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We often hear of the word ‘fasting’, but what does it really mean? By definition, fasting means ‘to eat sparingly or abstain from eating certain foods’. We have been hearing a lot about intermittent fasting, but let’s first understand what fasting is!
Fasting is practised by all religions and communities. In fact, medical fasting dates back to as early as the 5th century BC, when Hippocrates (a Greek physician), suggested abstaining from certain foods and drinks to certain patients, so that the body could heal itself.
There are various kinds of fasting:
- Complete alternate day fasting: This regimen involves alternating fasting days (no energy-containing foods or beverages consumed) with eating days (foods and beverages consumed ad-libitum).
- Modified fasting regimen: Modified regimens allow for the consumption of 20–25% of energy needs on scheduled fasting days. This regimen is the basis for the popular 5:2 diet, which involves severe energy restriction for two non-consecutive days a week, and ad libitum eating the other five days.
- Time-restricted fasting: These protocols allow individuals to consume ad libitum energy intake within specific windows, which induces fasting periods on a routine basis.
- Religious fasting: A wide variety of fasting regimens are undertaken for religious or spiritual purposes.
- Ramadan/Ramzan fasting: A fast from dawn to sunset during the holy months of Ramadan. The most common dietary practice is to consume one large meal after sunset and one lighter meal before dawn. Therefore, the fast and feast periods of Ramadan are approximately 12 hours in length.
Modern medicine also practices fasting in the form of “NPO” or “Nil per Oral” prior to surgery, post-surgery, or for patient’s to whom feeding could be counterproductive.
In recent times there is a new type of fasting that has come around, and that is ‘intermittent fasting’. This is not a very new concept. It has been around since 1915, and was originally explored as a possible way to treat obesity, and prepare patients for bariatric surgery. However, it was not very popular with the common man; the currently commonly followed form of intermittent fasting only gained popularity after 2012, after it was started in the United Kingdom, and later on in Australia.
What is intermittent fasting?
Intermittent fasting is the voluntary abstinence or avoidance of food and drink, for short periods of time. It is a dietary pattern where you follow cycles of eating and fasting.
There are different types of intermittent fasting:
- 5:2 fasting: In this type of fasting, a person eats normally five days in a week, and the other two are days of complete fasting (usually interspersed during the period of normal eating).
- Alternate-day fasting: In this type of fasting, a person eats normally one day, and the next day is a day of complete fasting or a severely restricted diet (usually less than 500-600 kcal).
- Daily time restricted fasting: This type of fasting involves eating normally for 8-10 hours, and then fasting (with the exception of water, and non-caloric beverages).
It has been seen that intermittent fasting has effects on:
Circadian biology: The human circadian rhythm regulates eating, sleeping, hormones, physiologic processes, and coordinates metabolism and energetics. All organisms follow a circadian or biological clock. This biological clock is what tells us to wake up in the morning, and go to sleep at night. It is also because of this biological clock that several bodily processes continue to happen, such as the process of hormone secretions, which trigger sensations of hunger, sleep, etc. This, in turn, has an effect on energy metabolism, and weight regulation in the body. In humans, research points towards a disrupted circadian rhythm increasing the risk of obesity, diabetes, cardiovascular disease, cancer, etc.
Gut-intestinal microbiota: Gut microbiota are the vast and diverse microbial community, which is present in our intestinal tract. These microbial colonies are responsible for helping with digestion, and a host of other functions. The gut microbiota also functions according to our circadian rhythms, wherein when we are awake and eating, it is found to be more active, especially during the day, rather than in the evening or when a person fasts.
Studies suggest that people who have a chronically disturbed circadian rhythm (people working on a night shift for extended periods, etc.), do show alterations in the gut microbiota, which can impair or disturb metabolism and thereby health.
What does intermittent fasting involve?
As the term suggests intermittent fasting involves periods of eating and fasting. It is usually practiced as 8:16 or 10:14, wherein the person eats for 8-10 hours (depending on the type of fasting), and the other 14-16 hours are spent fasting (not consuming food).
All forms of intermittent fasting involve eating a normal diet, preferably one that is rich in protein, and fibre, and low in carbohydrates and fats. During the period of fasting you are allowed to consume non-energy rich liquids, such as water, flavoured/infused waters, green tea etc. Milk, tender coconut water, fruit juices, etc. are prohibited, as they provide glucose and energy when they are broken down by the body. It is also important to note that during this time you should avoid consuming processed, packaged and fried foods, as they can have pro-inflammatory agents, which could derail the benefits that you attain from the periods of fasting.
Benefits of intermittent fasting:
Some of the benefits of intermittent fasting are as follows:
- Weight loss: Intermittent fasting has been seen to cause weight loss, as there is a restriction on the amount of calories being eaten. When coupled with a high-protein and high-fibre diet, it promotes fat to be broken down to release energy for bodily functions.
- Thinking and memory: Some studies say that it promotes memory, and possibly thinking and concentration in human beings.
- Heart health: Intermittent fasting has been shown to lower blood pressure levels, and improve overall heart health, possibly lowering the risk for cardiovascular diseases, and heart attacks.
- Physical performance: This type of fasting has been shown to promote fat loss, without causing any muscle damage. When coupled with regular/daily exercise, it can promote muscle building. This also promotes tissue health, and could be beneficial for people planning for surgery.
- Diabetes and obesity: People who are at risk of diabetes, or/and obesity, have been seen to improve their health with intermittent fasting; as it promotes weight loss, and fat breakdown to produce energy. It could also help with problems like sleep apnea and certain types of cancers that are commonly associated with obesity.
Contraindications to intermittent fasting
Intermittent fasting is not something that works well for everyone. It is contraindicated or discouraged for:
- Children and adolescents below 18 years, as they are still growing.
- Pregnant and lactating mothers, as it could impact foetal growth, and milk production and supply.
- Diabetic patients, with uncontrolled blood glucose values, as it could cause further derangement of these values.
- People with a history of eating disorders like anorexia nervosa, bulimia nervosa, etc, as it could further encourage these eating disorders.
- People suffering from severe gastritis, hyper acidity, GERD, etc, as this could worsen the condition and increase the discomfort felt, as a result of these conditions.
The last word
Intermittent fasting is the latest talk of the town, and is generally touted as an ‘easy’ diet that can be followed, resulting in weight loss, and other health benefits. However, it is not for everyone; some people who have tried out and follow intermittent fasting have complaints of nausea, hunger, anxiety, headaches and migraines, insomnia, etc. but most of them say that these complaints are transient and can be treated and managed with proper hydration.
Like any other major dietary or lifestyle change that you are about to embark upon, it is always best to consult a nutritionist or dietitian before starting something new. They can analyse your current diet and health status to determine whether this kind of dietary pattern or change will suit you or end up causing you more harm or discomfort.
