Many Australians risk their health by being virtually immobile for more than 70 per cent of their day, warns expert

Australians need to vacate their couches, chairs and computers in the fight against diabetes and heart disease.

Many adults can spend more than 70 per cent of their day sitting, being virtually immobile, says Professor Neville Owen of the Baker IDI Heart and Diabetes Institute.

"Physical activity is so fundamentally important and is being under-utilised in many areas of preventative health and medicine," he told AAP ahead of speaking to a Melbourne health care conference on Thursday.

While the recommended daily 30 minutes of moderate to vigorous exercise was to be commended, Prof Owen said this was only a tiny proportion of people's waking hours.

Studies had shown that sitting time was a strong predictor of health risks and resulting premature deaths, while others had shown the benefits of breaking up sitting time, especially in the workplace.

Baker IDI laboratories had done research where people sat all day then had their blood glucose, insulin and other levels measured.

"They then have one experimental day when they, very simply, just break up their sitting time every half hour, moving for two to three minutes," Prof Owen said.

This resulted in "huge improvements" in their levels.

"More activity is always better, but there is still so much more to explore, such as whether three or four longer breaks during the day could make a difference," Prof Owen said.