HomeHealth articlesintermittent fastingIntermittent Fasting - Benefits | Risk Factors

This article comprises information about intermittent fasting: its functions, types, benefits, and risks.

Written by

Dr. Zeba Jabeen

Medically reviewed by

Sumiya Sulthana

Published At April 27, 2022
Reviewed AtDecember 20, 2022

What Is Intermittent Fasting?

With the increase in awareness about health and healthy eating habits, intermittent fasting has become a fad these days. Every other person in our vicinity is trying to cut down on calories and so they are adopting the ongoing trends readily. Intermittent fasting means not eating anything for a specific period of time during a day, or for some days in a week. There are cycles of fasting and eating, which provide a myriad of benefits to health.

How Does Intermittent Fasting Work?

The main aim of intermittent fasting is to burn body fat. This happens only when the calories obtained from the last meal get depleted, and the body utilizes fat stores to generate energy for its functions. This way, the fat stores in the body get deployed and fat accumulation is prevented to a great extent. Whereas, in a regular diet cycle, people consume food throughout their waking hours and attain their energy only from the eaten food. The body fat remains unexploited, and fat deposition occurs in different parts of the body causing weight gain and other critical health issues in the long term. Intermittent fasting functions by extending the duration of the phase when the body has consumed all the calories of the last meal and starts utilizing its fat stores.

How to Do Intermittent Fasting?

Various schedules can be followed for practicing intermittent fasting. The overall goal is to obtain a healthy and nutritious diet without creating chances for any health risks. There is a personal predilection as to which approach to use. But, it may end up in a trial and error method so it is better to consult a physician and a dietician before going for intermittent fasting. Also, it is not favorable for everyone and some people may have problems with it. Intermittent fasting is of the following types:

  • Fasting on Alternate Days: Eating a regular diet on the first day and, then either fasting completely or taking a meal of a maximum of 500 calories on the next day. This is continued on alternate days in patterns.

  • Fasting Twice a Week (5:2 Method): It means taking a regular diet for five days and then fasting for two days a week. There should be a non-fasting day between two fasting days. This method involves keeping the maximum calories a day (500 calories) for two days a week and maintaining a healthy nutritious diet on the other five days.

  • Fasting for a Restricted Time: In this approach, two windows are created in the daily schedule, one for fasting and the other for eating. This technique can be repeated daily, or once or twice a week; as per the choice. It is further subdivided as:

  1. The 16/8 Method: In a day, the fasting window is of 16 hours, and the eating window is only 8 hours, that is eating between 10.00 AM to 6.00 PM only. This method is widely practiced as most people fast while they are asleep, and then they easily prolong the fast by skipping breakfast and having the first meal of the day at lunch. This routine is usually safe for first-timers.

  2. The 14/10 Method: This is also limited-time fasting, in which the fasting period is a bit smaller and the eating period is slightly bigger. The fasting period consists of 14 hours and the eating period is 10 hours in a day.

  • Fasting for 24 Hours: This approach includes fasting for a complete 24 hours, that is either from breakfast to breakfast or from lunch to lunch. It is only followed once or twice a week. However, this method can have severe adverse effects like headache, fatigue, irritability, etc. so it is of utmost importance to immediately return to a regular nutritious diet on non-fasting days.

What to Eat During Intermittent Fasting?

During the fasting period, water or other non-calorie beverages like black coffee or black tea can be consumed. In the eating phase, a healthy nutritious diet is to be taken; devoid of processed and packaged foods, and other calorie-rich food products. Unsaturated fats, unrefined carbohydrates, and lean protein should be eaten. Overeating should be avoided.

What are the Benefits of Intermittent Fasting?

Intermittent fasting does plenty of good to the body, besides burning fat. A study in the New England Journal of Medicine claimed that intermittent fasting results in increasing lifespan, decreasing body weight, and boosting intellectual functions. Certain health benefits of intermittent fasting are:

  • Rational and Memory Functions: Intermittent fasting enhances verbal memory in adults.

  • Cardiac Functions: It helps in maintaining normal blood pressure, heart rate and improves other values of cardiac functioning.

  • Improved Physical Activity: People practicing intermittent fasting experienced loss of fat without losing muscle mass, and better performance at physical work.

  • Better Tissue Health: It provides protection against tissue damage during surgery and a better prognosis.

  • Prevents Obesity and Other Related Diseases: Fat loss and enhanced physical activity decrease the chances of obesity, diabetes, sleep apnea, and certain cancers.

  • Decreases Inflammation: Intermittent fasting lowers inflammation throughout the body and provides relief in inflammation-related conditions like Alzheimer’s disease, arthritis, asthma, multiple sclerosis, and stroke.

Some tips can help in gaining the utmost advantages of intermittent fasting. They are as follows:

  • Sugars and refined grains should be avoided, instead, fiber-rich foods, healthy carbohydrates, and fats should be consumed.

  • Avoid snacking between meals and let the body use its fat stores.

  • Being physically involved in activities during the day.

  • Avoid eating just before bed or munching all the time.

  • Following an easy routine of fasting, usually confining the eating phase to daytime and fasting for the evening and night.

Are There Any Risks Associated With Intermittent Fasting?

Intermittent fasting is usually suitable for everyone yet, there are some exceptions. It is strictly prohibited for the following:

  • Children below 18 years of age.

  • Pregnant or lactating women.

  • People with diabetes, kidney stones, gastroesophageal reflux disease, and some chronic conditions.

  • Patients with eating disorders.

For otherwise healthy individuals, there are some adverse effects of intermittent fasting like persistent hunger, fatigue, insomnia, irritability, nausea, headache, temperature sensitivity, etc. but these effects mostly last only for a month.


Intermittent fasting is a lifestyle change and a metabolic switch with a plethora of health benefits. It affects both the body and the brain. Yet, its effects are different on different people so before taking a leap into it, a consultation with a registered physician is a must. The consultation will help in avoiding its detrimental effects and will provide the right guidance for each individual.

Frequently Asked Questions


What Is Intermittent Fasting and What Are Its Rules?

Alternating between eating and fasting is known as intermittent fasting (IF). There are a number of approaches, but the most popular ones are the 16/8, 5:2, and alternate-day fasting strategies. In 16/8 fasting, one must eat in the eight-hour period and fast in the 16-hour period in a 24-hour cycle. In the 5:2 plan, the eating period is five days, and the fasting period is two days, where only 500 calories can be consumed. One should only take non-caloric beverages like water, tea, or coffee while fasting. Whereas the person can eat whatever they like during the eating period, however maintaining a balanced and nutritious diet is advised.


Which One Is Better Fasting for 12 Hours or 16 Hours?

The 16/8 approach, which involves fasting for 16 hours and eating within an 8-hour window, is the most often-used type of intermittent fasting. Yet, studies indicate that fasting for at least 12 hours has health advantages as well, including better blood sugar regulation and weight loss.


Is It Possible to Lose 1KG a Week by Intermittent Fasting?

Intermittent fasting can aid in losing 2.20 pounds each week, but it depends on the starting weight, nutrition, and exercise regimen. To lose 2.20 pounds of weight, one must have a calorie deficit of 3,500 calories per week, which should be achieved through diet, activity, and intermittent fasting.


What Changes Can Be Observed After One Week of Intermittent Fasting?

A person will lose weight, have more energy, have better digestion, and have clearer thinking after a week of intermittent fasting. But, depending upon the individual body composition and nutrition, the outcomes may differ.


What Is a Suitable Time to Start Intermittent Fast?

According to personal preferences and schedules, different people may have different ideal times to intermittent fast. The phrase "breakfast-skipping" or "16:8" intermittent fasting came about because many people find it simpler to fast overnight and skip breakfast. This entails eating for eight hours and then fasting for the following sixteen. As an alternative, some individuals favor skipping dinner in favor of eating their meals earlier in the day. Individuals must try different plans to find the one that suits them. 


What Are the Harmful Health Effects of Intermittent Fasting?

Particularly when beginning a new fasting routine, intermittent fasting can have negative side effects like hunger, headaches, exhaustion, irritability, and problems concentrating. Once the body becomes used to the new eating habits, these symptoms usually go away in a week or two. In some situations, if not carried out appropriately, intermittent fasting can potentially aggravate pre-existing medical issues or result in nutritional shortages. It is crucial to pay attention to the body's signals and get medical help if they encounter any negative consequences.


What Are the Foods to Be Avoided During Intermittent Fasting?

While there are no specific items to stay away from when fasting intermittently, it is typically advised to limit the intake of high-calorie, high-carbohydrate, and high-fat foods during the eating window. To improve satiety, energy, and overall health, place an emphasis on nutrient-dense foods, including fruits, vegetables, lean protein, and whole grains. Also, it is crucial to hydrate by consuming lots of water, unsweetened beverages, and herbal teas.


Which One Is Better During Intermittent Fasting, Skipping the Breakfast or the Dinner?

With intermittent fasting, skipping breakfast or dinner is a personal decision, depending on schedules and preferences. But, because it fits with their circadian cycle and enables them to have a more communal dining experience, most people find it simpler to skip breakfast and eat their meals during the day. Furthermore, skipping breakfast can lessen the possibility of late-night munching, which can obstruct sleep and weight loss objectives. Some people, especially those who have an early morning routine or prefer a lighter dinner, may find it more convenient to miss dinner.


How Can a Newbie Begin Intermittent Fasting?

It is advised for beginners to begin with shorter fasting intervals and then progressively extend them. As an illustration, start with 12- to 14-hour fasts and gradually advance to 16- to 18-hour fasts. To maintain general health, it is also crucial to drink enough water and eat nutrient-dense foods throughout the eating window. To prevent undesirable effects, it is also crucial to pay attention to the body and modify the regimen as necessary.


Is Sleeping the Same as Fasting?

Certainly, as it entails refraining from eating and drinking for an extended period of time, napping can be seen as a type of fasting. The body experiences a number of physiological changes during sleeping, including an increase in growth hormone release and a drop in insulin levels, which are similar to those experienced during a fast. It is crucial to remember that there are several types of fasting, and the advantages of fasting might change based on the kind and length of the fast.


Can a Person Fast for 16 Hours Every Day?

Daily fasting for 16 hours might be a secure and efficient method to reduce body fat and enhance general health. Intermittent fasting has been linked to better insulin sensitivity, decreased inflammation, and other health advantages, according to studies. To ensure one is obtaining adequate nutrients throughout their eating window, it is crucial to pay attention to the body's signals. It is also crucial to keep in mind that not everyone can benefit from intermittent fasting, including pregnant women, people with a history of eating problems, and people with specific medical issues.


Is It Necessary to Practice Intermittent Fast Every Day?

Daily intermittent fasting can be a practical strategy for shedding pounds and enhancing general health. But, it is crucial to make sure one is getting enough calories and other necessary nutrients throughout the eating window. Also, one should be conscious of how fasting affects one's body and modify it as necessary. Before beginning any fasting routine, it is advised to speak with a healthcare provider.
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Sumiya Sulthana
Sumiya Sulthana


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