Intermittent fasting is one of the most studied dietary interventions in modern nutrition science. Research links it to reduced inflammation, improved metabolic health, better cognitive function, and increased longevity markers. The Prophet fasted twice a week and had done so for years before any of this was discovered.
He fasted on Mondays and Thursdays. When asked why, he gave an answer that goes far beyond nutrition.
Why Mondays and Thursdays
The Prophet was asked about fasting on Monday. He said: “That is the day on which I was born, and the day on which I received revelation.” (Muslim 1162). For him, Monday carried personal spiritual significance. He marked it with gratitude expressed through worship.
He also said: “Deeds are presented to Allah on Monday and Thursday. I love for my deeds to be presented while I am fasting.” (Tirmidhi 747, graded hasan). Twice a week, the record of what you have done is raised. Fasting on those days is a way of meeting that presentation in a state of worship.
What the research confirms
Two fasting days per week, with normal eating on the others, is now one of the most studied intermittent fasting protocols. Studies consistently show reductions in inflammation markers, improved insulin sensitivity, reduced visceral fat, and cognitive benefits including improved focus and memory consolidation. The effect on longevity markers is among the most promising areas in current nutrition research.
The Prophet also fasted the 13th, 14th, and 15th of each Islamic month, known as the White Days. Three days each lunar month, two days each week. A pattern of regular, non-extreme food restriction that modern nutrition is now recommending as one of the most sustainable approaches to metabolic health.
The spiritual dimension science cannot measure
The health benefits are real. But they are not why the Prophet fasted. He fasted because he loved for his deeds to be presented to Allah while he was in a state of worship. He fasted Monday in gratitude for the day of his birth. He fasted because hunger is a teacher, and a full stomach is sometimes the enemy of taqwa.
Fasting teaches the nafs that it is not in charge. When hunger arrives and you do not act on it, you establish that your desires do not rule you. That discipline, practised twice a week across years, quietly reshapes the character. The Prophet described the fasting person as having two moments of joy: the joy at breaking the fast, and the joy of meeting Allah. (Bukhari 1904). Two acts of worship framing one day.
How to start
- Begin with one day. Monday or Thursday, whichever fits your week better. A standard fast from Fajr to Maghrib, with no food or drink during daylight hours.
- Set the intention the night before. The Prophet said intention before Fajr is required for voluntary fasts. A brief niyyah before sleeping: “I intend to fast tomorrow, Monday, for the sake of Allah.”
- Break it simply. Dates and water at Maghrib, as the Prophet did, before a modest meal. The fast is not an excuse for a large iftar.
- Build to both days gradually. One day per week for a month, then both. Sustainability matters more than ambition here.
Frequently Asked Questions
Why did the Prophet fast on Mondays and Thursdays?
He gave two reasons: Monday was the day of his birth and the day revelation first came to him, so he honoured it with gratitude through fasting (Muslim 1162). And both Monday and Thursday are the days when deeds are presented to Allah, so he loved his deeds to be presented while he was fasting (Tirmidhi 747).
What are the health benefits of fasting twice a week?
Research on twice-weekly fasting protocols shows reductions in inflammatory markers, improved insulin sensitivity, reduced visceral fat, and cognitive benefits including improved memory consolidation and focus. These benefits begin to appear within weeks of consistent practice and accumulate over time. The Prophet’s pattern of Monday, Thursday, and the White Days represents one of the most researched intermittent fasting approaches in modern nutrition science.
Is a niyyah required for voluntary fasts?
Yes, for voluntary fasts, scholars hold that intention must be made before Fajr. Unlike Ramadan where the general intention for the month is sufficient, each voluntary fast requires its own niyyah made the night before or before dawn. The intention is in the heart, not spoken aloud, though some scholars permit verbalising it as an aid to focus.
This Monday. Make the intention tonight. One fast, for the day he was born, for the day your deeds are raised. See what it does to the week that follows it.