Being overweight or obese does not only ruin your inner systems, but also exposes you to external factors. A new research published in the journal Inhalation Toxicology connected higher body mass index (BMI) with increased sensibility to ozone. Short-term exposure to ozone provokes a temporary lung functioning drop in many people, but now it seems that body weight biases this. Ozone forms in the upper atmosphere due to the sunlight action on oxygen.

The team at the National Institute of Environmental Health Sciences (NIEHS), the University of North Carolina (UNC) at Chapel Hill and the U.S. Environmental Protection Agency (EPA) investigated data on young (18-35 years), healthy, non-smoking male and female subjects.

"It has been known for a long time that in response to short-term exposure to ozone lung function tends to temporarily drop in many people. There has recently been interest in why some people's lung function drops more than others - age and perhaps genetics, as well as diet may play a role. We were intrigued by recent mouse studies that showed that obesity increases lung responses to ozone and wanted to see whether this applied in humans." said co-author Dr. Stephanie London, NIEHS researcher.

The data was gathered in 197 subjects exposed to ozone for 90 minutes, an interval during which they alternated 20 minutes of exercise with 10 minutes of rest. The volunteers' lung capacity was measured right before and after the exposure through spirometry (assessing the speed and volume of air exhaled from the lungs). Higher the BMI was correlated to increased ozone response.

The ozone-connected lung failure (forced expiratory volume per second or FEV1) was weakest in underweight individuals (BMI under 18.5), higher in average weight people (BMI 18.5 to 25) and highest in overweight individuals (BMI more than 25).
"It's notable that these results came out of a study that was done in a population of predominantly normal weight individuals. This suggests that these effects may be even more important in the general population where there are large proportions of overweight and obese individuals." said London, pointing to the fact that official data show that 70 % of the American adults are overweight or obese.

By now what causes this correlation is not known, but it could be all about circulatory hormones or inflammatory reaction, known to change airway hyper-responsiveness and inflammation in animal tests.

The authors warn that the research pool comprised too few obese individuals and assessed fatness based on BMI.

"Future studies of the effects of obesity on ozone response should include a targeted pool of obese and lower weight subjects, as well as measures of central adiposity such as waist circumference, given that fat deposited centrally may have a greater influence on an individual's respiratory response to ozone." wrote the researchers.