Sessions: Aussie founders Nick Crocker, left, and Ben Hartney.

Sessions: Aussie founders Nick Crocker, left, and Ben Hartney.

Australians Nick Crocker and Ben Hartney believe they've reinvented Weight Watchers for the digital age.

Their start–up, Sessions, does away with the weekly meetings and weigh–ins in favour of a completely online system that gives customers access to a human "health coach" over the phone, Skype, email and text messages 24 hours a day.

The former University of Queensland students believe the growing obesity problem in Australia and the US is driven by the fact that people feel they are too busy with work, family, social and other personal commitments to live healthily.

Sessions: The program is available one tablets, computers and smartphones.

Sessions: The program is available one tablets, computers and smartphones.

But what if you had a coach constantly available to offer reminders, support, feedback and tips?

"Things always come up – hangovers, sickness, travel, family emergencies – and so the most important part of coaching is knowing how to respond to those challenges and giving the right kind of messages to the participant to make sure they stay on track," said Crocker.

Users sign up to Sessions for a 12 week "structured lifestyle modification program" and after completing a diagnostic evaluation begin with two exercise sessions a week before gradually moving up to three and then four sessions per week.

The company has been running on an invite–only basis so far but launches to the general public on Tuesday, with Australia the first market.

Sessions can also integrate devices such as Fitbit, Jawbone Up and Nike Fuelband to give an added layer of data for the coach to assess.

Crocker says 60-70 per cent of the exercise time would be found "in the margins", which could be walking to and from public transport, taking walking meetings, parking the car far from the supermarket or office or walking the dog with a neighbour.

The program also doles out homework to participants, asking them to think and write about the aspects of their life which most impact their health.

"It's about behaviour change – not just a fad diet or popular workout routine," said Crocker.

"The coach's role is to support and encourage you to get through the bad weeks and still succeed."

Crocker, who previously sold his music-discovery start-up We Are Hunted to Twitter, said Sessions had raised less than $1 million in venture capital from some of the same investors who funded Instagram and Kickstarter. He would not reveal the exact amount.

Crocker claims hundreds of people have completed the 12–week program already including a US man in his 50s who was 40 kilograms overweight and did no exercise. He slowly built up his training over the course of a year from walking to using an elliptical machine and has dropped 27 kilograms so far.

The cost ranges from $69 to $399 a month depending on the level of contact required with the health coach.

Crocker said his target market is inactive people rather than gym junkies looking for a spicier workout. The focus is on simple exercise such as walking, riding, jogging or doing gym classes.

Not long after starting in 2011, Sessions was accepted into the Rock Health start-up accelerator backed by United Healthcare, venture capital firm Kleiner Perkins and Harvard Medical School.

Crocker claims his program is being validated through a randomised clinical trial at the Mayo Clinic in the US.