We've all heard plenty of warnings about the dangers of fast food and how it's at least partly to blame for our childhood obesity epidemic . But a new international study shows that kids who eat fast food three or more times per week are at risk for more than just a little extra weight: Those chicken nuggets  and cheeseburgers have now been linked to higher rates of asthma  and eczema  in kids.
Related: The Five Worst "Healthy" Fast Food Meals for Kids 
The study, published Monday in the medical journal Thorax , used data from more than 319,000 13- and 14-year-olds in 51 countries, along with 181,000 6- to 7-year-olds from 31 countries. All of the participants were also involved in the International Study of Asthma and Allergies in Childhood, a collaborative research project made up of nearly 2 million children from 100 countries.
WATCH: Human Guinea Pigs Paid Thousands to Eat Fast Food Every Day 
The participants' parents were asked about whether their kids experienced wheezing, rough or patchy skin, and rhinoconjunctivitis (a combination of stuffy or running nose with itchy and watery eyes) in the past 12 months. They were also asked about how frequently their kids ate certain foods, including meat, fruits, vegetables, bread, rice, nuts, milk, eggs, and commercially prepared fast food.
Learn more about the potential relation between fast food and asthma after the jump.
"We generally meant from fast food outlets as the wording was 'Fastfood/burgers'," Dr. Hywel C. Williams, a professor of Dermato-Epidemiology at the University of Nottingham in the U.K. and one of the study's authors told Yahoo! Shine. "But I guess some may have answered positively if they prepared burgers at home."
The researchers found that, out of the 15 food types in the questionnaire, only fast food showed an association with asthma and eczema in both age groups regardless of gender and socio-economic status. Three or more servings a week was linked to a 39 percent increase in severe asthma among teens and a 27 percent increased risk among younger children.
"A consistent pattern for the adolescent group was found for the relationship between symptoms and fast foods," the researchers wrote in the study. "As adolescents are generally known to be high consumers of fast food, these results that show a significant increased risk of developing each or all three conditions may be a genuine finding."
Though both eczema and asthma can be triggered by food allergies—and typical fast-food meals are filled with common allergens like gluten, dairy, egg, and soy—Williams told Yahoo! Shine that allergies probably aren't the main issue here.
"We did not look for gluten, although bread and pasta both have gluten (however gluten free pasta and bread are now widely available so when someone says yes to eating bread 3x per week it may well be that they ate gluten free as this practice is growing in some countries). So we cannot tease this out," he wrote in an email. "There is no doubt that food allergy plays an important role in some people with severe asthma and eczema, but those people tend to recognize it and avoid those foods."
"I doubt if our observation of an association between severe allergies and fast foods is mediated much by increased food allergens," he added."
A 2011 study published in Nutrition Research and Practice  suggested that additives in processed foods could also trigger an allergic reaction in some kids, but Williams and his team say that fat intake, not food allergies or additives, is probably the main culprit.
"Fast food is rich in industrially hydrogenated vegetable fats such as margarine which are dietary sources of trans fatty acids, and there is some evidence that dietary intake of trans fatty acids is associated with asthma," they wrote in their study.
Luckily, there seems to be a simple solution: Parents can combat the problem by serving more fruits and vegetables. Researchers found that three or more servings of fruits and veggies per week reduced the severity of asthma and eczema symptoms by 11 percent to 14 percent.
"Diets that have a regular consumption of fruit and vegetables are likely to protect against asthma, allergic disease and other non-communicable diseases," the researchers concluded.
— Lylah M. Alphonse
Copyright © 2012 Yahoo Inc.
Elsewhere on Shine:
America's Most Unhealthy Fast Food 
Fast Food Employees Dish About the Menu Items You Should Never Order 
13 Things Your Fast Food Worker Won't Tell You