Some might say the obesity epidemic in the U.S. started in the 1980s, but this is met by the fact that we have seen a dramatic increase in obesity rates in the last decade. According to a study published in JAMA last year, 40 percent of all adults over the age of 20 in the U.S. are obese.

It has been known by scientists that overweight or obese people are more likely to suffer from respiratory issues, from shortness of breath to the more severe obesity hypoventilation syndrome (OHS). That adds up to about 93 million people that have difficulty breathing. The reason, however, has remained a mystery up until now.

For the first time, researchers have been able to show that fatty tissue collects in the airway walls, and especially so for the overweight and obese.

John Elliot, a senior research officer at Sir Charles Gairdner Hospital in Perth, Western Australia, and first author of this study, suggests that this collection of fatty tissue changes the airways and possibly contributes to a higher asthma risk.

"Our research team studies the structure of the airways within our lungs and how these are altered in people with respiratory disease,” Elliot explains.

The common form of human obesity is typically manifests as a weight gain of about 1–2 kg per year over a period of 15–25 years, depending on the individual. This rate of yearly weight gain is quite small when spread out over 365 days. Image by Pezibear from Pixabay

The study also uncovered that the amount of fat found to line the airways was directly proportional to the body mass index, or BMI. This increased amount of fat leads to lung inflammation.

"Being overweight or obese has already been linked to having asthma or having worse asthma symptoms,” co-author Peter Noble, an associate professor at the University of Western Australia in Perth, adds. "Researchers have suggested that the link might be explained by the direct pressure of excess weight on the lungs or by a general increase in inflammation created by excess weight. This study suggests that another mechanism is also at play."

The team acknowledges that more work needs to be done to better understand the relationship between obesity and poor respiratory health. In the meantime, individuals with asthma or the like should monitor their weight.