With Ramadan overlapping the Olympics in 2012, this is the very question some 3,500 Muslim athletes participating in the Olympic Games this year are faced with.
In some interpretations, athletes could be excepted from fasting on the grounds that they are travellers (i.e. not in their home countries), and can make up for the days they’ve missed when the Olympics are over.
Fawaz A Gerges, director of the Middle East Centre at the London School of Economics, says: "Athletes will find Islamic preachers and scholars who will provide them with legitimate ways and means to participate in the Olympics and make up for breaking the fast by doing charity work, such as feeding poor families or fasting later.
"On balance, Islamic scholars are flexible and dynamic when it comes to questions of sports and work, and Islam is not set in stone. My instinct tells me that Islamic scholars will err on the side of flexibility in sanctioning participation in the Olympics.”
However, the scholar Sheik Fawzi Zefzaf at Egypt's leading religious institution for Sunni Muslims, Al-Azhar, says Muslim athletes are compelled to fast. "The words in Islam are clear. The Olympics are not a necessary reason to break one's fast," he says - and adds that competing athletes would not be considered to be travelling once they are in London.
Mo Sbihi, who was selected for the British Olympic 2012 rowing squad, has a different view. "Scripture says you must fast unless you have 'due cause'. The way I see it, I have a cause, which is the Olympic Games," he told the Daily Mail.
Sbihi cites the example of Moroccan Muslim goalkeeper Badou Zaki, who never fasted throughout his time at Real Mallorca in Spain’s La Liga, according to the Daily Mail. Rather than fasting, Zaki would pay for thousands of meals for the poor each year in his home country, Morocco. So this summer, Moe will be donating approximately $3,000 through charities and his family to help children in Morocco and to feed the poor.
According to a study in the British Journal of Sports Medicine conducted in 2007, which looked at two Algerian professional soccer teams, fasting during Ramadan affected players' performance significantly. The researchers noticed a decline in player’s speed, agility, dribbling speed and endurance.
Close to 70 per cent of the players in the study said training and performance were adversely affected.
Another study published in the BJSM in 2010 concluded that “Ramadan fasting had an adverse effect on performance, albeit small in magnitude, during 60 minutes of endurance treadmill running” by moderately trained Muslim men.
But not enough research has been done on the effect of fasting on athletes. In 2009, the International Olympic Committee's (IOC) nutrition working group, chaired by Ronald Maughan, a sports scientist from Britain's Loughborough University, convened to review potential problems. They came to the conclusion that fasting during Ramadan could be problematic for some athletes in some sports, but the overall impact was unknown.
"Some individual Muslim athletes say they perform better during Ramadan even if they are fasting because they're more intensely focused and because it's a very spiritual time for them," Maughan said, noting that observing Ramadan involves mental and spiritual discipline, the effects of which should not be underestimated.
There will be special provisions for fasting athletes in the Olympic Village, such as pre-dawn breakfasts, and competition venues will be providing meals immediately after sunset.
Some experts have wondered whether re-scheduling some events might be a solution. But changing timetables to accommodate Ramadan would be extremely difficult – it has implications on peak television viewing times, which is a vital factor in scheduling events.
To fast or not to fast? The debate continues...