Can fasting for 2 days restart the human immune system? Scientists have discovered

“Fasting for 2 days resets the entire immune system!”

“Hungry is a natural way to stay healthy!”

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Similar claims have made countless “wellness lovers” flock to it. Does fasting really have so many health benefits?

The claim that fasting restarts the immune system stems from a study by the University of Southern California in 2014. The paper was published in the top journal “Cell Stem Cell” [1] .

This study sought to examine the effects of prolonged fasting on immunosuppression induced by chemotherapy and aging.

The study used mice.

Scientists divided the mice into two groups, A and B. Group A ate freely, and group B received multiple “fasting-refeeding” dietary interventions, with a fasting duration of 24~ 72 hours vary.

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The researchers then administered chemotherapy drugs to the mice at fixed time points to observe their blood immune-related indicators, including white blood cell counts, lymphocyte counts, and so on.

The results showed that the chemotherapeutic drugs impaired hematopoiesis in the mice. However, the immune-related indicators of the freely fed mice in group A were always in a state of“collapsed”;after a period of fasting, the immune-related indicators of the mice in group B showed significant immunity-related indicators. improvement.

Through follow-up cell experiments, the researchers found that such results may be attributed to the “fast-refeed” dietary cycle pattern, which regulates the mice Some special hormones in the body, such as insulin-like growth factor 1 (IGF-1), inhibit the damage of chemotherapy drugs on the hematopoietic system and promote the reconstruction of hematopoietic function.

Researchers achieved similar results in aging mice.

Study concludes that prolonged fasting has great therapeutic potential to improve or reverse immune aging caused by aging , and chemotherapy-induced immunosuppression.

The immune system is like a scavenger and bodyguard, sweeping away various internal and external pathogenic factors for us, and helping humans resist diseases.

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But with natural aging, or some special treatment such as chemotherapy, the immune system may have to “compromise” – their power is suppressed or weakened, and they are unable to fight anymore Disease-causing factors, which is why some special groups are more likely to get sick, and it is difficult to recover after illness.

This study does provide a potentially effective dietary treatment option, but no dietary intervention or treatment can be based on a single document /strong>As a basis. There are several reasons:

1. Research is based on animal experiments and cell experiments, and there are essential differences between animals and humans.

Cells are grown in a in vitro environment, which is very different from the internal environment of the human body.

The results of animal and cell experiments can only be said that such ideas have certain value, and further verification in designated populations is needed to confirm true effectiveness and safety strong>.

It is by no means like self-media, which arbitrarily applies the results directly to people.

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2. The so-called “long-term fasting” term, in this study, the mice were fasted for 24 to 72 hours, and then re-fed, according to a certain Cycle to cycle, intervene.

The average person reacts completely differently when they see words like “long fast”, which can be misleading. Some people may starve themselves for a long time and be in a state of severely insufficient calorie and nutrient intake. Over time, it will evolve into malnutrition, causing physical and mental suffering. Doing so is equivalent to chronic self-harm!

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3. For the elderly and patients receiving chemotherapy, nutritional interventions should refer to the corresponding discipline guidelines.

These guidelines compile many of the latest, high-evidence research findings for guidance. A single study alone is not enough to provide strong evidence.

4. Blind fasting may have many adverse reactions, even if you want to try it, it should be done under the guidance of a doctor. You must not listen to the “popular science” of some self-media, and test yourself at home.

Some we-media favorites play word games. “Immune restart” gives the illusion of “resurrection”. In fact, it may be only the improvement of some indices, and whether it has clinical significance needs further verification.

Oncology patients undergoing chemotherapy are at high risk of developing malnutrition [2]. This is because chemotherapy can directly affect metabolism, or cause problems such as nausea, vomiting, loss of appetite, dysphagia, digestive and absorption dysfunction, and interfere with the intake and utilization of nutrients[2].

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Malnutrition itself can damage immune function, which is equivalent to adding fuel to the fire on the basis of the toxic and side effects of chemotherapy.

Malnutrition also reduces plasma albumin levels and reduces the body’s ability to tolerate chemotherapy [2].

Thus, chemotherapy patients who blindly believe in the “superpowers” of prolonged fasting may lead to further deterioration of nutritional status and an even more dangerous vicious cycle.

As for older adults, they experience a decline in all aspects of the body, including chewing and digestion, enzyme activity, and hormone levels [3]. Compared with ordinary adults, they are at greater risk of malnutrition, such as muscle loss and osteoporosis.

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Inadequate daily dietary intake only increases the risk of nutrient deficiencies, infectious and chronic non-communicable diseases[3].

Therefore, the weight standard of the elderly can be appropriately increased and maintained at the body mass index (BMI=weight (K)/height squared (O)) 20~26.9 strong> is ideal [3].

For the average person, intermittent fasting to control energy intake may be beneficial.

Intermittent fasting is the practice of strict eating on a regular basis throughout the day or week.

Keeping to eat less or no food for a period of time can effectively control the level of calorie intake not exceeding the standard, improve metabolic status, enhance resistance, maintain health and resist diseases [4].

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There are 3 modes that are used the most:

1. Alternate-day fasting: Fast once every other day. But on the day of fasting, it is not to eat nothing, but to ensure that the total energy intake on the day does not exceed 500 to 600 kcal, which is equivalent to eating only one meal. Eat normally at other times.

2. 5+2 fasting method: Within 7 days, choose 2 non-consecutive days, and control the energy intake to 1/4 of the daily (about 1/4) 500 kcal for women and 600 kcal for men), and eat normally for the remaining 5 days.

3. Time-restricted eating method: It is required to select 6 to 8 consecutive hours within 1 day as the time period for allowing eating, and the remaining 16 to 18 hours hours without eating.

But there is a gap between theory and reality.

Intermittent fasting is not in line with the mainstream food culture of “three meals a day”, and it is difficult to stick to it when it comes to social events or gatherings with friends.

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Emotional problems (such as irritability), insomnia, and inefficiency at work and study may occur during fasting.

Ordinary people cannot fast casually, but require regular assessment and monitoring by a nutritionist to avoid nutritional imbalances.

All of these make fasting very high, and even a burden on life and spirit.

Actually, we can achieve the same as “intermittent fasting” by improving dietary patterns and food choices while maintaining normal eating habits Purpose.

You can refer to the recommendations of the 2016 Dietary Guidelines for Chinese Residents:

Maintain a balanced meal pattern;

Let rough, fresh, nutrient-rich foods such as fresh vegetables and fruits, whole grains, fish, eggs, and milk always occupy the “C position” of your recipe;

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Strictly limit foods high in sugar, salt, fat, calories, and low in dietary fiber and micronutrients (such as sugar-sweetened beverages such as cola, sweets, puffed foods, etc.).


1. Nutrition and dietary interventions are not as simple as “no meals,” but are based on scientific evidence, using methods proven to be safe and effective in improving your condition.

2. The extreme fasting method that is free from control and scientific concepts, such as eating only apples or cucumbers for several days, or even drinking only water, is a “wacky way” that attracts people.

3. Be sure to look at the crazy articles on the Internet rationally. If you want to control your diet and energy intake, you must do it under the guidance of doctors, nutritionists, etc.

Reviewer: Shi Zhengli| Nutritionist, Department of Nutrition, Beijing Friendship Hospital


[1]Cheng C, Adams G, Perin L et al. Prolonged Fasting Reduces IGF-1/PKA to Promote Hematopoietic-Stem-Cell-Based Regeneration and Reverse Immunosuppression. Cell Stem Cell. 2014;14(6):810-823. doi:10.1016/j.stem.2014.04.014

[2] China Anti-Cancer Association, Professional Committee of Cancer Nutrition and Supportive Care of China Anti-Cancer Association, etc. Guidelines for Nutritional Treatment of Chemotherapy Patients. Electronic Journal of Tumor Metabolism and Nutrition. 2016;3(3) :158-161.

[3]Chinese Nutrition Society. Dietary Guidelines for Chinese Residents 2016.

[4]de Cabo R, Mattson M. Effects of Intermittent Fasting on Health, Aging, and Disease. New England Journal of Medicine. 2019;381(26):2541-2551. doi :10.1056/nejmra1905136

*The content of this article is for the popularization of health knowledge and cannot be used as a specific diagnosis and treatment suggestion, nor can it replace the face-to-face consultation of a licensed physician, and is for reference only.

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