Intermittent Fasting – Complete Guide 2021

Intermittent fasting (IF) is now a days one of the world’s most favoured health and fitness trend. It is used for improving health and lifestyle by loosing weight.

According to many studies it is proved that it has strong effects on your body and brain also it may even help you to delay your ageing and live longer and healthy.

What Is Intermittent Fasting (IF)?

Intermittent fasting (IF) is a pattern of eating that is repeats or cycles  between intervals of fasting and eating.

It doesn’t have any relation with the foods you should eat but rather with time  means when you should eat them.

conventionally it is not a diet but more precisely it is called as an eating pattern.

Common fasting methods include daily 16-hour of fast or fasting for 24 hours, two times in a week.

Fasting has been a practice from ancient times as during those days Ancient hunter-gatherers didn’t have enough food options available . Sometimes they couldn’t find anything to eat.

As a result, humans evolved to be able to function without food for large durations  of time.

Actually, fasting from time to time is more natural than always eating ( more than 3–4 meals in a day).

Fasting is also often done for religious or spiritual purposes, included in many religions

Methods of intermittent fasting:

There are lots of different ways of doing intermittent fasting — all of which suggest dividing the day or week into durations of eating and fasting.

During the fasting periods, you eat either in very small amount or nothing at all.

Some of the most popular methods are:

The 16/8 method: ( or the Leangains protocol), this method have skipping breakfast and limiting your daily eating period to 8 hours, (such as from 8am to 4pm) Then you fast for 16 hours in between.

Eat-Stop-Eat: This involves fasting for 24 hours, one or two times a week, like-  by not eating from lunch first day until lunch the next day.

The 5:2 diet: In this method, you limit the calories upto 500–600 calories on two non-consecutive days of the week, but eat normally the other 5 days.

By lowering your calorie intake, these  all methods should result in weight loss as long as you don’t compensate by eating too much  during the eating periods.

Among all these methods 16/19 method is most popular and people find it as the easiest and convenient method to follow.

How It Affects Your Cells and Hormone?

During fast, several cellular and molecular changes occurs in the body.
(Such as, endocrine changes,lipolisis , stress resistance etc

Cells also start repair processes and change the gene expression.

These are some changes that occur in the body during fast:

Human Growth Hormone (HGH): The level of growth hormone , increasing as much as 5-times. This can leads to fat loss and muscle gain.

Insulin: Insulin sensitivity improves and levels of insulin drop adequately. Decreased insulin levels make stored body fat easily available.

Cellular repair: During fasting,cells begin cellular repair processes like autophagy,  ( self eating-cells digest and remove old and dysfunctional proteins that build up inside cells).

Gene expression: There are changes in the genes function which are associated with  longevity or durability and protection against disease.

These changes in the cell function,harmone levels and gene expression are result in the all the health benefits of intermittent fasting.

Intermittent fasting is a very effective weight loss Tool

Weight loss is the most common reason for people to try intermittent fasting.

As intermittent fasting makes you take fewer meals,it can lead to an automatic decrease in calorie intake.

Also, it changes hormone levels to promote weight loss.

Additionally to, it inhances the release of fat burning hormone norepinephrine (noradrenaline).

Because of all these hormonal changes, short-term fasting may rise up the metabolic rate by 3.6–14%.

Because intermittent fasting makes you eat lesser and burn more calories,it causes weight loss by changing both sides of the calorie equation.

Studies show that intermittent fasting can be a very powerful weight loss tool.

In 2014 review study it is found that intermittent fasting can cause 3–8% weight loss in 3–24 weeks, which is a noticeable amount, compared to most weight loss studies.

According to the same study, people lost 4–7% of their waist circumference,which indicates a  loss of harmful  fat that builds up around your organs and causes so many diseases.

And according to another study it is suggested that it causes less muscle loss than the another methods of continuous calorie restrictions.

The main reason for the success of intermittent fasting is that it helps you eat fewer calories overall and If you eat in massive amounts during your eating periods, you may not going to lose any weight.

Health Benefits

There are so many studies have been done on intermittent fasting, in animals and humans.
And according to these studies it is shown that it can have tremendous benefits for weight control and the health of your body and brain. It may even increase the duration of life.


The main health benefits of intermittent fasting:

Weight loss: As written above, intermittent fasting is the simplest way to reduce weight l and belly fat without having to conscious calories restrictions

Insulin resistance: Intermittent fasting can lowers insulin resistance, decreasing blood sugar by 3–6% and fasting insulin levels by 20–31%, thus protects type 2 diabetes.

Inflammation: Some studies show decrease in  inflammatory markers.

Heart health: Intermittent fasting may lead to reduction of LDL cholesterol, blood triglycerides, inflammatory markers, blood sugar and insulin resistance( which are the risk factors for heart disease) thus protects from many cardiac diseases.

Cancer: Some animal studies shows that intermittent fasting may protect from cancer.

Brain health: Intermittent fasting increases the brain hormone BDNF(brain derived neurotrophic factor),  growth  generetion of new nerve cells. It may also prevents Alzheimer’s disease.

Anti-aging: Intermittent fasting  increase lifespan in rats. Studies suggested that fasted rats lived 36–83% longer.

It should be noted that research is still in it’s initial stages. Many of the studies were small, short-termed  or performed in animals.  There are so many things yet to be discovered and many questions still  unanswered in higher quality human studie.

Makes Your Healthy Lifestyle Simple

Eating healthy is easier but difficult to continue in long term.


Intermittent fasting gives a healthy and simpler lifestyle and makes things easier,
as there is no need

One of the main obstacles is all the work required to plan for and cook healthy meals.

Intermittent fasting can make things easier, as you don’t need to plan, cook or clean up after as many meals as before.

For this reason, intermittent fasting is very popular among the life-hacking crowd, as it improves your health while simplifying your life at the same time.

Who Should Be Careful Or Avoid It?

Intermittent fasting is certainly not for everyone.

If you’re underweight or have a history of eating disorders, you should not fast without consulting with a health professional first.

In these cases, it can be downright harmful.

Should Women Fast?

There is some evidence that intermittent fasting may not be as beneficial for women as it is for men.

For example, one study showed that it improved insulin sensitivity in men, but worsened blood sugar control in women (33Trusted Source).

Though human studies on this topic are unavailable, studies in rats have found that intermittent fasting can make female rats emaciated, masculinized, infertile and cause them to miss cycles (34Trusted Source, 35Trusted Source).

There are a number of anecdotal reports of women whose menstrual period stopped when they started doing IF and went back to normal when they resumed their previous eating pattern.

For these reasons, women should be careful with intermittent fasting.

They should follow separate guidelines, like easing into the practice and stopping immediately if they have any problems like amenorrhea (absence of menstruation).

If you have issues with fertility and/or are trying to conceive, consider holding off on intermittent fasting for now. This eating pattern is likely also a bad idea if you’re pregnant or breastfeeding.

Safety and Side Effects

Hunger is the main side effect of intermittent fasting.

You may also feel weak and your brain may not perform as well as you’re used to.

This may only be temporary, as it can take some time for your body to adapt to the new meal schedule.

If you have a medical condition, you should consult with your doctor before trying intermittent fasting.

This is particularly important if you:

Have diabetes.

Have problems with blood sugar regulation.

Have low blood pressure.

Take medications.

Are underweight.

Have a history of eating disorders.

Are a woman who is trying to conceive.

Are a woman with a history of amenorrhea.

Are pregnant or breastfeeding.

All that being said, intermittent fasting has an outstanding safety profile. There is nothing dangerous about not eating for a while if you’re healthy and well-nourished overall.

Migraine Headache – Symptoms and Treatment

14 Foods to Eat on a Ketogenic Diet 2021