By Holly Lake
Ottawa Sun
June 8, 2004

Breathing becomes easier with every pound shed.

That's what a team of Ottawa researchers found in a study of 58 obese women. After a strict six-month weight reduction program, participants lost an average of 44lbs, and saw their lung function and exercise levels improve greatly.

"Patients who are obese have significantly impaired lung function. Their lungs are just not working normally," said Dr. Shawn Aaron, associate professor of medicine at the University of Ottawa. "The amount of improvement seemed to correlate with the amount of weight loss. The more weight loss, the more improved function."

Starting out, study participants had an average age of 44, weighed 254 lbs. and had an average body mass index of 43.1, while 41% suffered from asthma.

For every 10% of pre-treatment weight lost, the maximum amount of air exhaled at full lung capacity improved by 5%. The team also found the amount of air exhaled forcefully in one second improved by 4%.

Led by Aaron, the researchers have not only quantified the improvement of lung function, they've also looked at why it happens. He said when someone is obese, it's as if they've laid a 20kg block on their chest.

"They cannot expand their chest wall and their respiratory muscles are working very hard to overcome the weight that is attached to them."

When weight is lost, those muscles are able to work less hard to breathe and their lungs can expand to a greater extent.

"Our study definitely says losing weight improves lung function," Aaron said. "You get that block off your chest." While the weight loss led to an overall improvement in quality of life, researchers didn't find patients' asthma improved.

"The bottom line is that even though their lungs improved, it's not because weight loss improved their asthma," Aaron said, noting obese women are 50% more likely to report having asthma than women of normal weight. That's led researchers to hypothesize that some obese patients may be misdiagnosed with asthma simply because they're displaying asthma-like symptoms such as wheezing and shortness of breath.

"Our study suggests that might be happening," Aaron said. "We didn't have the numbers to conclude definitely. We would need larger studies."

And that that will likely be his team's next step - studying obese women with asthma to determine if the diagnosis is correct or if the symptoms are simply a result of extra weight.

Aaron's team findings appear in the June issue of CHEST, the journal of the American College of Chest Physicians.

Back to news