Intermittent Fasting: A Passing Trend or a Genuine Solution for Health?

Healthy eating
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As announced in our article on the 'in' nutrition resolutions of 2019, you've likely heard about several emerging diets, including intermittent fasting. However, this practice is not new. For example, during Ramadan, Muslims have been refraining from consuming food or drink from sunrise to sunset for centuries. So, where does this newfound fascination with fasting stem from?

Before diving into the topic, it's important to know that fasting is not advised for children and teenagers in growth, pregnant or breastfeeding women, elderly individuals, or those with liver or kidney failure.

Understanding Intermittent Fasting

Intermittent fasting involves alternating fasting periods, ranging from a few hours to more than a day, with unrestricted eating periods. For instance, a fast lasting 16 to 20 hours leaves 4 to 8 hours to consume one to two meals and possibly snacks.

Does Fasting Actually Help with Weight Loss?

Yes, like most other diets involving caloric restriction. However, intermittent fasting may be easier for some since it doesn't involve constant deprivation. Moreover, weight loss is more attributable to a decrease in body fat, meaning muscles would be better preserved. Nonetheless, additional studies are necessary to confirm this phenomenon, and maintaining long-term weight loss is not guaranteed.

Can Fasting Help Prevent or Combat Certain Diseases?

It's well-established that a 5 to 10% weight loss in obese or overweight individuals has health benefits, including improved blood sugar, blood pressure, and blood cholesterol levels. Using a low-energy diet or fasting as a weight-loss method seems to yield similar results, except for certain blood parameters that would improve more with certain fasting frequencies. However, it's crucial to manage medication properly, especially in cases of diabetes. Monitoring blood glucose levels by a healthcare professional is essential.

For some cancers, animal studies have shown that fasting can slow the growth and spread of tumors. Cancer cells would struggle to adapt to the lack of food, particularly carbohydrates, thus they would be more sensitive to chemotherapy treatments. Conversely, healthy cells would go into 'protection' mode and better withstand treatments. This phenomenon doesn't occur in all animals, and very little data has been published on humans.

What About Side Effects?

Firstly, there are, of course, hunger symptoms. Fatigue, nausea, headaches, dizziness, and irritability are also possible. Shorter fasts would have fewer immediate side effects.

Furthermore, severe caloric restriction can lead to deficiencies with harmful long-term health consequences. Many nutrition professionals also question the potential contribution of this practice to the development of eating disorders. Relying on external rules to dictate appetite means hunger and satiety signals are not heeded.

Is This the Right Approach for Me?

Intermittent fasting can be effective for weight loss and management of certain metabolic diseases. It could prove promising in reducing chemotherapy side effects, but more research is needed. This practice, however, is not suitable for everyone and should be undertaken under the supervision of qualified personnel. If you're considering fasting, don't hesitate to contact a dietitian to support you in your journey and help you achieve your goals.

There are other less restrictive and likely more sustainable ways to lose weight and promote health. Have you heard of mindful intuitive eating? If you wish to break free from restrictions and live in harmony with your body, this approach will certainly appeal to you!


Crépeau, Catherine. (2017). Le jeûne intermittent, une nouvelle thérapie? Proté, magazine: janvier 2018. Retrieved from Extenso, Le Centre de référence sur la nutrition de l’Université de Montréal. (2017). L’effet du jeûne sur le poids, le cancer et certaines maladies chroniques (État de la question).

Registered Dietitian Nutritionist