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Periodic Fasting - Its Significance and Application
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Intermittent fasting, which entails voluntarily abstaining from consuming food, has been practiced for ages. It was often linked with religious practices. In the present times, interest in fasting as a tool for health and maintaining one's figure is increasing. Recently, intermittent fasting has been gaining more and more popularity. But what does it actually signify and is it worth applying?
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What is interrupted fasting
Interrupted fasting is an alternative dietary model that involves limiting food intake to specific time frames, known as the nutritional window. One fasts for several hours each day or extends the fasting period to full days. During fasting, calorie intake is reduced from 60 to 100%. On non-fasting days, there are no restrictions on the amount of calories consumed.
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Alternating Fast Cycle
Fasting is not a single method, there are many types of fasting, for example: (alternate-day fasting) – requires a full-day fasting cycle in shifts with any amount of food consumed; (alternative-day modified fasting) – requires consuming a minimum of 60% fewer calories on fasting days than on non-fasting days; (intermittent energy fasting) – a calorie-restricted diet; (periodic fasting) – requires a fasting period of 2 to 21 days; (time-restricted feeding) – a time-restricted diet that limits the time of food consumption to 8–10 hours a day. The most popular approach is the 16/8 fasting, where the feeding window is 8 hours a day. This usually involves fasting after dinner and skipping breakfast the next day; (5:2 diet) – requires fasting for 2 days a week. On fasting days, a maximum of 500–600 kcal can be consumed. On the remaining days of the week, one eats normally.
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Fasting break - the underlying mechanisms
At the onset of the period of hunger, the glucose stores in the liver and muscles are released, enabling the body to function properly after a few hours, when these reserves are depleted, glucose is synthesized from free fatty acids, thus maintaining a constant level of blood sugar. Longer fasting leads to the initiation of the process of transforming free fatty acids into ketone bodies, which serve as an alternative energy source. Through these processes, the body is able to function during multi-hour periods of hunger and enable the degradation of excess fat tissue. Intermittent fasting has a positive impact on the entire body by reducing oxidative stress throughout the body (A. Michalsen, Ch. Li 2013). It improves the body's ability to cope with stress at the cellular level, making it less susceptible to aging processes and the development of many diseases. Intermittent fasting also has a positive impact on the digestive tract by giving it time to regenerate. The words of Socrates "We eat to live, not live to eat" help to better understand the concept of fasting. People need food to live, but in today's times, the statement "We live to eat" is closer. The modern lifestyle and the great availability of food, including snacks, lead to many people not even observing a one-hour break between meals. Eating is a fixed element of business and social meetings. However, each bite of food requires enormous work from the digestive tract. One should not fall into extremes, and too long breaks between meals can lead to an excessive drop in blood sugar levels, a decrease in concentration, resistance to stress, and a deterioration in well-being (A. Serwin 2021).
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Does a fasting break genuinely mean no restrictions? What can you consume?
During a fasting break, there are no restrictions. You can consume anything, but only within a specified food window. However, it is recommended to eat nutritious meals that provide all essential nutrients. It is also important to ensure adequate hydration during the fast, so it is advised to consume fluids that do not provide energy, such as water, unsweetened herbal teas, coffee, and tea.
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Intermittent Fasting and Its Impact on Health
Intermittent fasting can have a positive impact on human health, provided that a balanced and full-fledged diet is followed during the nutritional time window. Intermittent fasting has a beneficial effect on the body by reducing oxidative stress and activating the process of autophagy, which is the self-destruction of damaged cells (A. Michalsen, Ch. Li 2013). In addition, intermittent fasting is most commonly associated with a healthy insulin diet. All living organisms, including humans, function according to their circadian rhythm. The biological clock of humans is located in the hypothalamus and reacts to light stimuli. Digestion of breakfast is more efficient than digestion of dinner, and in the morning, a greater sensitivity of cells to insulin, better glucose tolerance, and higher thermogenesis of meals are observed compared to late evening hours (K. Kessler, O. Pivovarova-Ramich 2019). Eating according to this cycle leads to an improvement in metabolism and weight control. Nighttime eating disrupts the circadian rhythm, leading to many metabolic disorders. Studies by R. E. Patterson and colleagues confirm that eating in late night hours is associated with shorter and poorer sleep quality, which increases the risk of developing insulin resistance, diabetes, obesity, and heart-circulatory diseases, as well as cancer. Extending nighttime fasting to 14 hours can contribute to reducing calorie intake, which regulates weight control and improves sleep quality (S. Gill, S. Panda 2015). It turns out that intermittent fasting is an alternative treatment method for many metabolic disorders (V. D. Longo 2016). A diseased state is associated with an inflammatory state, which is a normal reaction of the immune system. Chronic inflammation can accompany heart diseases, diabetes, obesity, and cancer (P. Hunter 2012). According to a study published in Nutrition Research, 50 people who participated in Ramadan had lower levels of certain inflammation markers during fasting (M. E. Faris 2012). The same phenomenon was observed during extended nighttime fasting by the team of C. Marinac. M. P. Mattson and R. Wan showed that intermittent fasting improves the function of the cardiovascular and nervous systems by lowering blood pressure and increasing insulin sensitivity.
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Fasting breaks and weight reduction
Fasting breaks appear to be an attractive dietary pattern in the context of weight reduction. During fasting, the body receives no energy in the form of glucose and must mobilize reserves stored as liver and muscle glycogen. Once glucose is depleted, the body turns to adipose tissue, which is the primary goal for individuals with excess weight. In a 2019 meta-analysis by C. Rynders and colleagues, studies evaluating intermittent fasting breaks as an effective method for body weight reduction were examined. The meta-analysis included randomized trials lasting at least 8 weeks involving overweight individuals (BMI > 25 kg/m²) that compared fasting breaks to a traditional energy-restricted diet with daily caloric deficit. The majority of trials involved women with low physical activity levels. In 9 out of 11 reviewed studies, no significant differences in body weight or fat mass reduction were found between groups utilizing fasting breaks and those following a traditional low-calorie diet.
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Pauses in food consumption - the advantages
Pauses in food consumption have a variety of advantages: they do not require significant time commitment or work in the kitchen, nor do they require weighing food or denying oneself less healthy favorite snacks. Pauses in food consumption appear to be an effective method of weight loss. Furthermore, they improve the lipid parameters and insulin sensitivity of cells, contributing to the stabilization of the body's carbohydrate metabolism.
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Intermittent fasting - Disadvantages
Regrettably, intermittent fasting also has its downsides. Not everyone will be able to adhere to them because persistent hunger can occur during the fasting period. Moreover, very often after a prolonged period of fasting, there is a so-called "wolf hunger". This can lead to consuming too much food at once, which can cause gastrointestinal discomfort and contribute to exceeding the individual calorie requirement.
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Fasting breaks – who are they suitable for?
Fasting breaks may be utilized by adults who are in good health, possess normal body weight, overweight or obesity, as well as by athletes whose sporting disciplines necessitate a quick reduction in weight. Nevertheless, fasting breaks are not advisable for: children and adolescents, the elderly, pregnant and breastfeeding women, females with menstrual disorders, those suffering from diabetes, eating disorders such as anorexia or bulimia, individuals afflicted with cancer, kidney disease, liver disease, etc.
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Broken fast: How to get started?
If someone decides to fast, it is best to start with an extended period of night fasting. Some authors suggest that a good option is to give up breakfast at the start (J. B. Rives 2019). Then it is advisable to gradually shorten the eating period by one hour per week, for example by extending the time for lunch. When a feeling of hunger arises during fasting, it should not be ignored. It is a good idea to reach for a light cocktail, smoothie, or drink warm herbal beverages. After a certain period, the body will adapt to fasting and hunger will occur less frequently. Fasts lasting longer than 2 days should not be carried out on one's own, but under the supervision of a specialist. Intermittent fasting is a promising nutritional model that can serve as an effective tool for weight loss and health improvement. Already the night fast can have a positive effect on reducing the level of glucose and insulin in the blood, which can reduce the risk of insulin resistance and diabetes (R. E. Patterson, D. D. Sears 2017). However, there is still a lack of research on the long-term effects of its application.
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