Intermittent Fasting: What Is It and Is It Right for You?

Everyone seems to be talking about intermittent fasting these days, claiming it works wonders, even for those who've tried everything else with no success. So, what exactly is intermittent fasting, what are its different types, its benefits, and who should avoid it? Let's delve into it!

Intermittent fasting (IF) is a dietary regimen in which a person consumes minimal energy during specific time intervals and eats normally during others.

Intermittent fasting comes in several forms:

Alternate-Day Fasting: On "feast days," you eat normally or even slightly above your usual calorie intake. On "fast days," you either abstain from food for 24 hours or limit calorie intake to 25% or less. This type of fasting doesn't necessarily restrict overall calorie consumption but changes the frequency of meals. 

Time-Restricted Fasting: This approach allows eating only during a specific time window, typically 3-12 hours per day. The most popular pattern is the 16:8 method, involving 16 hours of fasting and an 8-hour eating window.

Modified Fasting: In this variation, you consume 25% or 50% of your required daily calories or skip food entirely for 1-2 days per week.

Fasting-Mimicking Diet: This five-day eating plan is repeated once a month for three months, consisting of 1,100 calories on the first day and 750 calories on the second through fifth days. During the rest of the month, you eat freely.

It's essential to remember that when you do eat, you should still meet your daily caloric needs and avoid exceeding them.

IF vs Calorie-restricted diet.

A traditional calorie-restricted diet involves reducing daily calorie levels to 50-70% of normal levels over a prolonged time. You will certainly lose weight on such a diet, but it is not easy to keep it for a long time.  The effectiveness of a long-term calorie restriction diet is 40% lower than interval fasting.

Interval fasting (IF) and obesity.

Nearly one-third of the world's total population is obese.

Interval fasting is effective in combating obesity and reducing the risk of obesity-related metabolic diseases and age-related diseases, as well as improving health outcomes in healthy individuals and patients with chronic diseases.

Recent scientific studies have shown that IF can prevent oxidative stress and adverse metabolic disorders in obese patients without diabetes.

IF and associated weight loss can influence the reduction of blood glucose, leptin, TNF-α and insulin-like growth factor-1 (IGF-1) levels.

Experiments have proven that IF improves the formation of new blood vessels and also improves insulin sensitivity in obesity.

IF in type 2 diabetes.

In type 2 diabetes, blood glucose levels are elevated, glucose is not delivered to the body's cells, and insulin levels are also lowered. This condition is called insulin resistance

IF promotes glucose uptake by organ tissues and increases the ability to store glucose in the liver and muscles as glycogen. During fasting, the liver maintains blood glucose levels.

IF and cancer.

Recent studies have shown that being overweight and obese is associated with a higher risk of developing adenocarcinoma of the esophagus, thyroid, pancreas, colon, rectum, endometrium, prostate, gallbladder, ovaries and breast, and multiple myeloma.

Tumor cells need a lot of nutrients - glucose, amino acids - to grow. Because IF reduces circulating glucose and amino acids, cancer cell growth is inhibited.

IF helps fight cancer by activating autophagy in malignant cancer cells.

IF in aging.

Over the last century we have begun to live almost twice as long, but this has led to an increase in the prevalence of age-related diseases such as neurodegenerative diseases, cardiovascular disease, diabetes, arthritis and cancer. Studies have shown that IF increases the average lifespan of rats by 14-45% and mice by only 4-27% .

IF improves brain function and reduces oxidative stress in middle-aged adults. Signaling pathways regulated by nutrient intake are dysfunctional during IF, leading to a halt in cell division and activation of stress factors, thereby slowing aging. IF can also protect the heart from ischemic heart disease by increasing growth hormone levels.

IF improves heart health, benefits circadian rhythm and has anti-aging effects. Long-term IF alters intestinal flora and slows the development of atherosclerosis.

IF in biological clocks and metabolism.

The molecular and biological clocks play an important role in how our body regulates nutrition and energy. Activity-rest and nutrition-hunger cycles coordinate metabolic processes. These clocks work like an internal clock in our body, helping us know when to eat and when to rest.

These pathways are in turn regulated by the timing of meals. 

If we eat in the evening, after 8 pm, and if our dinner has carbohydrates in it, insulin will work in our blood to process the glucose during the night, and not finding somewhere to use it up during the night, will deposit it as fat. But insulin is also an opponent of melatonin. So our sleep will be patchy and intermittent, and we will not have the deep phase of sleep in which our lymphatic system is supposed to remove toxins and harmful substances, for example from the brain, but will be busy eliminating fat.

Melatonin also switches mitochondria from getting energy from glucose to getting energy from fat.

IF increases fat oxidation and decreases the oxidative metabolism of carbohydrates without changing energy expenditure.

With IF, our circadian rhythms are normalized, we sleep deeply and do not interfere with our metabolism - getting rid of fat and toxins during deep sleep.

Who wouldn't benefit from Intermittent Fasting (IF)?

Those suffering from cardiovascular diseases.

Those who have endocrine system disorders.  In experiments on mice with impaired glucose metabolism, IF leads to increased death of pancreatic cells responsible for insulin production, increased insulin secretion, and increased production of free radicals. Hypoglycemia - low blood sugar, ketoacidosis, dehydration, low blood pressure and thrombosis are observed in diabetic patients during IF. On the other hand, in aged obese rats, prolonged IF alters the intestinal microbiome, improves lipid levels and stops weight gain, but increases blood glucose levels and decreases glucose tolerance.

How IF affects the reproductive system.

Those who are planning to get pregnant should not follow IF. It causes anorexia nervosa, which turns into infertility due to malnutrition.

Negative effects and limitations of IF in other systems.

IF promotes greater accumulation of triacylglycerides in white adipose tissues by increasing the expression of genes related to lipid storage.

In the elderly, regular physical activity during Ramadan (this is by the way a model for studying the effects of IF on the human body) improves mental performance but causes deterioration in sleep quality.

Those who have problems with the gallbladder, biliary secretion, who have gallstones - IF should be carried out under the supervision of a doctor. However, there are some general recommendations - consume choleretic foods - bitters. The gallbladder responds to the ingestion of bitterness in the small intestine. A cup of unsweetened black coffee has a choleretic effect. During the day you can drink choleretic teas and choleretic herbal infusions.

IF has a higher level of adherence than Calorie Restriction (CR). Not only is it an alternative to CR to reduce obesity symptoms, but it is a non-drug treatment that can increase life expectancy and importantly improve quality of life in old age.