The scientists at the University of Auckland studied data from 319,000 teens in 51 countries and 181,000 children ages 6 and 7 in 31 countries. They found that teens who ate three or more servings per week have a 39% increased chance of developing severe asthma, while kids risk increase by 27%.
The authors say that because fast food was the only dietary category shown to have an association with these conditions, the results may suggest that such a diet may actually cause asthma attacks or eczema outbreaks.
Fast foods contain high levels of trans fatty acids, which are known to affect immune reactions and inflammation.
The researchers also found that eating at least three servings of fruits and vegetables per week had a protective effect and helped reduce the risk of developing asthma and eczema.
The study was published today in the British medical journal Thorax.