It's Ramadan, and Shazma Gaffoor hasn't eaten or drunk for seven hours when we speak. She still has another two hours to go until she can break her fast.
The practice of fasting from dawn to dusk is central to this Muslim holy month and its purpose is to to develop God-consciousness, or Allah's awareness ("Taqwa" in Arabic).
"It's the one thing that God asks of us. And that's why Ramadan is so special," she says. "This is actually a month of cleansing your sins."
Many of the world's religions incorporate some kind of purification ritual into their practice — whether it's baptism, bathing before prayer, or engaging in sweat lodges as some Indigenous Americans do.
And fasting too is common across faiths. Jews have Yom Kippur, Christians observe Lent, Hindus commonly fast on a new moon day, and Catholics traditionally don't eat meat on Fridays.
But the Ramadan fast is definitely one of the more challenging purification rituals practised in Australia today.
"It's just like a workout," says Shazma. "It's an amazing mechanism. Your body just remembers it, just goes with it.
"I feel quite full now that my stomach has shrunk. You become very comfortable and you get used to it."
As well as developing godliness, fasting also helps cultivate concern for those less fortunate than yourself.
"There are people who live like that … not knowing where they're going to have the next drink of water. That's a reminder of it, when the stomach rumbles," she says.
"There's the control. We can walk to the fridge and grab a drink but we choose not to. Many don't have that choice."
Why fasting is tied to purity and morality
So what has fasting got to do with being pure — or "tahir" in Arabic?
"Fasting purifies the physical body from toxins, helps discipline the soul and purify it from the blameworthy," says Professor Mohamad Abdalla.
He's the director of the Centre for Islamic Thought and Education at the University of South Australia.
"Morality is directly related to good and bad actions and behaviours," he says.
"Purity is related, in that Islam requires from its adherents to cleanse their hearts and actions from any indecent, immoral and evil act or behaviour."
So, purification involves a lot more than just fasting. During Ramadan one must also refrain from sex during daylight hours, as well as any obscenity, vulgarity, arguments or fighting.
And purification isn't restricted to the month of Ramadan, it's integral to the daily rituals of Islam.
"For the ritual prayers, it means to perform ablutions … washing of the hands, mouth, face, hands, and feet with clean water (without being wasteful)," Professor Abdalla says.
"Islam also requires a purificatory bath after intercourse."
How and why did purification rituals evolve?
Many of these purification rituals make absolute sense from a health perspective, but how did they become absorbed into religious practice?
Jonathan Goodman is a doctoral student in human evolutionary studies at the University of Cambridge, with an expertise in cultural practices with evolutionary consequences.
"Generally speaking, we'd expect cultural selection to take place on those practices that tend to benefit, on average, all individuals in a given group," he says.
"So insofar as rituals led to health benefits, we'd expect them to be selected for. That doesn't mean that health benefits aren't incidental consequences of ritualistic practices."
One example that Goodman offers is the mikvah in Judaism, where individuals bathe in a pool to achieve purity.
"This probably emerged because of the benefits generally associated with bathing in clean water, but that's just an assumption given the logic of cultural evolutionary theory."
But he notes that many purification practices can be just as much about social control as they can be about cleanliness.
Goodman believes that a greater understanding of the links between some rituals and their health benefits is important.
"Awareness of these parallels is an important tool for helping people understand that science doesn't have to collide with ritual, and really, that science and ritual are inextricably connected."
Not just a physical cleansing
But purification isn't just about physical cleansing, it's a spiritual purge as well, and as Professor Abdalla explains, both are critical to Islam.
"Spiritual purity means to have a heart that is cleansed from polytheism, envy, hatred, malice and other lowly attributes."
"The purification of the heart is a life-long process that is undertaken through deliberate and focused spiritual training otherwise known as tasawwaf or Sufism."
For Shazma Gaffoor, "it centres around gratitude".
"By doing the ritual, by praying in front of God, it's almost like a cry of help and gratitude at the same time."
"You can have a good day, you can have a bad day, just like anyone else. But it's about always trying to be better than who you were yesterday.
"Once your heart is spiritually cleansed, then everything else just sort of follows suit. And it's easier to give, it's easier to be nicer, it's easier to do the right thing."
Sweetening the deal is the big celebration at the end of Ramadan, when it's not uncommon for people to visit many homes on the one day to enjoy several banquets.
"Sometimes it's like six invites. Breakfasts at your mum's, brunch at a friend's, lunch, and then tea. So you're basically filling your stomach for the feast. It gets a bit overwhelming."
But the thing that Shazma most looks forward to at the end of Ramadan is not the food.
"I would say it's my coffee. I'm looking forward to having a coffee in the morning. That's the first thing."