional diet	Convenient for some people, helps control calories, has potential metabolic benefits	Not suitable for certain illnesses, medical supervision required, possible hunger attacks and breakdowns
Comprehensive lifestyle modification	A combination of diet, physical activity, and behavioral support	The strongest evidence base for weight loss and reduced risk of chronic diseases	Long-lasting results, improved quality of life, reduced risk of many diseases	It requires time, systematic work and specialist support.