You wouldn't guess she and her husband, Alan, 68, are 30 kilometres into their 225th consecutive marathon around Australia. During that time she anticipates they will go through 12 or 13 pairs of their Vibram Five Finger running shoes.

Currently about halfway down Western Australia, they are running 365 marathons in 365 days, aiming to finish in Melbourne on New Year's Eve.

If this wasn't extraordinary enough, they are doing it on a diet consisting solely of raw fruit and vegetables – about 3000 to 4000 calories of them a day. In the last two weeks they have been through about 500 bananas, while their daily diet includes up to 20 mandarins in a sitting, plus salads, green smoothies, melons and vegetable juice.

Some areas, she says, they struggle to find their fresh food supply. Today, for instance, they and their two support crew “are literally down to our last watermelon” which they will share between the four of them until they reach their destination in the evening and can re-stock.

They have had the odd stumble over stray sticks and she suspects they have both suffered cracked ribs in falls. They move slowly, taking up to 10 hours including meal and rest stops to complete each marathon, but never take a break. "There are no rest days – we'd be here for years."

Despite this, they are in perfect health, Janette says.

“We're pretty good. The physical side is not really so much of a challenge,” she says. “It's like getting up and going to work every day, but mentally and emotionally it can be quite challenging.”

Having people pull up alongside the pair to offer support or give donations helps to keep them going. Once, a man came up to them on his motorbike "in the middle of nowhere", she says.

"He said 'G'day, how's it going?"' He then asked whether she recognised him and told her he was her cousin, whom she had not seen for 45 years.

"He'd seen us on [TV] and thought 'that's my cousin'. Then he just said 'I'm late, so see ya' and drove off."

Mostly, though, they find the juice to keep going from their diet and desire to spread the word about healthy, conscious lifestyle choices.

The grandparents have long been endurance athletes and vegetarians. But a breast cancer diagnosis spurred them to up the ante. "I was given six months to live," Janette says.

They stopped cooking and became raw vegans, blending and juicing fruits and vegetables and "increasing the amount of nutrients".

That was 10 years ago. She says the simplicity and nutrient density of their diet means vitamins and minerals are assimilated quickly by their bodies.

"Our muscles are regenerating while we're running," she says. "We're getting younger with every step."

Maintaining health and even running marathons on such a diet is not inconceivable, says sports dietitian and lecturer at Bond University, Tara Diversi.

"It all depends on what you get your body used to," says Diversi, who herself is no stranger to pushing her body to the limit, having recently swum the English Channel. "The main thing is they're getting enough carbs."

Carbohydrates, of which they are getting plenty from fruit, are key to immunity and preventing injury, she explains. It's the preferred fuel for muscles and while scientists don't completely comprehend the mechanics of it, generally speaking, "athletes who get sick all the time aren't having enough carbs".

While she says that most people couldn't do what Janette and Alan are doing on their diet without gut problems, and she raises concern about them getting enough fat, she says, "to be honest, the proof is in the pudding".

Which is precisely Janette's point. Outlandish as they might seem, they are outliers pushing the boundaries of their bodies to see what works. "We know our bodies really well now," Janette says.

"You're never too old and you're never too young to make conscious choices in life and small changes can make a really huge difference to your own health."

And although she insists their aim is not to suggest that others do what they're doing, she hopes "it's inspiring and encouraging and motivating to thousands of people – whatever it is they get from that and however they want to use it in their own life".

You can support Janette and Alan or the charities for which they are raising awareness at runningrawaroundaustralia.com/fundraisinganddonations.html

You can find their running schedule at runningrawaroundaustralia.com/runraw2013schedule.html. They invite people to say 'hi' or join them for a leg of the run.