Intermittent Fasting and Lifestyle
In recent years, the increase in metabolic diseases and obesity has led scientific interest in researching the pathophysiology of human metabolism and the factors that influence it. At the root of the metabolic problem is a combination of innate and acquired factors, with lifestyle playing a decisive role in shaping our dietary choices, but also in their distribution during the day.
A particularly popular type of diet has emerged in recent years, that of intermittent fasting. This type can be easily adapted to the daily routine of a modern working person, while at the same time offering the freedom to consume favorite foods, even high-calorie ones, without hindering the achievement of weight loss. But is this particular way of losing weight as healthy as it is believed to be?
What is Intermittent Fasting?
Intermittent fasting (IF) is a type of fasting that includes two phases, the eating phase and the fasting phase. It should be noted that during the fasting phase, only calorie-free liquids are allowed, such as water, coffee, tea without milk or sugar, and other beverages.
There are 3 main fasting patterns:
- 16:8 This pattern involves eating within a specific time period, 8-10 hours during the day, for example between 12:00 and 20:00. Many people follow such a model without knowing it, due to living conditions and work hours.
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- 5:2 This pattern includes five days a week with a caloric intake equal to the dieter’s energy needs and two other days with a strict restriction of daily calories. For the two days, the reduction in energy intake is made by 70-75%. Thus, if a person consumes 2000 calories daily, for two days a week they should consume 400-500 calories.
- 1:1 In this pattern (Alternative – Day Fasting) there are days with free food consumption which alternate successively with fasting days. Fasting days may include only non-caloric beverages or, in the case of the modified type of diet, may include 20-25% of the individual’s daily caloric needs.
What are the advantages of Intermittent Fasting?
Metabolic Changes and Intermittent Fasting
Prolonged fasting is associated with reduced energy availability, resulting in the utilization of nutrients stored in the liver in the form of glycogen and in adipose tissue in the form of fat. This reduced availability causes a series of physiological hormonal changes. Specifically, it causes a decrease in insulin and an increase in cortisol. Low insulin levels encourage the breakdown of fat, which is the main fuel for energy production.
Regarding cortisol, although it increases sharply due to low glucose and the stress that the body experiences due to the reduced availability of energy, its levels return to normal relatively quickly. In fact, when intermittent fasting is applied for long periods of time, cortisol levels can even fall, resulting in better management of unpleasant situations that trigger stress and reducing the risk of developing diseases related to it.
Diabetes and Intermittent Fasting
The most interesting findings of this type of diet concern the effects on obese individuals with type 2 diabetes. The basic action of this pattern lies in ensuring sufficient fasting intervals to interrupt the vicious cycle of hyperinsulinemia and allow adipose tissue cells to be “deprived” of the presence of glucose and to begin the process of catabolism of their energy reserves. Studies therefore show that it affects glucose metabolism and insulin sensitivity. Consequently, patients experience lower blood glucose levels without increasing episodes of hypoglycemia. In addition, better insulin sensitivity implies less stress on the heart, reducing the risk of complications.
Cardiovascular Diseases and Intermittent Fasting
There is still insufficient data regarding cardiovascular diseases. However, research so far has shown that it protects the myocardium from cellular damage and inflammation caused by ischemia. In addition, it has a positive effect on the lipid profile, resulting in a decrease in the concentration of total cholesterol, triglycerides and LDL cholesterol. Based on the above, it follows that intermittent fasting could contribute to protecting the heart from damage.
Gastroenterological System and Intermittent Fasting
There is evidence that it may be beneficial for gut health, strengthening its microbiome. Recent studies show that 16:8 intermittent fasting leads to a change in the composition of the microbiome, increasing the production of “good” bacteria such as Lachnospiraceae, strengthening the natural barrier of the gut and reducing the risk of developing cancer and other inflammatory bowel diseases such as ulcerative colitis and Crohn’s disease.
Other diseases and Intermittent Fasting
The combination of calorie restriction with time restriction has shown positive effects on aging and memory as it promotes longevity and increases resistance to age-related diseases. In addition, it reduces the risk of neurodegenerative diseases e.g. Alzheimer’s disease. Studies that are still only conducted on mice have shown positive and very promising results in the treatment of cancer.
What are the disadvantages of Intermittent Fasting?
Nutrient deficiencies
Frequent and prolonged periods of fasting can eventually lead to the total or partial removal of food, leading to micronutrient deficiencies. Some of the most basic vitamin deficiencies associated with intermittent fasting are vitamin B12, D and E. A deficiency in important trace elements, such as iron and calcium, is also often observed. Therefore, it is important during feeding periods that meals are complete and the diet is balanced, without excluding food groups. This way, all the necessary nutrients are ensured.
Weight Loss and Intermittent Fasting
Weight loss in people who practice intermittent fasting does not seem to be greater compared to that of people who practice another hypocaloric diet. In fact, its implementation can make weight loss more difficult. This is because during periods of fasting, ghrelin, also known as the hunger hormone, increases while leptin, which is an anorectic hormone, decreases. This results in an increase in the feeling of hunger and a decrease in satiety, increasing the likelihood of consuming a larger amount of food. Over time, of course, and as intermittent fasting continues, the body adapts and both leptin and ghrelin levels stabilize, helping to better regulate food intake.
Reproductive Age and Intermittent Fasting
Intermittent fasting for long periods is not recommended for women, as it can disrupt the secretion of certain hormones such as estrogen, which can lead to menstrual irregularities, infertility, and other negative health effects.
Cardiovascular Disease and Intermittent Fasting
A recent study presented at the American Heart Association Congress found that people who practiced 16:8 intermittent fasting had a 91% higher chance of dying from cardiovascular disease compared to people who ate within 12-16 hours. Based on the above study, it seems that intermittent fasting may be harmful to health in the long term. However, the fact that the study is based on self-reports, has not been thoroughly tested for validity, and has not been officially published in a journal leads to the conclusion that the relationship between different patterns of intermittent fasting and the risk of developing and dying from cardiovascular disease should be studied further.
Gastroenterological System and Intermittent Fasting
The fasting hours suggested by this particular diet plan are likely to cause problems for people with gastritis, gastroesophageal reflux disease and irritable bowel syndrome. This is due to the fact that long-term fasting results in high secretion of gastric juice in the stomach, which due to its acidity can cause heartburn, bloating and negatively affect the intestinal flora, creating more intense symptoms of colitis. Therefore, people with gastritis, gastroesophageal reflux disease and stomach ulcers should avoid prolonged fasting, which will likely intensify the intensity of their symptoms.
Is intermittent fasting for everyone?
We must not forget that each person is unique and has different needs and habits, which is why individualization is important. Intermittent fasting, for example, could be applied to a person or athlete who aims to increase their muscle mass and who consumes sufficient amounts of protein, but it would be difficult to apply to a person who has been accustomed for years to eating many and frequent meals during the day, unlike someone who, due to a difficult routine, may not have time to eat or due to religious values. In addition, it is not recommended for some groups of people, such as pregnant women and people with a history of eating disorders. It is also important to mention that intermittent fasting is still under investigation as all results refer to studies of small groups and mainly in animals.
SOURCES
Malinowski, B., et al., 2019. Intermittent Fasting in Cardiovascular Disorders—An Overview, Nutrients, 11(3), p. 673. doi:10.3390/nu11030673.
Templeman, I., et al., 2021. A randomized controlled trial to isolate the effects of fasting and energy restriction on weight loss and metabolic health in lean adults. Sci Transl Med.
Stockman, M., et al., 2018. Intermittent Fasting: Is the Wait Worth the Weight? Curr Obes Rep.
Chrysostomou, S., Giannakou K., 2021. The effect of intermittent fasting on cancer prevention. Archives of Greek Medicine.
