Intermittent Fasting
Table of Contents
Intermittent fasting is a dietary regimen that has been popular for years. People most often choose this regimen to achieve better control over their body weight or to gain some of its health benefits. In the rest of the text, you can read about what intermittent fasting is, what different approaches exist, whether it is healthy, and what results it delivers.
Intermittent fasting encompasses a large number of different dietary regimens that share a common feature: food is not consumed during a certain window of time throughout the day, week, or month. The time periods during which food is not consumed, depending on the regimen, usually last between 12 and 48 hours, but there are also those that involve longer or shorter periods of fasting.
The idea behind intermittent fasting is to put the body into a state of increased stress, where it uses stored energy sources, like fat, due to a lack of or low caloric intake. While a state of increased stress sounds like something we would want to avoid, our body needs this type of condition to trigger stress response mechanisms that are not activated by everyday "minor" stress. It is believed that as a response to intermittent fasting, the body triggers an immune response resulting in the repair of damaged cells and the removal of metabolic waste products that linger in the body as a consequence of modern lifestyles.
Intermittent fasting, as a dietary regimen with periods of fasting, can lead to body weight loss and trigger an immune response in the body that contributes to cell repair and the removal of metabolic waste products.
Types of Intermittent Fasting
Although there are major differences among the types of intermittent fasting, they all share the same goal and achieve similar results. To choose the right type of intermittent fasting for you, seek professional help and consider which one you will be able to adhere to for the longest time, since significant results are noticed only after more than eight weeks.
16/8
In my experience, this is the most common and popular type of intermittent fasting. A lot of people have heard of or even tried this regimen in an attempt to regulate their body weight. It involves a relatively narrow eight-hour time window for food intake, followed by sixteen hours without caloric intake. It generally does not involve any restriction on food choices or calories during the eight hours within which food intake is permitted.
Early and delayed 16/8 diets are two forms that differ based on whether a meal is shifted or skipped entirely. With the early version, the eight-hour window begins almost immediately after waking up with breakfast. On the other hand, with the delayed version, breakfast is skipped completely and the eating window begins with the first meal closer to lunchtime. While daily obligations and habits are crucial for choosing the ideal way of eating, there is research indicating that meals consumed in the earlier part of the day offer more benefits.
Difficulty: Medium
12/12 or Overnight Fasting
Twelve hours during which you eat and twelve hours during which you do not eat is not a diet, but rather expected behavior that everyone should naturally follow. However, I was surprised by the number of people I have worked and talked with who consume food during their entire waking day—meaning within a window of 14 or even 16 hours.
This is one of the first steps I suggest to people struggling with body weight control. When you start with breakfast, look at the clock, remember or write down what time it is, and finish dinner by that same time in the evening. After that, do not consume anything except water or unsweetened tea. In this way, you give your body enough time to digest food before sleep and achieve better sleep quality. 12 hours without food intake will yield some of the effects of intermittent fasting, especially if you stick to this at least 6 days a week. Another good thing is that from a 12/12 regimen, it will be easier to transition to a diet with a longer fasting period, such as a 14/10 regimen.
Difficulty: Easy
18/6 and 20/4
These are regimens with a slightly more intense approach, where the time window for caloric intake is 6 or 4 hours. The effects of these dietary regimens are identical to others in the time-restricted eating group (16/8, 14/10, 12/12), but the results are visible faster and require greater mental discipline.
I do not recommend them often due to concerns about giving up, as well as a personal belief that more slowly achieved dietary effects yield longer-lasting positive results.
Difficulty: Hard
OMAD (One Meal A Day)
OMAD, or one meal a day, is the most extreme approach to time-restricted eating. As the name suggests, it involves only one meal during the day, lasting about an hour. This single meal needs to satisfy all the body's daily needs, so it must be abundant and varied. This kind of dietary regimen is ideal for people who have very little time to eat at home, as it completely eliminates the fast and unhealthy food they would otherwise eat. On the other hand, it requires discipline as well as a lot of sacrifice, because besides food, any caloric intake outside the one-hour window per day is forbidden on this regimen, which includes snacks, fruit, juices, alcohol, etc.
Difficulty: Very Hard
Spontaneous Meal Skipping
This is not a clearly structured dietary regimen, but rather a name for what most people occasionally do by accident. Some people believe they can achieve the benefits of intermittent fasting by skipping a meal during the day if they are not hungry or do not have time.
Skipping meals, especially randomly and unplanned, can have the opposite effect and lead to overeating during the next meal and consuming a higher number of calories. Spontaneous meal skipping is not something I suggest to people, and I believe that setting and sticking to a plan leads to better results. It should be mentioned that skipping a meal can have better results than consuming low-quality food, such as bakery products or fast food.
Difficulty: Easy
5:2
The 5:2 ratio refers to 2 days of fasting and 5 days of normal eating during the week. This dietary regimen is one of the most popular among all intermittent fasting plans and is relatively simple to follow. During the 5 days of normal eating, there is no calorie counting or restriction of specific foods, while during the 2 days of fasting, food is not completely eliminated. During the fast, an intake of 500 calories per day is anticipated for women, and 600 for men, and these calories can be consumed in one or multiple meals. Additionally, the fasting days do not have to be the same every week, so you can choose them based on your schedule, making sure you do not have two consecutive fasting days.
Difficulty: Medium
The Warrior Diet
This diet was designed and popularized by fitness expert and former Israeli special forces soldier Ori Hofmekler. It is most similar to the OMAD regimen and suggests one large meal, usually late in the day, during which any food can be eaten. However, during the earlier part of the day, unlike OMAD, a smaller intake of fresh fruits and vegetables, boiled eggs, or dairy products is advised.
In his book, Ori explains that by looking at historical data and scientific studies, one can conclude that to achieve health and a lean, strong body, it is best to mimic a classic warrior lifestyle, like the one ancient Greek and Roman warriors had. This lifestyle involves a lot of physical activity with little food during the day, followed by a large meal during the evening or night. It should be mentioned that, in his own words, this dietary regimen is not based on scientific or medical research but on his personal observation and belief.
Difficulty: Hard
Eat Stop Eat
Eat Stop Eat was promoted in the eponymous book by fitness expert Brad Pilon. It talks about a fasting period lasting 24 hours, once or twice a week, followed by days during which you eat normally. It is similar to the 5:2 regimen, but unlike it, there is absolutely no caloric intake during the fasting days. It is popular because of the absence of rules on days when food is consumed, although the recommendation is to eat normally—meaning to avoid overeating after the fast.
Difficulty: Hard
Alternate-Day Fasting or the 4:3 Regimen
This fast exists in two forms, but both involve a day of normal and healthy eating with 3 to 5 meals a day, followed by a fasting day. The difference in variations exists in the fasting day itself. While some nutrition experts suggest an intake of up to 500 calories or about 25% of daily needs, others advise a complete fast—meaning the intake of only calorie-free liquids on the fasting day, such as coffee, tea, and water.
Numerous studies have been conducted comparing the effects of alternate-day fasting to classic diets with daily calorie restriction. According to a review that encompassed a larger number of smaller studies, there is a significant difference in weight loss efficiency between these two approaches, and it showed that alternate-day fasting yields better results.
Difficulty: Hard
Extended Fasting
Extended fasting is the most demanding form of intermittent fasting since it involves periods without caloric intake that are longer than 24 hours. The most common form is a 48-hour fast, but there are people who practice regimens lasting between 4 and 21 days. In addition to hunger, an extra problem with this regimen is the dizziness and fatigue that occur due to a lack of carbohydrates and electrolytes, so it is not for everyone.
This is the regimen I follow, with fasts lasting between 33 and 48 hours, twice a month. In my experience, it is very grueling the first few times, but the body adapts after that, and subsequent fasts are mentally and physically easier. Additionally, I have found several tricks that can help, such as starting the fast after breakfast on the first day, consuming water with electrolytes, tea, or coffee in order to delay the feeling of hunger. Unlike other similar regimens, it does not involve fasting every week but only a few times a month, which suits me better.
Difficulty: Very Hard
Other Forms
In addition to the listed protocols, it is possible to find other regimens and experiences from people who have tried them. There are combinations of almost all the regimens mentioned so far, including spontaneously skipping multiple meals, planned meal skipping every other day, following an 8/16 or other time-restricted regimen a few times a week, and others. I would reiterate that there are no studies indicating greater or lesser effectiveness for any of these ways of eating, so the most important thing is to choose the one that suits you best and that you can continuously adhere to for as long as possible.
Benefits
Autophagy
The connection between intermittent fasting and autophagy is well-known even to people who are not familiar with the exact meaning of these terms. At the same time, autophagy is responsible for some of the potential health benefits of intermittent fasting, so for these reasons, I will briefly explain what autophagy is and why it is interesting.
The word autophagy comes from ancient Greek and can be translated as self-eating. This is a natural mechanism by which non-functional parts of the cell are destroyed and recycled. Non-functional parts of the cell can arise in various ways under the influence of external factors or natural mutations.
Autophagy or autophagocytosis happens constantly in our body, but it can be accelerated or slowed down. During periods of fasting, when there is no new caloric intake, the body turns to looking for energy within itself, so enhanced autophagy occurs. Additionally, since the body is not burdened with digesting newly consumed food, it turns to cleaning and maintenance, making fasting like a weekly house cleaning.
Over the last few decades, autophagy has attracted a lot of medical attention, as it has been shown to have a positive and/or negative impact on multiple disorders, including infections, inflammation, neurodegenerative, metabolic, and cardiovascular diseases, obesity, and different types of cancer.
Unfortunately, the connection between autophagy and various diseases is extremely complicated, and clear data on its exact impact does not yet exist. For example, multiple studies on animal models have proven the role of autophagy in preventing the formation of tumor cells by protecting cells from oxidative stress, DNA damage, inflammation, or the accumulation of non-functional organelles in the cell. However, the same has not been proven in humans, and additionally, a key role of autophagy in the survival and progression of tumor cells has been discovered, which has the opposite effects.
While further research is absolutely necessary, it has been proven that autophagy positively affects the body's response to chemotherapy, radiotherapy, and targeted therapy applied during cancer treatment by protecting normal cells from the toxic effects of these agents, which is why autophagy, or fasting, is being considered as an auxiliary therapy in tumor treatment.
Autophagy is a natural process that involves the digestion of bad parts of the cell. It can have a positive impact on cancer prevention, but more research is necessary.
Obesity
Six smaller studies compared the effects of intermittent fasting to a standard calorie-restricted diet and concluded that there are no major differences in the results achieved. It should be noted that all intermittent fasting regimens included healthy eating during non-fasting days, which meant a plant-based diet with a low sugar intake.
27 trials, mostly of shorter duration and with a smaller number of participants, indicated that intermittent fasting can be an effective way to control weight. Participants achieved weight loss between 0.8% and 13% over the course of 2 to 26 weeks of research duration. Some of the trials, which simultaneously tracked people on diets with restricted caloric intake, confirmed that there are no significant differences in effectiveness. While these data are not completely reliable, they point to promising effects of fasting.
Intermittent fasting can achieve confirmed results in attempts to reduce body weight, which are of similar effectiveness to diets with daily calorie restriction.
Insulin Resistance and Type 2 Diabetes
Fasting blood glucose levels are one of the main indicators of disorders in carbohydrate metabolism—meaning insulin resistance, which is a pre-condition for type 2 diabetes and a significant problem occurring in an increasing number of people in our country and the world. Because of this, controlling blood glucose levels represents one of the key tasks set before modern medicine. Finding an effective way to achieve this control is an area that is actively developing and being researched.
Eight separate studies reported the effectiveness of intermittent fasting in lowering glucose levels. Six studies applied only intermittent fasting regimens, while the other two additionally included daily training. No major difference was noticed between these two approaches, but both showed a significant reduction in fasting blood glucose levels.
A review of available literature from February 2020 confirmed, in most cases, the effectiveness of intermittent fasting as a non-medical approach in treating type 2 diabetes, lowering blood glucose and insulin levels, as well as reducing insulin and leptin resistance.
There is solid evidence regarding the positive effects of fasting on blood glucose and insulin levels.
Cardiovascular Diseases
Cardiovascular diseases are the leading cause of death in our country and the world. This is a group of heart and blood vessel diseases whose cause is not single. Intermittent fasting improves multiple factors that influence cardiovascular diseases, which has been proven in animal and human examples. Intermittent fasting positively affects blood pressure, heart rate, cholesterol levels, lipoproteins, triglycerides, as well as the previously mentioned glucose and insulin levels.
Intermittent fasting positively affects heart and blood vessel diseases.
Aging, Oxidative Stress, and Inflammatory Processes
A connection between intermittent fasting and aging has been established in humans and animals. However, a clear explanation for this connection is still being sought. One proposal is that fasting causes the production of protective molecules that protect our body from oxidative stress, as well as calming inflammatory processes that lead to faster tissue aging. The aging process itself is very complicated and numerous new discoveries await us, and the connection between periodic fasting and these processes is being intensively researched, but the studies I found included a very small number of participants or short time periods.
Fasting can have positive effects on reducing inflammation and oxidative stress, which consequently can result in slowing down aging.
Other Benefits
There is research on the positive effects of periodic fasting on other conditions and diseases, based on the impact of fasting on the same parameters that have already been mentioned. Reducing body weight, improving blood parameters, reducing oxidative stress, and alleviating inflammatory processes can lead to improvement in various diseases or conditions such as cancer, neurodegenerative disorders, asthma, multiple sclerosis, arthritis, surgical or ischemic tissue damage, psychological and cognitive disorders, and others. While the impact on some of these diseases or conditions is well researched, for others there is almost no research, and the entire field has yet to be applied in medical practice.
The impact and application of fasting in treating numerous diseases have yet to be fully researched.
Concerns
A frequent concern for people skeptical of intermittent fasting is muscle breakdown due to insufficient caloric and protein intake. However, this does not happen since there is no long window of time with food restriction. During the fasting period, a smaller percentage of muscle mass breakdown may occur, but growth hormone secretion increases simultaneously. When proteins become available again, growth hormone directs proteins toward rebuilding the muscles that were consumed during the fast, so permanent loss of muscle mass does not occur. Studies indicate that muscle mass is maintained when practicing periodic fasting, but they do not conclude whether it is possible to significantly increase muscle mass on this regimen.
Slowing of the basal metabolic rate is another common concern. Slowing of the basal metabolic rate practically means that in the absence of energy, the body begins to expend less. With chronic starvation lasting over several dozen days, reduced energy expenditure can persist for years or even decades. Such a metabolic change would be particularly undesirable for people trying to lose weight by practicing intermittent fasting. However, according to a large number of papers, this certainly does not happen with short-term fasts up to three days.
Some people's fear of losing muscle mass or slowing down their basal metabolic rate is not scientifically supported.
Side Effects
With any change in diet, some problems and side effects can occur, which is also the case with intermittent fasting. The most common and expected side effect is hunger, which can cause overeating after the fast. Other side effects can include headache and dizziness, nervousness and irritability, digestive and stool issues, fatigue and loss of energy, sleep and breath problems, and dehydration. Most of these problems can be prevented by adequate intake of electrolytes and fluids during the fast, and by gradually introducing food after it.
Intermittent fasting can cause transient side effects, but most can be mitigated by adequate hydration and gradual food introduction.
Risks
Intermittent fasting can lead to weight gain if the fast is followed by a large caloric intake during days when food intake is permitted. For this reason, meals should be well planned and limited. While I generally do not have problems with overeating, I have made the mistake several times of bringing practically everything out of the fridge after a fast and returning little to it. This caused feelings of bloating, nausea, and over-fullness. For this reason, my first meal after a fast consists of about 400 grams of cooked chicken breast, and I consume the second meal only 2 to 3 hours after that.
If you suffer or have suffered from an eating disorder, such as bulimia or anorexia, intermittent fasting is not for you. Any diet that includes skipping meals can trigger a disruption in your relationship with food and lead to an eating disorder.
People suffering from type 1 diabetes or taking medications for type 2 diabetes should not practice longer fasts, as a dangerous drop in blood glucose levels can occur.
Women who are pregnant or breastfeeding should not undergo restrictive dietary regimens due to increased energy needs and potential risks to the fetus.
Various medical conditions, such as fever, recent surgery, or other illnesses, as well as mental illnesses combined with restrictive dietary regimens, can pose additional risks and are not recommended.
Although intermittent fasting can be useful for body weight control, it is important to be cautious and avoid it in the case of certain health conditions or risks of eating disorders.
Conclusion
Some form of fasting has existed for more than three thousand years as part of religious or social practice. This was preceded by multi-millennial fasting caused by the environment and food scarcity, so periods without food intake have existed since humans have existed. We are the first or second generation of humans ever to have the luxury of everyday food on our plates. For this reason, it is not surprising that we evolutionarily developed the ability to survive without caloric intake over longer periods of time. While intermittent fasting and its potential positive impact have been known for several decades, we still do not have developed habits or prescribed procedures for practicing this type of fast.
It is surprising how many people I have talked and worked with stated that they could never survive a whole day without eating. My opinion is that everyone should adhere to one of the dietary regimens listed here to give the body time to clean up and achieve a longer and healthier life.
Some of the mentioned regimens are harder than others, but difficulty by no means speaks to effectiveness or the benefits that can be achieved. One should focus on choosing the regimen that suits you best and that you can stick to for practically your whole life.
Interestingly, while most regimens, in principle, imply daily adherence, research shows that this is not necessary. If you went out to town, went to a celebration, or just really wanted to eat outside the prescribed time window today, that is not a problem. The effects remain unchanged as long as you do not break the rules more often than two non-consecutive days a week. After a day when you could not or did not want to respect your chosen regimen, just continue as if nothing happened.
As always, I am at your disposal for all questions, advice, or suggestions, and you can read about other topics on my BLOG.