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Intermittent Fasting- how to do it, benefits and Side effects

This post is also available in: हिन्दी (Hindi)

What is intermittent fasting?

Fasting has always been a significant part of the human lifestyle, since the early ages. Due to the scarcity of food, famine, or a failed hunting attempt, humans would have to stay without food for a prolonged period of time.

intermittent fasting

A more recently adopted version of fasting has however become highly recognized and is being practiced by a large number of people, which involves eating and fasting in a predetermined period of time and is referred to as Intermittent Fasting(IF). Intermittent fasting is not a variety of diet, but it resembles more closely to an eating habit. Following a routine of fasting with regular intervals for eating is what Intermittent Fasting is all about.

Many religions have practices of intermittent fasting, like following a fasting period of 9 days period of fasting in Navratra in Hindus, 1 month during Ramadan, or the 40-day fasting for Christians called lent.

It is also regarded as helpful in managing weight and lifestyle issues as well as certain diseases. The majority of people following this plan, do so to achieve the desired weight reduction and to maintain a healthy lifestyle.

How one can do intermittent fasting?

There are several different types of schedules that can be followed to perform Intermittent Fasting, and they are mentioned below.


16/8 technique

It is one of the commonest methods associated with fasting and includes

• Fasting period of 14-16 hours, followed by,

• Eating period of 8-10 hours.

Fasting period: When sleeping, one is technically fasting for the entire duration of sleep, and this can be extended by skipping breakfast and consuming lunch as their first meal. This is what makes the 16/8 method a little easier to follow compared to the other methods.

Eating period: The 8-hour eating window can be chosen according to individual preferences, but it is good to select a time slot before 9 p.m. as the body metabolism slows down in preparation for sleep. Following a 1 p.m. to 9 p.m. or a 12 noon to 8 p.m. window is often suggested to people following this technique.

In the period of 8 hours, one can opt to consume 2 or 3 meals. Eating healthy fresh food and avoiding junk food is always suggested.  Consuming beverage that doesn’t provide extra calories, which are sugar-free, like coffee, tea, or water can help reduce the feeling of hunger.


5:2 method

This method consists of

• Eating regular meals for 5 days in a week, followed by

• Fasting for 2 days a week.

The 2 days can be chosen based on individual preference. It is better to space the two days evenly throughout the week. During these two days calorie intake is restricted to less than 500-600 calories. This can be done by consuming two meals consisting of 200 and 300 calories. Drinking coffee or tea without sugar and water throughout the day is helpful.



This is another popular method that is fairly difficult to follow. It involves

• Fasting for a period of 24 hours, once or twice a week, followed by

• Regular meal consumption on other days.

One can opt to fast after any meal, from breakfast, lunch, or dinner, but a period of 24 hours of no food consumption needs to be maintained. Consuming liquids is allowed, including coffee or tea, without sugar, but solid food is restricted.

Since it is fairly tough to start with a 24-hour fast period, people are usually advised to follow the 16/8 technique and slowly increase the fasting time to 24 hours.


Alternate Day Fasting

This is similar to the eat-stop-eat version of intermittent fasting, but it involves

• Fasting every alternate day for either a period of 24 hours or restricting calorie consumption to 500-600 calories.

• Eating regular meals on every other day

Following a 24-hour fasting period without consuming solid food every other day can prove to be rather punishing, and one might have to sleep with the feeling of hunger. Limiting the diet to 500-600 calories can be a good start till one gets used to the schedule.


Meal Skipping

This includes impulsively skipping meals based on one’s own preference. Any meal can be skipped during a typical day.

It doesn’t emphasize on following a timely fasting but provides the liberty to skip a meal when one isn’t feeling hungry or doesn’t want to consume a meal. After skipping a meal, one can follow by consuming a healthier meal.


Warrior meal

This plan consists of:

• Heavy eating for a window period of 4-hour focused mainly on eating vegetables and fruits.

• Fasting for a period of 20 hours

It is similar to the 16/8 technique but provides a shorter window of time to consume meals and higher fasting periods.

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What happens when you do Intermittent Fasting?

• Our body works on glucose as the primary source of energy. When we consume food, it gets digested, and the gut converts the food to glucose, which is absorbed by the blood and delivered to various parts of the body.

• When there is an excess amount of glucose, it gets stored as fat in the body and as glycogen in the liver to be used later when the body runs out of food.

• When fasting, the liver uses its glycogen reserves to provide the body with glucose, and it takes about 11-12 hours for an inactive person to use up this reserve.

• Once consumed, the body then switches to another source of fuel, fat, which gets converted to ketones, which is then supplied to the body.

• This stage is called ketosis and can be achieved by fasting or consuming a ketogenic diet, which restricts the amount of carbohydrates.

• This conversion helps to reduce body weight by consuming the stored fat in the body and also promotes a healthy brain and body function.

How does Intermittent Fasting benefits your body?

intermittent fasting benefits

It may seem confusing how devoiding your body of food can help you to achieve better health. This becomes more difficult to understand when a person has to do strict fasting for several hours to even days. However, there are a number of studies conducted that have shown beneficial effects of fasting on not just losing the extra weight but also achieving better health with reduced risk of a number of lifestyle diseases.

Some of the benefits backed by researches are given below:


Weight Loss

People mostly perform intermittent fasting because it is a powerful tool to lose weight.

It starves the body of the glucose reserves, which make the body burn fat for fuel to supply energy. Insulin levels are reduced when fasting, which also accompanies fat consumption.

Calorie deficit: Consuming less than required calories every day results in a calorie deficit, which means that body is receiving fewer calories than it needs per day. This deficiency of calories leads to the consumption of stored reserves, aiding the process of weight reduction. Skipping one meal, say breakfast, can cut short the calorie intake by 20-30%.

Increased metabolism: Research shows that fasting increases the rate of metabolism helping you lose weight even when you are not doing anything. This is found to occur due to an increase in levels of norepinephrine, which is a fat-burning hormone.

Full day fasting showed a reduction of body weight by 3-9% and cholesterol by 5-20% in a matter of 12-24 weeks.

Another study revealed a better rate of muscle preservation was achieved while performing intermittent fasting compared to a regular calorie-restricted diet.



Intermittent fasting also helps in managing diabetes in the following ways:

Reduces insulin and blood sugar levels: It reduces the fasting insulin level by 57% or more.

Reduces weight: Obesity is one of the major risk factors associated with diabetes and insulin resistance. Thus, by removing extra weight intermittent fasting helps in managing diabetes.


Human Growth Hormone

Human Growth Hormone is linked to growth, cell regeneration, and cell reproduction in humans. An increase in height during childhood and an increase in muscle mass in adulthood is linked to this hormone.

Studies show an increase in the amount of Growth Hormone in the body within a 24-hour period of fasting. A two-day fasting also showed a higher secretion of this hormone, which was 5-fold compared to people who followed a regular diet.


Brain Function

There is limited research done on humans that studies the effect of intermittent fasting over brain function. However, It is a known fact that fasting induces the production of ketones, which is considered as good for brain function.

Improved brain functionStudies on mice who were on intermittent fasting have shown an improved brain structure and function.

Protection against nerve damage: Another study showed intermittent fasting provided protection against nerve damage, thereby reducing the chances of age-related complications like Alzheimer’s disease, in mice.

Improved learning and memory capacity: An increase in the production of brain-derived neurotrophic factor (BDNF) was observed in rats, which improves learning and memory capacity. This study in rats also suggested an increase in the number of newly generated neural cells.


Reduces Inflammation

• Inflammation is linked to a number of disease and conditions that affects the human body. Fasting, however, has shown a considerable decrease in the level of inflammation in the body.

Reduced inflammation rate: Studies conducted on 50 humans, before, during, and after Ramadan fasting, showed a reduced inflammation rate during the period of fasting.

Lower risk for cardiovascular diseases: Another study conducted before, during, and after Ramadan in 40 people showed reduced inflammation and lower risk for cardiovascular diseases.


Heart Health

Excess fat in the body is associated with high cholesterol levels which are in turn related to major diseases related to the heart. Intermittent fasting reduces the cholesterol levels as well as improves heart health.

Reduced cholesterol levels: it has been shown that intermittent fasting causes a 25% reduction in bad cholesterol (LDL) and a 32% reduction in triglyceride levels. Both of the above factors are directly linked to an increased risk of heart damage.

Reduced risk factors for heart disease:  A study with 110 people following intermittent fasting concluded with the people having lower blood pressure, lower levels of cholesterol, reduced weight, and an increase in insulin sensitivity.



Although most of the studies are still conducted on animals, a human trial may prove beneficial considering the positive results from rats.

Increased age span and growth: rats who were subjected to an intermittent fasting diet, showed an increase in the average life span by 83% and an increased growth duration by 75% compared to the ones following a regular diet.



Intermittent fasting may also show a reduction in the growth of tumor cells and thereby aiding the progress of healing in cancer patients.

• Studies conducted in rats showed a higher rate of survival in rats that were on an intermittent fasting plan than those who followed a regular diet.

• Although the studies are conducted on animals or cells, a positive result in curbing cancer growth provides a chance of a similar effect in humans as well.

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Are there any side effects and precautions to be taken?

Intermittent fasting isn’t meant for everybody and may pose difficulties in people who are on medication or have other physical health issues. It is always advisable to consult a doctor before starting a fast.

Some people who should take advice or be cautious before starting a fast include:

• People with low blood sugar or problem in regulating blood sugar levels

Diabetes patients, especially if you are consuming medicines for the same

• Underweight or malnourished people

• Patients with low blood pressure

• Someone who is consuming any medicine

• People having eating disorders

• Women who are trying to conceive

• Women with a history of menstrual issues such as amenorrhea

• Pregnant or breastfeeding females

• Kids under the age of 18

• Adults over the age of 60


Although people who opt for fasting might face some issues like improper brain function or reduction in concentration and low energy reserves, it is usually because of a new eating plan and the body trying to adjust to this new plan. It tends to fade away once the body adapts to the new routine, and it becomes much easier to stick to the plan.

One of the main concerns or side-effects that can be associated with intermittent fasting is hunger, which is difficult to manage, being on a calorie deficient diet and trying to control the food intake. However, with regularity in fasting, the body adapts to the cycle and staying hungry or skipping a meal becomes easier.

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What are the things you can do to manage the fasting better?

A few other things that one might have to be conscious about include:

• Staying hydrated and consuming the adequate amount of water.

• Consuming nutrient-rich diet during the eating period. As the eating window is limited, there are higher chances of nutrient deficiency when the following fasting for a longer period of time. Therefore, it becomes essential that one consumes food rich in vitamins and minerals to avoid deficiency.

Avoid eating junk food and keeping an eye on the calorie intake. During the period of eating in intermittent fasting, you may tend to eat more than required or consume fast foods. This practice can do more harm than good and you may never achieve your desired goals. So it is essential to watch what you eat and how you eat to get the best out of intermittent fasting.


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