For Muslims, observing intermittent fasting is one of the core pillars of worship Allah has mandated upon us.

“O you who have believed, decreed upon you is fasting as it was decreed upon those before you that you may become righteous.” [Surah Baqarah; 183]

The Days of Dhul-Hijjah

As the blessed days of Dhul Hijjah are upon us, many Muslims around the world are honoring these days by observing fasting once again, as it is narrated by Ibn `Abbas: The Prophet said, “No good deeds done on other days are superior to those done on these (first ten days of Dhul Hijja).” Then some companions of the Prophet (ﷺ) said, “Not even Jihad?” He replied, “Not even Jihad, except that of a man who does it by putting himself and his property in danger (for Allah’s sake) and does not return with any of those things.” [Sahih al-Bukhari 969]

Especially rewarded is the fast of the 9th of Dhul Hijjah, the day of Arafat, as narrated by Abu Qatadah: The Prophet said, “Fast the Day of Arafah, for indeed I anticipate that Allah will forgive (the sins) of the year after it, and the year before it.” [Jami` at-Tirmidhi 749]

The Prophetic Tradition of Restraint

As a young child, I remember doing a “half roza” (a half a day of fasting) in Ramadan and feeling so happy that I was able to make it from before sunrise to, well, about noon without eating, and then enjoying a nice lunch that my mom had prepared for me. I remember the feeling of accomplishment and also the anticipation knowing that years from now I too would join the grown-ups in fasting full days for the whole month. In between those two milestones was a community break fast party at our home where I was celebrated for completing my first full fast from before sunrise to sunset.

Why, as a child, was I practicing what sounds like such a difficult feat? Not because I had researched the health benefits of fasting, or because it was inherently enjoyable to deprive myself of my favorite treats during daylight hours; it was that because even as a child, I understood that this was a deed ordained by Allah , that this was a deed beloved to Allah , and that what my Lord prescribes for me is good for me. Also – as stated in the above mentioned ayah from Surah Baqarah – , the purpose of fasting is to attain taqwa.

During the time of the Prophet , outside of Ramadan, food was not consumed without restraint. The Prophet fasted Mondays and Thursdays as well as the three white days of every month.

It was narrated from Abu Hurairah that the Prophet used to fast on Mondays and Thursdays. It was said: “O Messenger of Allah, why do you fast on Mondays and Thursdays?” He said: “On Mondays and Thursdays Allah forgives every Muslim except two who have forsaken one another. He says: ‘Leave these two until they reconcile.’” [Sunan Ibn Majah 1740]

In another narration by Qatadah Ibn Malhan al-Qaysi: The Messenger of Allah used to command us to fast the days of the white (nights): thirteenth, fourteenth and fifteenth of the month. He said: “This is like keeping perpetual fast.” [Sunan Abi Dawud 2449]

On a day to day basis, most of the time food was consumed once or twice a day. There was not a schedule of three meals a day with snacks in between. There is the well-known hadith about not eating to one’s full but rather leaving ⅓ for air and ⅓ for water and only ⅓ for food.

Miqdam bin Madikarib said: “I heard the Messenger of Allah say: ‘A human being fills no worse vessel than his stomach. It is sufficient for a human being to eat a few mouthfuls to keep his spine straight. But if he must (fill it), then one third of food, one third for drink and one third for air.’” [Sunan Ibn Majah 3349]

And, on the days that the Prophet did not find anything to eat in the house, he fasted, and continued to perform his duties to his family and the community in this state. What we learn from this is that the body can go long periods of time without eating.

As an adult, and as an endocrinologist who understands the many health benefits of fasting, my primary purpose for fasting has not changed. However, I appreciate that aspect of fasting as well.

Nowadays, fasting has become popular in the mainstream health-conscious community and has been termed ‘intermittent fasting.’ This includes delineating certain hours for fasting with a smaller window for eating. This could be something like 14:10, or 16:8 (16 hours of fasting and an 8 hour window of eating). In a world where food is plentiful for many, often the only hours one is not eating is during sleeping hours. In this case, getting used to even fasting for 12 hours can be a beneficial starting point.

The Physical Benefits of Intermittent Fasting

How does intermittent fasting benefit our bodies? What is the purpose of going hours without eating?

Among the benefits of fasting the body as described by Mark Mattson, a neuroscientist at Johns  Hopkins who has studied IF for many years:

• The body goes from burning sugar for energy to burning fat. He coined this term, ‘metabolic switching.’ In order to reach this state, the body has to first use up the calories consumed by the last meal, before it starts burning one’s fat for fuel. This of course leads to weight loss, which is one of the most obvious benefits.

Other benefits include¹Fung, Jason. The complete guide to fasting: heal your body through intermittent, alternate-day, and extended fasting.Victory Belt Publishing, 2016.:

• Improves mental clarity and concentration
• Lowers blood sugar levels
• Improves insulin sensitivity
• Increases energy
• Lowers blood cholesterol
• Prevents Alzheimer’s disease
• Extends life
• Reverses the aging process
• Decreases inflammation

These benefits are related to keeping insulin levels in a steady low state without peaks and troughs. Insulin is a fat-storing hormone, and is released in response to the consumption of sugar. Every time one eats sugar (and other carbohydrates like rice that are quickly converted to sugar), there is a sharp rise in insulin levels signaling the body to store fat, and then a fall in levels over time. We know that cells cannot store fat and burn fat at the same time, so, if one is constantly eating, there is no opportunity for the insulin level to come down and stay at a low level. Most of the body’s fat-burning starts at six hours and increases exponentially after 12 hours.

One study was conducted on participants who ate for 14 hours or more and were already overweight. They were instructed to decrease that to a ten-hour window to eat all their meals and beverages without any restrictions, including caloric. All of the participants lost an average of four percent of their total weight in just four months.

For this reason, many people around the world have adopted fasting as ‘intermittent fasting’ or ‘time-restricted eating.’ For people who are used to fasting Ramadan, and the other recommended days of fasting, and would like to continue the benefits on other days, here are some simple steps one can take to get one’s body used to it.

1. If you’re not hungry, don’t eat. Becoming mindful and aware of one’s states and hunger signals helps to eat only when one is hungry.
2. Try to eat one’s last meal early and don’t snack afterwards.
3. Try to start out with at least a 12 hour window of fasting, and increase the time duration as able.

For some people with certain hormonal imbalances, fasting for too long may be detrimental. One should always consult with their own personal physician to determine what is best for them.

The Spiritual Benefits of Intermittent Fasting

Just like with anything in life, the physical is always attached to the spiritual, and this is no different for fasting. As we saw earlier in the ayah about fasting, its purpose for us as Muslims is to help us to attain a higher state of God-consciousness. The ego is fed with food and drink, and limiting these helps to subdue one’s ego. It is the ego that creates barriers between us and closeness to Allah .

As a day of fasting progresses and the blood sugar level goes lower and lower, one’s body starts to feel weaker and weaker; but one often feels more of a sense of peace as this happens. As an activity, try and become aware of your states throughout a day of fasting. At that weakest moment, right before it is time to break the fast, how do you feel? Calm? Clear-headed? I joke with my students that at that point of the lowest blood sugar, one does not even have the energy to argue, overthink, or have any internal objection to anything. It is indeed a powerful state to be in, and often supports one to be in a state of submission to Allah .

In conclusion, intermittent fasting is a blessing in that it is a rewarded obligation, and yet has so many additional benefits that we know of, and so many that we do not yet know of. Ramadan is a good training time for fasting, but think about how you can incorporate it into your life outside of Ramadan. The Dhul Hijjah fasts are a great place to start! However, always be sure to discuss with your doctor before undertaking intermittent fasting or any other health program.

Related reading:

– The Psychological Benefits of Fasting (Saum)

The Psychological Benefits of Fasting (Saum)