Intermittent Fasting: How to Do It and How Long Should You Do It?

Intermittent fasting involves alternating between periods of fasting and eating. Unlike a strict diet, it offers flexibility by allowing you to choose your meal times while promoting a normal diet during eating periods. Although increasingly popular today, it is not a new practice. Its roots date back thousands of years and are embedded in various cultures and religious practices around the world. 

Historically, fasting has been observed in various spiritual traditions for purposes of purification, discipline, or spiritual connection. For example, fasting has been practiced in Christianity during Lent, in Islam during the month of Ramadan, in Judaism on Yom Kippur, and is found in countless religious and spiritual traditions. Beyond its religious origins, fasting has also been mentioned in medical and philosophical contexts by historical figures such as Hippocrates, the father of modern medicine, who recommended fasting to improve health. However, the concept of modern intermittent fasting (as a method of weight and health management) has emerged in recent decades, supported by scientific studies that have highlighted its potential benefits for metabolic health, weight loss and other aspects of physical well-being.

Over time, researchers and health professionals have investigated the effects of intermittent fasting on metabolism, insulin, and fat loss, and have conducted various studies to understand its mechanisms of action and its impacts on the human body. Thus, although intermittent fasting has its roots in ancient and traditional practices, its modern adaptation as a method for weight management and health is based on a combination of scientific studies, clinical trials, and contemporary medical research.

There are several popular methods of intermittent fasting. One involves fasting during specific periods each day, for example, by limiting food intake to a 6- to 8-hour window. Another popular approach is 24-hour fasting, done once or twice a week.

16/8, 5/2, 14/10 fasts... what are the differences? Which one is most effective?

There are several methods of intermittent fasting, the most common being 16/8, 14/10, and 5/2. The 16/8 fast involves fasting for 16 hours and limiting the eating window to 8 hours, often from noon to 8 p.m. The 14/10 fast works similarly, but with a fasting period reduced to 14 hours and a wider 10-hour eating window. The 5/2 regimen, on the other hand, involves eating normally five days a week, then limiting calorie intake to about 500 to 600 calories on two non-consecutive days of the week.

Which one is most effective depends on your personal goals and lifestyle. The 16/8 is often seen as more effective for weight loss and managing energy levels, but the 5/2 may be easier for some people to stick with because it allows for greater flexibility.

Duration and frequency of fasting phases

The optimal duration of fasting periods varies from person to person. Some opt for a 16-hour fast, while others prefer shorter or longer periods. The key is to adapt this practice to your body and lifestyle.

How long can you do intermittent fasting?

Intermittent fasting has no set maximum duration. Some people incorporate it into their lifestyle on an ongoing basis, while others prefer periods of a few weeks or months, depending on their goals. However, it is advisable to tailor it to your personal needs and health status. If you’re considering intermittent fasting over a long period, it’s essential to monitor your overall well-being and consult a healthcare professional.

Studies show its potential to promote weight loss by naturally reducing calorie intake and encouraging the use of fat reserves as an energy source. It also contributes to better insulin regulation, reduces inflammation, and can improve cardiovascular health.

Intermittent fasting, diet, and weight loss

Often adopted as a weight-loss strategy, intermittent fasting helps limit calorie intake by narrowing the window during which you can eat. It also improves insulin sensitivity, which can have a positive impact on fat metabolism. However, for lasting results, it’s important to maintain a balanced diet and not to overcompensate for fasting periods by overeating.

Take your body and its needs into account

Listening to your body is essential. Some people may experience intense fatigue or hunger at first, but these side effects tend to diminish as the body adapts to fasting. However, if symptoms persist, such as muscle wasting or extreme fatigue, it is important to consult your doctor.*

To learn more, check out our feature: What are the benefits of intermittent fasting?

Intermittent fasting is based on alternating periods of fasting and eating. During the fasting period, your body draws on its energy reserves, which can promote better fat utilisation. The idea is to limit the times when you eat to give your body time to regenerate and optimise your metabolism.

How many times a week?

It depends on the method you choose. The 16/8 or 14/10 methods are often practiced daily or several days a week. The 5/2 method is limited to two days a week. It’s possible to practice intermittent fasting every day if it fits your lifestyle, but some people find it more comfortable to do it only a few days a week for greater flexibility.

Yes, it is not only possible but also recommended to drink during the fasting period to stay hydrated. Water, tea, unsweetened herbal teas, and black coffee are allowed, as they contain no calories and do not interrupt the fasting process. However, it is best to avoid sugary drinks or those containing sweeteners, which can stimulate insulin production and break the fast.

On fasting days, it is crucial to stay hydrated and consume nutritious foods during eating periods.

What can you eat and drink during intermittent fasting?

During the eating window, it’s important to prioritise nutrient-rich foods to avoid deficiencies. Opt for lean proteins, plant-based proteins, healthy fats (such as avocados, nuts, and olive oil), as well as nuts, vegetables, and fruits. These are excellent choices to ensure an adequate intake of essential nutrients.

During the fasting period, the only beverages allowed are those that contain no calories, such as water, black coffee, and unsweetened herbal teas. It’s important to note that consuming sugary or high-calorie beverages, even in small amounts, can break the fast and disrupt the metabolic benefits of intermittent fasting.

Intermittent fasting is not recommended for everyone. People with pre-existing medical conditions, particularly those with type 1 diabetes, should consult a healthcare professional before starting this regimen. Additionally, it is crucial to remain vigilant for signs of bad breath, which often results from the production of metabolic waste during fasting.

Combining intermittent fasting with regular physical activity can potentially enhance its beneficial effects, particularly by promoting the secretion of growth hormones. Additionally, it is important to ensure an adequate calorie intake and the quality of the foods consumed during eating periods to avoid overly rapid absorption or simple carbohydrates.

Intermittent fasting offers a new approach to managing weight and improving health, but it does require certain precautions. By adapting to your body, monitoring the signals it sends, and taking individual needs into account, this practice can be an ally in optimising overall well-being and promoting better toxin elimination, provided it is carried out in a thoughtful and balanced manner.

Coralie has spent seven years working as a journalist specialising in women’s issues. With a particular passion for beauty and well-being, she is committed to exploring natural self-care approaches. She keeps up to date with current research and trends and enjoys sharing relevant, reliable information with her readers.