Last updated date: 11-Mar-2024

Medically Reviewed By

Medically reviewed by

Dr. Hakkou Karima

Medically reviewed by

Dr. Lavrinenko Oleg

Originally Written in English

Intermediate Fasting

    Intermediate fasting or intermittent fasting is a weight loss approach that has existed in various forms for ages. Intermittent fasting (IF) is an eating design that cycles between times of fasting and eating. It doesn't indicate which food varieties you ought to eat but instead when you ought to eat them. In this regard, it's anything but an eating routine in the ordinary sense yet more precisely depicted as an eating pattern. Normal intermittent fasting strategies include daily 16-hour diets or fasting for 24 hours, two times a week. Fasting has been a practice all throughout human evolution. Subsequently, people advanced to have the option to work without nourishment for extended periods of time.Indeed, fasting every now and then is more natural than continually eating 3–4 (or more) meals each day.

    Fasting is likewise frequently accomplished for strict or profound reasons, including in Islam, Christianity, Judaism and Buddhism.


    Intermittent Fasting Methods

    There are a few distinct methods of doing intermittent fasting — all of which include parting the day or week into eating and fasting periods. During the fasting time frames, you eat either nothing or very little. These are some of the most used strategies:

    • The 16/8 method: Also called the Leangains protocol, it includes skipping breakfast and limiting your every day eating period to 8 hours, for example, 1–9 p.m. Then, at that point you fast for 16 hours in between.Numerous individuals track down the 16/8 technique to be the easier, generally reasonable and most straightforward to adhere to. It's likewise the most famous.
    • Eat-Stop-Eat: This includes fasting for 24 hours, more than once per week, for instance by not having from dinner one day until dinner the following day.
    • The 5:2 diet: With this strategy, you consume just 500–600 calories on two nonconsecutive days of the week, yet eat ordinarily the other 5 days.

    By lessening your calorie intake, these strategies should lead to weight loss as long as you don't repay by eating substantially more during the eating time frames.


    How does intermittent fasting affect your cells and hormones?

    When you fast, a few things occur in your body on many levels. For instance, your body changes hormone levels to make body fat more accessible. Your cells likewise start significant repair cycles and change the expression of genes.Here are a few changes that happen in your body when you fast:

    • Human Growth Hormone (HGH): The levels of human growth hormone go up, as much as 5 times. This has benefits for fat loss and muscle gain.
    • Insulin: Insulin sensitivity improves and levels of insulin drop significantly. Lower insulin levels make stored fat more accessible.
    • Cellular repair: When you fast, your cells start repair processes. This incorporates autophagy, where cells digest and eliminate old and broken proteins that build up inside cells
    • Gene expression: Fasting leads to changes in the function of genes related to longevity and protection against diseases.


    Intermittent fasting as a weight loss tool

    Weight reduction is the most widely recognized justification for attempting intermittent fasting.

    By causing you to eat fewer meals, intermediate fasting can prompt a programmed decrease in calorie intake. Also, intermittent fasting changes chemical levels to work with weight loss. As well as bringing down insulin levels and increasing growth hormone levels, it increases the release of the fat consuming hormone norepinephrine (also known as noradrenaline).

    Due to these changes in hormone levels, your metabolic rate might increase by 3.6 to 14%.

    By assisting you with eating less and consuming less calories, intermediate fasting causes weight loss by changing the two sides of the calorie equation. Studies show that intermittent fasting can be an incredible weight loss tool. A 2014 review study tracked down that this eating pattern can cause 3 to 8% weight loss over 3 to 24 weeks, which is a lot, compared to most weight loss plans.The same study reported that individuals additionally lost 4 to 7% of their waist circumference, showing a huge loss of unsafe fat that develops around your organs and causes disease. Another study showed that intermittent fasting causes less muscle loss than the more standard method for constant calorie limitation. In any case, remember that the primary justification for its prosperity is that intermittent fasting assists you with eating less calories overall. In the event that you eat huge amounts of food during your eating periods, you may not lose any weight whatsoever.


    Are there any health benefits of intermittent fasting?

    Intermittent fasting

    Numerous studies have been done on intermediate fasting, in animals as well as humans. These studies have shown that it can have incredible advantages for weight control and the soundness of your body and cerebrum. It might even help you live a longer life.

    Here are the primary medical advantages of intermediate fasting:

    • Weight loss: As referenced above, discontinuous fasting can assist you with getting more fit and get rid of stomach fat, without having to deliberately restrict calories
    • Insulin resistance: Intermittent fasting can diminish insulin resistance, bringing down glucose by 3–6% and fasting insulin levels by 20–31%, which can protect you against type 2 diabetes.
    • Inflammation: Some studies show decreases in markers of irritation, a key driver of numerous ongoing chronic illnesses .
    • Heart wellbeing: Intermittent fasting may decrease "awful" LDL cholesterol, blood triglycerides, inflammatory markers, glucose and insulin resistance — all of which are risk factors for heart disease.
    • Cancer: Studies performed on animals suggest that irregular fasting may prevent cancer
    • Brain health: Intermittent fasting increases the cerebrum hormone BDNF . It might likewise protect against Alzheimer's disease.
    • Anti-aging: Intermittent fasting can expand life expectancy in rodents. Studies showed that fasted rodents lived 36–83% longer.

    Remember that studies are yet in the beginning phases. These studies were small, present short-term or conducted in animals.


    Fasting for Women

    There is some proof that intermittent fasting may not be as helpful for women as it is for men and sometimes it can be contraindicated. For instance, one study showed that it further improved insulin sensitivity in men, yet deteriorated glucose control in women. However human investigations on this subject are unavailable, studies in rodents have tracked down that intermediate fasting can make female rodents skinny, masculinized, infertile and cause them to miss periods. There are various narrative reports of women whose menstrual period stopped when they began doing intermittent fasting and returned to ordinary when they are back to their previous eating pattern. Therefore, women ought to be cautious with intermittent fasting.

    They should follow separate rules, such as stopping quickly if they have any issues like amenorrhea (absence of period). In the event that you have issues with infertility and additionally are trying to conceive, consider holding off on intermittent fasting. This eating pattern is additionally a bad idea in case you're pregnant or breastfeeding. Also it is contraindicated in people with a history of eating disorders or people who are underweight.


    Side effects of Intermittent Fasting

    The main side effect of fasting is hunger, however you may also feel weak and your brain might not perform as usually. This is usually temporary, until your body adjusts to these new changes in the eating pattern. In the event that you have a disease, you should talk with your primary care physician prior to attempting irregular fasting. This is especially significant in case of:

    • Diabetes.
    • Issues with blood sugar regulation.
    • Low pulse. 
    • Take drugs. 
    • Underweight.
    • History of dietary issues.
    • Woman trying to conceive. 
    • Woman with a history of amenorrhea. 
    • Pregnancy or breastfeeding. 

    All that being said, discontinuous fasting has an exceptional security profile. There isn't anything dangerous about not eating for some time in case you're solid and well-nourished in general.


    The science behind Intermittent Fasting

    In a well-fed stage, the individual cell in your body is in "development" mode. Its insulin signaling and mTOR pathways that advise the cell to develop, divide and synthesize proteins that are dynamic. Incidentally, these pathways, when overactive, have suggestions in cancer development.The mammalian target of rapamycin or mTOR has a high affinity for nutrients, particularly for sugars and proteins. At the point when dynamic, mTOR advises the cell not to waste time with autophagy ("self-eating"), a reusing and cleanup measure that rids your cells and body of damaged and misfolded proteins, for instance. The well-fed cell isn't stressed over being proficient and reusing its segments – it's busy dividing and growing.In a well-fed stage, your cells and their parts are profoundly acetylated. This implies that different molecules in your cells, including the "packaging" proteins called histones that wrap your DNA up inside the center of your cells, are bonded with acetyl groups on their lysine (amino acid) residues. What you truly need to know is that the well-fed cell has numerous genes, incorporating those related with cell survival and multiplication, turned on. This is on the grounds that acetylation will in general release the packaging proteins that typically keep your DNA wrapped up, and leaves your DNA alone to be read for protein creation.

    While your cells turn on cell development and division genes when you're not fasting, they likewise turn different genes off. These incorporate genes pertaining to fat digestion, stress resistance and harm repair. As a matter of fact, with intermittent fasting a portion of your fat gets transformed into ketone bodies that seem to reactivate these genes, leading to brought down irritation and stress resistance in the brain, for instance. Be that as it may, during starvation, things are altogether different. At the point when you practice intermittent fasting, your body responds to what it's anything but an environmental stress (low food accessibility) by changing the expression of genes that are significant in shielding you from stress.

    We have a very much safeguarded starvation "program" that kicks our cell into a totally distinct state when food, especially glucose or sugar, isn't anywhere near. With intermediate fasting and exercise, you initiate the AMPK signaling pathway. AMPK or 5′ AMP-activated protein kinase is the brake to mTOR's activity. AMPK signals the cell to go into self-defensive mode, initiating autophagy and fat breakdown. It represses mTOR. Simultaneously, while you are fasting the levels of a molecule called NAD+ start to rise since you don't have the dietary proteins and sugars that typically convert NAD+ to NADH through the Krebs cycle. NAD+, a molecule whose precursor is Vitamin B3, activates the sirtuins, SIRT1 and SIRT3. These sirtuins are proteins that eliminate the acetyl groups previously discussed from histones and different proteins. In this interaction, the sirtuins silence genes related to cell proliferation and activate proteins engaged with making new mitochondria (the force producing factories of your cells) and tidying up reactive oxygen species.

    Ketones, likewise delivered during fasting, fill in as deacetylase inhibitors (or keeping acetyl groups set up). This turns on genes related to antioxidant processes and damage fix.


    Does Intermittent Fasting lead to Ketosis?

    By 12 hours of fasting, you have entered the metabolic state called ketosis. In this state, your body begins to break down and consume fat. A portion of this fat is utilized by the liver to make ketone bodies (ketones). The two primary ketones, acetoacetate and β-hydroxybutyrate (BHB), fill in as an elective fuel hotspot for the cells of your heart, skeletal muscle, and brain, when glucose is not available and accessible. During intermittent fasting, ketone bodies created by your liver, mostly swap glucose as fuel for your brain as well as for different organs. This ketone utilization by your cerebrum is one reason that intermediate fasting is frequently thought to advance mental clearness and positive temperament – ketones produce less inflammatory products and they can even launch production of the brain growth factor BDNF. Ketones have likewise been displayed to diminish cell damage and cell death in neurons and can likewise decrease inflammation in other cell types.

    By 18 hours, you've changed to fat-consuming mode and are producing a large number of ketone bodies. You would now be able to start to measure blood ketone levels over your baseline values. Under ordinary conditions, the concentration of ketones in your blood ranges somewhere between 0.05 and 0.1 mM. At the point when you fast or restrict the nutrients in your eating regimen, this concentration can reach even 5-7 mM. You can assist with speeding up ketone creation with some heart-pumping exercise! For instance, intermittent fasting combined with running causes rewiring of nerve cells in the brain which prompts further developed learning and memory in lab animals. As their level in your circulatory system rises, ketones can go about as signaling molecules, like hormones, to advise your body to increase stress-busting pathways that decrease inflammation and fix harmed DNA for instance.


    What happens after 24 hours of fasting?

    What happens after 24 hours of fasting?

    Within 24 hours, your cells are progressively reusing old segments and breaking down misfolded proteins connected to Alzheimer's and different diseases. This is a cycle called autophagy.

    Autophagy is a significant interaction for cell and tissue revival – it eliminates harmed cell segments including misfolded proteins. At the point when your cells can't or don't start autophagy, terrible things occur, including neurodegenerative diseases, which appear to be caused by the diminished autophagy that happens during maturing. Intermediate fasting actuates the AMPK signaling pathway and represses mTOR movement, which thus enacts autophagy. However, this begins to happen when you considerably drain your glucose stores and your insulin levels start to drop. Irregular fasting is one manner by which you can increment autophagy in your cells and eventually decrease the impacts of aging. A recent report with 11 overweight grown-ups who just ate between 8 am and 2 pm showed expanded markers of autophagy in their blood in the wake of fasting for around 18 hours, in contrast with control members who just abstained for 12 hours. A subsequent report identified autophagy in human neutrophils beginning at 24 hours of fasting. In a third report, skeletal muscle biopsies of sound male volunteers who abstained for 72 hours showed diminished mTOR and increased autophagy. In mice deprived of food, autophagy increases following 24 hours and this impact is amplified in cells of the liver and brain after 48 hours. However, intermittent fasting isn't the best way to improve the capacity of your cells to reuse old segments, as some of the known advantages of physical activity for general wellbeing have to do with increased autophagy. For instance, autophagy incited by working out postpones the progression of heart disease by giving the heart better quality cell parts and lessening oxidative harm. Exercise, very much like intermittent fasting, inactivates mTOR, which increases autophagy in numerous tissues. Exercise acts similarly regarding the impacts of going without nourishment for an extended period of time. It activates AMPK as well as autophagy-related genes and proteins. In mice, endurance exercise increases autophagy in the heart, liver, pancreas, fat tissue, and brain, whereas in people, autophagy increases during high intensity work out, including marathon running and cycling.

    By 48 hours without calories or with not very many calories, carbs or protein, your growth hormone level is up to 5 times as high as when you started fasting.

    By 54 hours, your insulin has dropped to its most reduced level point since you began fasting and your body is turning out to be progressively insulin-sensitive.

    Bringing down your insulin levels through intermittent fasting has a scope of medical advantages both short term and long term. Brought down insulin levels put a brake on the insulin and mTOR signaling pathways, initiating autophagy. Brought down insulin levels can diminish inflammation, make you more insulin sensitive(and additionally less insulin resistant, which is particularly good if you are at an increased risk for developing diabetes) and shield you from chronic diseases of aging including cancer.



    Indeed, even a solitary fasting interval in people (e.g., overnight) can lessen basal concentrations of numerous metabolic biomarkers related with chronic illness, like insulin and glucose. For instance, patients are needed to fast for 8–12 hours before blood draws to accomplish steady-state fasting levels for some metabolic substrates and hormones. A significant clinical and logical inquiry is whether embracing a normal, intermittent fasting routine is a plausible and supportable population-based technique for improving metabolic wellbeing. Further controlled clinical examination is expected to test whether intermediate fasting regimens can supplement or replace energy restriction and, provided that this is true, regardless of whether they can facilitate long term metabolic improvements and body weight management.

    Furthermore, intermittent fasting regimens endeavor to decipher the constructive outcomes of fasting regimens in rodents and other mammals into reasonable eating patterns for decreasing the danger of chronic diseases in humans.

    This outline proposes that intermediate fasting regimens might be a promising way to deal with weight loss and working on metabolic wellbeing for individuals who can securely endure intervals of not eating, or eating practically nothing, for specific hours of the day, night, or days of the week. Whenever demonstrated to be viable, these eating regimens may offer promising non pharmacological ways to deal with further improving wellbeing at the population level with different health advantages.