People who are genetically predisposed to a high BMI have a higher risk of developing asthma.

“We show that people who are predisposed to being overweight develop asthma more often and have lower lung function. So it appears to be important to remain at a normal weight if you want to prevent asthma and maintain normal lung function,” says lead-author, Tea Skaaby, a senior scientist at the Center for Clinical Research and Prevention, Frederiksberg Hospital, Denmark.

In the new study, which is published in the journal Allergy, scientists used a method known as Mendel randomization. The method is named after Gregor Mendel—the father of genetics. It assumes that everyone is born with a genome that consists of random copies of genetic variants from the parents.