WA asthma experts say children need to be doing more exercise such as swimming or competitive sport, on the back of latest research showing a strong link between childhood obesity and the respiratory condition.
They say the association could help explain the steady rise in asthma, which affects 250,000 West Australians, including one in nine children, and is the number one cause of hospital admissions in children.
The British study of almost 5000 children with asthma, published in journal PLOS Medicine, found having a higher body mass index increased the risk of asthma 55 per cent for every extra unit of BMI by age seven.
Researchers said it was possible obesity had an inflammatory effect on the respiratory system, triggering asthma symptoms.
The Asthma Foundation of WA said that though the link between obesity and conditions such as heart disease and type-2 diabetes was well known, there had been limited research into the impact of excessive weight on asthma.
Parents of children and young people with asthma needed to heed the findings of the study, which clearly showed that obesity was an important marker of asthma and could be used to prevent and manage the condition.
Foundation chief executive David Johnson said the link was not appreciated by many people, and the British study was one of the first to offer some evidence.
"It's what we have suspected but haven't been able to offer any firm proof, and it is an important message given that we don't have a cure for asthma and it might still be a long way off," he said.
It was important parents kept an eye on their children's weight and encouraged exercise, he said.
Sydney researchers revealed yesterday they had discovered a new type of lung test that could help asthmatic children better manage their condition at home.
Woolcock Institute of Medical Research said the forced oscillation technique was a big improvement on other tools because it was more sensitive and accurate.