About half a million Muslim Australians will be participating in the month-long Ramadan fast from May 26 to June 24.
This means no fluids (including water), food, caffeine or tobacco during daylight hours.
While the benefits of intermittent fasting have been well-publicised in recent years, what happens when we fast for extended periods (as with Ramadan) and how does fasting affect those with health problems?
Ramadan poses no danger to healthy people (apart from caffeine-withdrawal headaches and the potential for dehydration if you're not careful), but it can be risky for those with existing health conditions like diabetes.
"Ramadan fasting is associated with short-term improvements in good HDL cholesterol, and reductions in bad LDL cholesterol and total cholesterol (although not in people who have diabetes)," explains dietitian Melanie McGrice. "Unsurprisingly, Ramadan has been found to lower body weight, body fat percentage and BMI (body mass index) in the short term.
"However, the long-term effects of Ramadan fasting on these risk factors remains uncertain (and unstudied). It can also be problematic for the blood glucose levels of people with diabetes."
It can also be beneficial, if managed correctly.
"Intermittent fasting can be beneficial for blood glucose levels and diabetes management," says Vania Khoury, of Diabetes NSW & ACT. "But if you're on certain medications then you need to be prepared."
Khoury says that Australian Muslims living with diabetes can put themselves at risk of serious health complications (including hyperglycaemia, hypoglycaemia and blood clots) by fasting without adequate preparation and care.
About 8 per cent of the Australian population have diabetes but rates are higher among Muslim communities.
Despite the risks, about half (43 per cent) with type 1 diabetes and most (79 per cent) of those with type 2 diabetes still fast during Ramadan.
However, many of those with diabetes who choose to fast even when advised not to (often because of family or social pressure) are reluctant to talk with their doctor.
Khoury reminds that those who are unwell, pregnant or travelling are exempt from fasting and the Koran instead suggests they participate by donating what they would normally spend on food to a charity.
Those who wish to fast can minimise their risk of health complications by planning, she says.
"The nature of the Ramadan changes in eating patterns can cause major changes in blood glucose levels considering the longer gaps between meals and the concentrated nature of the feasting," Khoury explains, recommending regular blood glucose checks.
Despite a tendency to eat in excess and eat more fatty, fried foods during the nightly feast, Khoury advises against overindulging.
"Break your fast with the traditional sunset snack of two dates, a glass of water and a bowl of soup," Khoury says. "This prophetic tradition provides an instant energy boost and helps settle your hunger. So it's meant to benefit your body and to benefit you spiritually, so eating junk food is not part of the main idea of Ramadan."
Khoury suggests sticking to the "healthy plate model" at meal times. "We usually say to people carbohydrates should fill one quarter of your plate, protein the other quarter and vegetables should fill half the plate."
She also advises those with diabetes to check in with their doctor or diabetes educator to plan each day and know when to take insulin or other diabetes medication, which may be timed according to meal times.
"Some doses may need to change" Khoury says. "Health professionals respect your commitment to your faith, but it needs to be within the context of your health."