The Health4Life program targets the common 'big six' unhealthy behaviours of young people, shown to contribute to chronic disease.

Experts in mental health, drug and alcohol prevention and nutrition have teamed together to develop a world-first online health program for Australian high school students to ensure they live well in old age.

The trial educational program, launched on Friday, targets the common "big six" unhealthy behaviours of young people, shown to be the biggest contributors to chronic disease in adulthood, such as diabetes and cancer.

These include physical inactivity, poor diet, risky alcohol use, smoking, recreational screen time and poor sleep.

Dr Katrina Champion, Research Fellow at UNSW and investigator on the Health4Life Initiative, says these six risky lifestyle factors are also implicated in short-term harms such as obesity, addiction issues, depression and anxiety.

She says the online program is about empowering students with the best knowledge and skills to secure their health into the future.

"Preventive interventions delivered in adolescence before the escalation of many risk behaviours offer an opportunity to equip young people with the capacity to make healthy decisions, increase adherence to national health guidelines and reduce the risk of later chronic disease and mental health problems," Dr Champion said.

A study of nearly 900 18-year-olds, published this month, found more than three quarters had insufficient intake of vegetables and more than half reported binge-drinking at least monthly.

Approximately one-third reported sitting for longer than recommended periods, and one quarter reported smoking.

For the trial, researchers aim to recruit 8,000 students from 80 schools across New South Wales, Western Australia and Queensland to test the online intervention program.

Participants will receive evidence-based education on the common risk factors for chronic disease, as well as life skills to help them with decision making and resisting peer pressure.

"There are some clear risks associated with drugs and alcohol, in terms of diet we want to educate them on reducing their intake of sugar, caffeine and saturated fat," Dr Champion said.

The students' health behaviour will then be tracked through a smartphone app to encourage them to put what they've learned into action.

Fruit and vegetable intake and daily steps will be monitored, as well as their mood.