The simultaneous rise of childhood obesity and asthma has caused some experts to wonder if the conditions may be linked.
Monday's study involved about 500,000 children and teenagers in developed and non-developed countries around the globe.
While it failed to prove that fast food causes asthma and eczema, the research noted that both conditions are sometimes associated with overreactions of the immune system and that trans fatty acids could play a role in those reactions.
Eating three or more weekly servings of fruit had the opposite effect of consuming fast food, researchers found.
"What’s clear from this study as that fruits and vegetables turned up as protective factors, and fast foods turned up as risk factors," one researcher, Gabriele Nagel, told Bloomberg. "Our study provides evidence toward giving dietary recommendations in order to prevent asthma and allergies in childhood."
Nagel is affiliated with the Institute of Epidemiology and Medical Biometry at Ulm University in Germany, and was involved with the study.
Read more at Bloomberg.