Advantages and disadvantages of intermittent fasting: Are long meal breaks helpful?

  • William Park
  • BBC Future

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It has long been considered that for health and silhouette it is useful to eat often and in small portions. Lately, however, among celebrities and prominent representatives of the business world, the fashion of the so-called intermittent fasting prevails. Help your body without giving up the habit of tasty and satisfying food, but only by changing the meal plan? The temptation is great. Let’s take a look at the pros and cons of this method.

There is some evidence that cleverly practiced fasting can help you lose weight, improve your health, and even prolong your life, but nutritionists recommend caution.

The main point of the intermittent fast is not to eat in the evenings, increasing the interval between the last and the first meal. His supporters usually give the number at 16 o’clock.

Some emphasize the amount of food and promote the “5: 2 diet” (normal diet five days a week and reduction of calories by four in the remaining two days).

“Time limits are used as a weight loss tool, but I can not say that this is my favorite approach,” said Rachel Clarkson, founder of the London-based DNA consulting firm Dietitian. “You reduce calories, but you do not change your approach to what you put in your body.”

According to her, without understanding what a healthy diet is, people, after fasting, quickly gain their previous weight. “If you feel hungry and perceive it as a limitation, then the next day you will probably be very full,” says the expert.

Intermittent fasting may not be the best way to stay lean, but there are other arguments in favor of it. It is associated with autophagy, a natural regenerative process that occurs at the cellular level and is of great interest to scientists because of its supposed benefits for humans.

Autophagy? This is useful!

Autophagy (“autophagy”) is a natural mechanism of disassembly and recycling into living cells of their redundant and non-functional parts, including nuclei that store DNA, mitochondria that chemically convert nutrients into energy, and lysosomes. waste.

Thus, the body gets rid of toxins and receives useful substances. Some of them are converted into protective proteins that increase cell resistance.

Scientists are trying to find out if autophagy helps to increase the lifespan of the whole organism. Suppressed autophagy has been shown to lead to premature aging, but so far such data have only been obtained in experiments on mice and nematodes (one millimeter long worms).

Long-term observations are needed to test this hypothesis in humans and to confirm the link between autophagy and intermittent fasting.

Can controlled abstinence activate it?

Unlike low-calorie diets (which are also linked to longevity), intermittent fasting aims to increase the gap between dinner and breakfast.

Theoretically, his fans consume the same number of calories, although Rachel Clarkson notes that, according to her observations, in practice it is slightly reduced. The main thing is what happens after eating.

“After your last meal at 7:00 pm, you will be full until about 22:00 as your body continues to metabolize the food you have received,” he says. hours “.

The feeling of fullness means that glucose has entered the bloodstream and is being converted into energy. When it dries – this happens on average three hours after eating – the body falls into a catabolic state, that is, it begins to process the polysaccharides that accumulate in the liver and muscles into glucose.

When this energy source is depleted, the body switches from glucose to ketones produced by the liver from fatty acids. This condition is called ketosis and at this stage autophagy is activated.

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Even the lightest snack before bed prolongs satiety, so you probably will not reach the desired ketosis state.

“It is impossible to pinpoint the timing of the transition from glucose to ketones,” says Clarkson. “It depends on many factors: genetics, health status, lifestyle, how much you ate before and how much energy you spent.”

In a person who consumes a lot of carbohydrates, ketosis almost never occurs, since his body contains a store of polysaccharides. For those who eat little sweets and exercise regularly, this can happen quite quickly.

Similarly, the low-carb keto diet, which is followed to lower blood sugar levels, works.

“I would not go on an intermittent fast to burn fat, and those who do should consider the health effects,” says Clarkson.

How to fast properly

“To be hungry, you must first learn to control the feeling of hunger,” he explains.

The feeling of hunger occurs when the hormone ghrelin produced in the stomach begins to stimulate the hypothalamus to produce two other hormones, the neuropeptide Y and the agate-like peptide (AgRP).

These substances create a feeling of hunger, while others, the so-called “satiety hormones”, suppress it. The latter include, for example, leptin, which is produced by fat cells and inhibits ghrelin synthesis. It seems to signal to the body: “there is still enough fat”.

Ghrelin is sometimes referred to as the rapid response to hunger because it is produced immediately when the stomach is empty and the pressure on its walls is relieved. To some extent, this can be combated with drinking water. Leptin, on the other hand, works for a long time.

“The production of hunger hormones is regulated by many factors, including individual genetics,” says Clarkson. “But the main role is played by the nerve endings in the stomach and the digestive system. “If the stomach is not tense, the body thinks it is hungry.”

He added that plenty of hydration can deal with this feeling at first – until the body gets used to a smaller amount of food: “The first two weeks will be difficult and then you will adjust.”

For most people, ketosis starts between 12-24 hours after a meal. So if you ate dinner between 6:00 p.m. and 8:30 p.m., saturation will end at 9:00 p.m.-23: 30 p.m. and ketosis and autophagy will begin at 06: 00-8: 30 p.m. next morning.

“But most people are looking for something to eat at the first sign of hunger,” Clarkson said. hour, or even until three in the morning. “

This means that ketosis will not happen at all – a person will have breakfast first.

“If you consciously decide to eat dinner an hour earlier and do not touch the food after that, you have the opportunity to go into a state of ketosis until the morning – unlike those who, after a high-carbohydrate dinner, also have a snack. “And then I get up at six in the morning,” says Clarkson.

The expert advises you to start getting used to dinners early on Sunday night, on Monday to have breakfast one hour later and thus gradually add one or two days a week.

With a thoughtful approach, intermittent fasting can sometimes help the body heal itself. Autophagy weakens with age and artificial stimulation is not harmful.

But you should not place too much hope in it when it comes to fighting overweight. We must remember that fasting is not a substitute for a balanced diet.

The contents of this article are for general information only and are not a substitute for professional medical advice and assistance. The BBC recommends to anyone interestedthe issue of intermittent fastingTo avoid possible side effects, consult a specialist first.

The BBC is not responsible for any diagnosis or action taken or as a result of reading this article, nor for the content of other sites which contains links to and is not involved in the marketing of the products and services offered on it. If you are worried about your health or your healththeir loved onesAlways consult your doctor.

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