The cheapest diet
Is there any benefit from fasting?
Marina Berkovskaya, Post-science
If you eat less, you can live longer – so say the supporters of starvation. Overweight is associated with the development of diabetes, cardiovascular diseases and cancer. Does this mean that periodic refusal of food can be good for health? Together with nutritionist and endocrinologist Marina Berkovskaya, we figured out how fasting affects the body, in which cases it can benefit and who should not starve in any case.
Fasting against obesity
According to WHO, about 1.7 billion people worldwide are now overweight, with 500 million of them obese. At least 2.6 million people die from obesity every year, and overweight is associated with the development of diseases such as cancer, cardiovascular diseases and diabetes. All these figures bring us to an unpleasant fact: modern man chronically overeats.
This is due to several factors. Firstly, modern people spend many times less energy than our ancestors did: a different lifestyle, work, as a rule, is mental, less motor activity. Secondly, food has become much more affordable, and its calorie content has increased. Thirdly, food in the modern world performs not only its direct, nutritious function, but also social: many holidays and just meetings with colleagues and friends are most often held at the table. We are increasingly faced with disharmonious relationships between a person and food, which leads to the formation of harmful eating habits and eating disorders.
Realizing this problem, people begin to cope with it by the most well-known methods: diets, sports and therapeutic fasting. We will focus on the last item on this list, the most ambiguous. In Russia, fasting has been popular since the days of Soviet medicine. In 2005, the Ministry of Health even issued a manual for doctors on how to properly apply fasting and dietary therapy (in fact, fasting) in restorative medicine. However, some scientists question the effectiveness of prolonged fasting.
Thus, the WHO says that due to prolonged fasting, there may be a lack of essential vitamins and minerals in the diet, and this negatively affects the immune system and healthy human development. Hunger and inadequate nutrition contribute to a slowdown in physical development, including the brain, at a young age. In the end, you can just die of hunger.
An effective method of combating obesity is a moderate reduction in the caloric content of the diet. It has been proven that this approach to gradual weight loss works and, in addition, contributes to the prolongation of life. Hypocaloric nutrition is associated with the elongation of telomeres (DNA regions responsible for cell lifespan), stimulation of sirtuins (genes that encode proteins that regulate metabolism), a decrease in the activity of the mTOR gene (due to which excessive inflammation is suppressed and aging of the body slows down), due to which, according to scientific data, life expectancy can increase. But we are talking about reducing the caloric content, when a person receives the energy he needs, just in a slightly smaller volume. When fasting, even "therapeutic", the body behaves differently.
What happens to the body during fasting
After 10-14 hours, the body begins to consume glycogen reserves in the liver (glucose depot as the main source of energy) and produce ketone bodies. These are fatty acid oxidation products: acetone, acetoacetate and beta-hydroxybutyrate. The body will utilize them instead of glucose and get energy through the oxidation of ketones.
This condition is called physiological ketosis. It is on this principle that the famous ketogenic diet (keto diet) is built. With ketosis, ketones will be contained in the blood and urine of a person, but not in such an amount as to reduce the acidity of the blood. That is, ketosis will not have a toxic effect on the human body, but it will ensure its energy consumption during fasting.
At this point, the amount of glucose will decrease, but its concentration will still remain within the permissible norm due to the process of gluconeogenesis. From substrates such as lactate coming from muscle tissue, red blood cells, glucogenic amino acids from the gastrointestinal tract, glycerin from adipose tissues, the body will create the necessary amount of glucose. When gluconeogenesis also exhausts itself, the body will face a shortage of nutrients, which will lead to serious health consequences.
What happens after returning to a normal diet
After a short-term fasting, up to 5-7 days, nothing critical is likely to happen, a person will simply switch from ketogenic to carbohydrate metabolism. The worst thing that can happen is a rapid set of lost mass. Moreover, the body will replace the lost muscle mass with fat.
After prolonged fasting, the resumption of food intake may be accompanied by various variants of refeeding syndrome (refeeding syndrome – syndrome of renewed nutrition). The first reports of refiding syndrome appeared after the Second World War, it was observed in women who survived in concentration camps. The syndrome develops in people who begin to receive food after a long fast: people with anorexia or patients with malabsorption, malabsorption of macronutrients, vitamins and trace elements in the small intestine. After the resumption of nutrition, patients with refeeding syndrome develop serious violations of the water-electrolyte balance, characterized by a deficiency of phosphorus, magnesium and potassium. This is a serious, potentially fatal condition. And from the point of view of physiology, the first thing that nutritionists fear after long periods of fasting is various variants of refeeding syndrome.
There are also serious psychological consequences of fasting, which are much more common than refeeding syndrome. We are talking about a compensatory hyperphagic reaction to starvation, when a person begins to have problems with the perception of food after periods of refusal from food and there is a craving for overeating. In the USA in the twentieth century, a study was conducted on 40 young people who refused from the army. For six months, their daily caloric intake was limited to 800 kcal, that is, instead of the prescribed 2.5–2.6 thousand kcal, they ate only 1.8 thousand. Six months later, these people began to focus very much on food. Some took about a year to normalize their eating behavior. Some said that even after 9 months they could not treat food as simply and calmly as before the study.
Why are people starving
It is generally believed that fasting is a universal method of combating many diseases. So, in the USSR and In Russia of the twentieth century, there was a fairly popular method of fasting by Paul Bragg, who recommended "detoxes" for 24 hours "from breakfast to breakfast". Allegedly due to this, the body begins to digest toxins and foreign cells, the mechanism of self-healing, laid down by evolution, is activated. However, doctors criticized his book "The Miracle of Fasting" and the effects that Paul Bragg promised his readers. By the way, Bragg's translator Steve Shankman wrote that Paul died at the age of 95 while surfing. In fact, the writer died of a heart attack in the emergency department of a hospital at the age of 81.
The term "unloading and dietary therapy", which we mentioned above, is officially recognized by the Ministry of Health. But there is no serious evidence base of studies confirming its benefits in the long term. With the exception of acute conditions requiring temporary starvation, for example acute cholecystitis, chronic disease can not be cured by refusing food. For example, if a person with hypertension is starving, his blood pressure may decrease slightly during fasting, including due to a decrease in the concentration of sodium in the blood, but arterial hypertension will also return to the usual diet. In this case, it is more logical to choose a diet limited in calories and certain foods: simple carbohydrates, salt, excess saturated fats.
Another argument of the ideologists of fasting concerns the renewal of hematopoietic stem cells against the background of fasting. The studies were carried out on people suffering from oncological diseases who were specifically not given food before chemotherapy courses. This made it possible to reduce the severity of side effects associated with the toxic effects of drugs on hematopoiesis (hematopoiesis), however, science has no evidence that fasting promotes rejuvenation of stem cells of a healthy organism.
Nutritionist, endocrinologist Marina Berkovskaya:
Can we talk about at least some benefit from fasting for a conditionally healthy person? I am deeply convinced that it does not exist. In my practice, I see many patients who starve and then gain weight again. A person likes to eat by nature, so after a week of fasting, he begins to eat more and often begins to compulsively overeat. That is, it makes itself worse than before starvation.
What about interval fasting?
Interval fasting implies various nutrition schemes in which meal intervals are prescribed. For example, the most popular scheme is 16/8: you need to spend 16 hours without food, you can eat in the remaining 8. There are other options: 5/2 – when a person eats as usual for five days, and in the remaining 2 days introduces a strict calorie restriction: no more than 600 kcal per day for men and 500 kcal per day for women. There are many schemes, and in principle they differ only in the regime of alternating periods of hunger: 36/12, 18/6, 20/4, 14/10, 12/12.
Proponents of interval fasting say that our bodies are evolutionarily well adapted to periods of fasting up to 20 hours. Periods of hunger are accompanied by changes in the metabolism of tissues that begin to consume ketones. Ketones are secreted by adipose tissue and replace glucose, the concentration of which drops. Episodes of ketosis during interval fasting alternate with periods when cells feed on glucose, which comes in sufficient quantities after eating. It is believed that during ketosis, the body resists stress better, and the period of increasing glucose and insulin concentrations is associated with growth and increased plasticity of tissues.
In 2019, a group of German scientists published a study according to which interval fasting did not demonstrate negative health effects even for six months. Therefore, for overweight people, doctors can prescribe the practice of interval nutrition as a treatment. At the same time, it is very important that patients do not have contraindications – for example, cholelithiasis and a number of other diseases of the gastrointestinal tract (predisposed individuals with fasting increase the risk of developing gallbladder pathology).
Despite the positive effects of interval fasting in relation to overweight, the question remains how realistic is the introduction of interval fasting into the treatment strategy of patients, for example, with obesity. This approach can indeed show high efficiency, but there are also two difficulties. The first is social: because of the new diet, a person will have to rebuild his whole life: perhaps, skip some events, see less of his friends. The second is psychological. People are fine with fasting when it happens during the study period, because they know that it will end soon. But if you carry this experience for a lifetime, dietary depression can develop, as well as eating disorders. Like any diet or restriction, interval fasting is fraught with disruption, rejection of the diet and a new intensive weight gain.
A person who has decided to switch to interval fasting should pay attention to two main points. The first is how he will integrate a new food system into his life. Interval fasting makes sense to implement indefinitely, it does not give a quick effect, so it should be comfortable both psychologically and physically, it should correspond to the rhythm of life and physiological needs. Interval fasting has advantages over a chaotic diet, when a person takes food without observing any regime and even sometimes without feeling hungry, which disrupts circadian rhythms, does not allow the digestive system to adjust the mode of production of digestive juices, and also often leads to overeating.
The second nuance is that it is better to have an early interval meal. That is, it's worth skipping dinner, not lunch or breakfast. The human body is adapted to ensure that the digestion of food coincides with active wakefulness. At night, the digestive system should rest: the motility of the gastrointestinal tract slows down, the secretion of digestive juices decreases, fat-burning hormones such as melatonin, growth hormone are produced. Therefore, when eating at night, it is easy to deprive yourself of the peak of "fat burning", which contradicts the very idea of fasting.
The attitude of the medical community to interval fasting is gradually changing. So, in 2019, a large article about the benefits of interval fasting was published in the most authoritative medical journal The New England Journal of Medicine. The authors concluded about the benefits of this style of nutrition in patients with hypertension, diabetes mellitus, and lipid metabolism disorders. Interval fasting can increase the ability to resist mental stress, reduce systemic inflammation, improve memory and cognitive abilities. Together with the restriction of calories, it can presumably be an effective method of prolonging life.
As working schemes of fasting, the authors recommend two. The first involves limiting the window during which food is taken. It gradually narrows from a ten-hour interval five days a week to a six-hour window all seven days a week (respectively, fasting occurs for 18 hours a day). The second scheme is 5/2, which involves limiting food intake to less than 500 calories for two days during the week.
Who exactly should not starve
In the text, we have already noted several contraindications for fasting, now we will put them together. First of all, people with a body weight deficit should not starve if this deficit is 15% or more of the normal weight. Also, this method is contraindicated if you have an eating disorder.
Of course, fasting should be avoided during pregnancy and lactation. WHO warns that insufficient nutrition of mothers leads to unfavorable fetal development and the risk of pregnancy complications. In addition, according to the organization, malnutrition of mothers and children accounts for more than 10% of the global burden of diseases.
Special care should be taken in patients with type II diabetes mellitus, since many of them take medications that reduce blood glucose levels. Taking, for example, insulin and sulfonylurea derivatives is accompanied by an increased risk of hypoglycemia (reduced concentration of glucose in the blood), and in the case of fasting, this risk increases if you do not change the medication regimen.
As we have already said, fasting will not help to cure severe chronic diseases. Moreover, serious somatic pathologies, such as heart failure, kidney failure, cirrhosis of the liver, cardiac arrhythmias, recent heart attack and stroke in the anamnesis, gallstone disease, gastric ulcer and duodenal ulcer – all these are reasons to abandon the idea of fasting and focus on the total caloric content and balanced diet.
About the author: Marina Berkovskaya – Candidate of Medical Sciences, assistant of the Department of Endocrinology at Sechenov University.
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