Asthmatic children are 50 percent more likely to be obese in later life than their peers, new figures reveal.
Scientists believe children may be at greater risk of becoming overweight because their struggling for breath could cause them to play and exercise less.
And a side effect of many asthma medications is weight gain, scientists from the Keck School of Medicine at the University of Southern California said.
But they found using reliever inhalers when an asthma attacks hit reduce the risk of becoming obese by 43 percent.
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Having asthma and being obese may also contribute to the development of other metabolic diseases, including prediabetes and Type 2 diabetes in later life.
One in five British children aged 10 and 11 are obese while one in 11 are prescribed inhalers and other asthmatic medicines.
Lead author and postdoctoral research associate of preventative medicine Dr Zhanghua Chen said: 'Asthma and obesity often occur together in children, but it is unclear whether children with asthma are at higher risk for onset of obesity or whether obese children develop asthma, or both.
'Our findings add to the literature that early-life asthma history may lead to increased risk of childhood obesity.'
The study looked at the medical records of 2,171 five to seven year olds who were not obese when they joined the Southern California Children's Health Study (CHS).
At the start over an eighth (13.5 percent) had asthma. All the children were followed up to 10 years with an average of 6.9 years and found a sixth (15.8 percent) of all the children were obese.
The findings were confirmed using a different group of nine to ten year olds who were followed until high school graduation.
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Researchers confirmed study results in a different group of children, recruited in the 4th grade to participate in the CHS.
Senior author Professor Dr Frank Gilliland said the fact reliever but not preventer inhaler medications reduced obesity was a surprise.
He said: 'Early diagnosis and treatment of asthma may help prevent the childhood obesity epidemic
'Part of the problem may be a vicious cycle where asthma and obesity negatively affect each other.
'Our results also suggest that asthma inhalers may help prevent obesity in children.
'Although this observation warrants further study, it is interesting that the correlation exists irrespective of physical activity and other asthma medication use.'
He added, however, that overall study findings reinforce the importance of early diagnosis and treatment of asthma, which may short circuit 'the vicious cycle of asthma increasing the development of obesity and obesity causing increased asthma symptoms.'
The study was published in American Journal of Respiratory and Critical Care Medicine.