The number of fat West Australians has increased 25 per cent in the past decade, with one in five adults now considered obese.
New data from the 2009 Physical Activity Taskforce Adult Survey, to be released today, shows while WA adults have moderately increased their physical activity, 55 per cent weigh too much. This is up from 44 per cent in 1999.
Of particular concern to medical and public health experts is the proportion of people who are obese, which has jumped from 12 per cent to 18 per cent.
The results are in contrast to those from a survey of WA children released by the task force a few months ago, which found that while one in four was overweight or obese, the rate had not increased since 2003.
A positive finding in the adult survey was that 60 per cent of people were active enough, a small improvement in the past 10 years.
Sport and Recreation Minister Terry Waldron, who chairs the task force, said the increase in physical activity levels was positive but it was concerning that overweight and obesity was on the rise.
"Physical activity has huge benefits for health and improves physical and mental wellbeing, quality of life, social interaction and life expectancy," he said.
"But the increase in adult overweight and obesity levels is alarming and a reminder that increasing physical activity will only curb part of this problem."
Task force manager Jo Davies said increased levels of physical activity produced benefits such as preventing chronic diseases and improving mental health.
"It's encouraging that not only are more people keeping active, but they're doing it more often and for longer, and we've seen a real increase in walking and the use of cycle paths," she said.
"But the results for overweight and obesity reinforce that physical activity is only one part of the solution, and we still need to be encouraging a healthy diet."
Public Health Association president Mike Daube said while the figures showed a marginal increase in physical activity, the reality was that obesity was increasing significantly and set to get even worse.
"We are fat and getting fatter and there is no good news in sight, with obesity increasing consistently among adults and fewer adults with a healthy weight," he said.
"This is yet another alarm bell for our community, as we already know that if left unchecked the obesity epidemic will reduce life expectancy in Australia."
He repeated his call for mandatory "traffic light" food labelling so people knew what they were eating.