Researcher Lesley Campbell said sedentary lifestyle rather than overeating was to blame for the country's ballooning problem.

``Australia prides itself on its athletes and the Olympics -- well, we've got a small band of superathletes but that competitive stuff discourages activity,'' she said.

Campbell, president of the Australasian Society for the Study of Obesity, said on the eve of its scientific meeting in Brisbane the proportion of overweight men and women had increased 30 per cent in six years.

In 1989, 40 per cent of Australian adults were overweight or obese and by 1995 it was 55.2 per cent.

``There is no evidence that this is levelling off, it's still going upwards,'' said the professor.

``We now equal the rates in the USA where obesity is a leading cause of preventable death.''

Research atthe Garvan Institute, where Campbell is director of the diabetes centre, backed the growing concern that lack of exercise rather than food is the culprit.

``Fat doesn't seem as important as the fact that we are incredibly sedentary,'' she said.

``Studies show that one-third of Australians are totally inactive: doing nothing except getting up in the morning and taking a big breath and that's it for the rest of the day.''

Campbell said Australians spent too much time in front of a computer without moving, drove rather than walked, and ate processed meals and takeaways rather than home-cooked food.

She said a ``gym-crazed'' society saw obesity as a cosmetic issue rather than a health one, although excess body weight increased the risk of cardiovascular disease, hypertension, diabetes, cancer, and arthritis.

The focus should be on increasing the level of activity every day, such as taking the stairs instead of the lift, and getting out of your armchair to change TV channels.

Even a small reduction inbody weight could have a big health benefit, she said. ``A 10 per cent reduction in body weight corresponds to a 20 per cent reduction in heart disease and favourable changes in cholesterol, blood pressure, blood glucose and other risk factors.''

The Australian Bureau of Statistics said last week 53 per cent of men and 43 per cent of women played sport of some sort or other.

Women preferred aerobics while men liked a round of golf.