Scientific facts about therapeutic fasting: how the body adapts to going without food, how fasting renews the immune system, how it may help in cancer treatment, and why it could become a way of life.
The practice of therapeutic fasting has been known since ancient times. Yogis actively use this tool to keep their bodies in good condition. Controlled abstention from food is believed to help people lose weight, get rid of many illnesses and even prolong life. Modern science has only recently begun to study the effects of fasting on the body, but it has already made some progress on the question.
What is therapeutic fasting?
Therapeutic fasting means voluntarily refraining from food, or even from water (so-called dry fasting), for a certain period of time — from 12 hours or more. There is a huge number of different fasting methods: one-day fasting, prolonged fasting, intermittent fasting, fasting on juices and herbal infusions, dry fasting and so on.
How the body adapts
Special metabolic adaptations help our body get through a fast. Our main source of energy is glucose. We get it from food and use it as needed. On average, one meal is enough to supply the body with glucose for four hours. If no new portion of glucose arrives after that time, the body starts using its reserves, which are stored in the liver as glycogen. Depending on physical activity, after 12–24 hours the blood glucose level drops by about 20% and the glycogen reserves are exhausted. At the same time, however, gluconeogenesis begins in the liver cells — the synthesis of glucose from muscle proteins, ketone bodies (BHB) and glycerol. The newly synthesized glucose and the ketone bodies go to feed the brain, while the other tissues feed on fatty acids. In this way a person can go without food for 30 days or more, depending on their build, the amount of fat and how active gluconeogenesis is. King penguins, for example, can last up to five months without food.
It turns out that when we stop eating, the brain is the last to go hungry, and the body restructures its metabolism so as to supply our central computer with glucose. From an evolutionary point of view, this means that keeping the brain working normally is the most important task during fasting.
During fasting, the amount of some substances in the blood (ketones and the hormone ghrelin) increases, while the amount of others (insulin and leptin) decreases. These changes affect brain activity, stimulating the formation of new neurons and the activity of neural networks, and optimizing the metabolism of the brain and the peripheral organs.
As a result of these processes we see:
- increased activity of the parasympathetic nervous system;
- improved bowel function;
- a slower heart rate and lower blood pressure;
- increased insulin sensitivity of muscle cells, and therefore better absorption of protein and carbohydrates;
- a lower level of oxidative stress, which is the cause of many serious diseases, including chronic fatigue;
- the body clearing itself of damaged cells;
- enhanced cellular bioenergetics — the process by which cells produce energy;
- less inflammation in the body.
Studies that scientists carried out on rats have also shown that alternating fed days and fasting days in mammals sharpens sensory and motor activity and improves learning ability and memory.
Renewal of the immune system
In 2014, scientists from the University of Southern California (USA) published a paper describing another positive effect of fasting: the renewal of the immune system. In an experiment on mice that lasted six months, the rodents were periodically given periods of two to four days without food. This caused the number of white blood cells in their blood to fall. But when they were fed again, the level of immune cells rose.
The scientists concluded that hunger made the mice not only use up their nutrient reserves but also "eat" their old immune cells. These worn-out and damaged white blood cells could no longer work well, so when nutrients were scarce they were simply digested. And the disappearance of the old, poorly working immune cells set off a process that activated blood stem cells. A regenerative program was switched on in them, and they began to divide and generate new white blood cells. So a series of short fasts gave a double result: it helped remove old cellular debris and replace it with new cells.
Fasting and cancer
The idea that prolonged fasting helps cure cancer appeared a long time ago. But until recently there was no scientifically grounded evidence for it. Research carried out over the last 20 years by scientists in the USA and Europe, however, has shown that combining fasting with chemotherapy gives positive results in treating certain types of cancer.
Experiments that scientists have carried out on mice give grounds for hope that periodic fasting may be as effective in cancer treatment as chemotherapy. Such fasting also helps protect the body from the harmful effects of various chemotherapy drugs. This is explained by the fact that periodically recurring extreme conditions — namely fasting and the reduced calorie intake that goes with it — increase the stress resistance of the body's healthy cells and make it harder for cancer cells to adapt to such extreme conditions. Faced with the double stress caused by drugs and hunger, cancer cells cannot adapt and die, while healthy cells successfully protect themselves. As a result, among the test mice most prone to developing metastases, the combination of fasting and chemotherapy allowed 20–60% of the animals to survive. Using fasting or chemotherapy alone did not give such results.
Fasting as a way of life
Scientists around the world who study the effects of fasting on the body agree that periodically going without food should become a way of life for anyone who wants to be healthy and to lower the risk of developing chronic diseases. And the researchers have every reason for this view. Experiments have already shown that fasting has a positive effect on such health markers as insulin sensitivity, blood pressure, inflammation, the amount of body fat, IGF-1 (insulin-like growth factor 1) and the lipids that cause atherosclerosis. It also helps with a wide variety of problems: cardiovascular disease, type 2 diabetes, Alzheimer's disease and so on.
Still, don't rush to drop everything and go on a hunger strike. It is very important to remember that this practice is far from suitable for everyone, or at every time. It has a number of contraindications and is not recommended for children or for very elderly and exhausted people. So before trying fasting, it is best to consult a doctor or a nutritionist first.
It is also very important to pay attention to your diet between fasts. For example, researchers note that an unbalanced diet — when a person piles into very high-calorie food between fasting days — can upset the circadian rhythm (the body's internal biological rhythm) and affect the functioning of the endocrine and digestive systems. Here it is best to consider a vegetarian diet, which, combined with the practice of fasting, gives very good results.
Sources:
- Kirill Stasevich, "Hunger renews the immune system" (Nauka i Zhizn, no. 5, 2014)
- N. L. Reznik, "Should the belly be kept hungry?" (Khimiya i Zhizn, no. 7, 2017)
- Valter Longo, Mark Mattson. "Fasting: Molecular Mechanisms and Clinical Applications" (Cell Metabolism, 2014).
