Weight loss may help obese women breathe easier


Obese patients may be misdiagnosed with asthma

Losing weight may help obese women improve their lung function and exercise capacity but has little effect on asthma severity, a finding that may suggest obese patients can be misdiagnosed with asthma.

In a study published in the June issue of CHEST, the peer-reviewed journal of the American College of Chest Physicians, researchers found that lung function and exercise level significantly improved after obese women lost weight and that women who lost the greatest amount of weight experienced the most significant improvements. However, the same women had no significant changes in airway reactivity, a defining feature of asthma, leading researchers to believe that some obese patients may be misdiagnosed with asthma.

"Having extra weight compromises all respiratory muscles, making them work harder and less efficiently. As a result, women who are obese may limit their exercise or activity level due to shortness of breath, and, therefore, may have a more difficult time losing weight," said Shawn D. Aaron, MD, Msc, The Ottawa Hospital, Ottawa, Ontario, Canada. "As women in our study lost weight, less stress was placed on the respiratory system, which ultimately helped them breathe easier and exercise more."

Researchers from The Ottawa Hospital, the University of Ottawa, and the Ottawa Health Research Institute studied how weight reduction in obese women would affect lung function, asthma severity as measured by airway reactivity, and overall quality of life. Fifty-eight women were enrolled in a 6-month weight reduction program, consisting of a strict diet regimen, exercise, counseling, and weekly follow-up appointments. Patients had a mean age of 44 years, mean weight of 254 pounds (115 kg), and mean body mass index of 43.1, while 41 percent suffered from asthma. Patient assessments were completed prior to treatment, and 3 and 6 months after enrollment, and included a respiratory questionnaire, breathing and airway response tests, and documentation of respiratory symptoms, medication use, diet, exercise, and exposure to allergens and tobacco smoke.

Upon program completion, patients lost an average of 44 pounds (20 kg) or 17.4 percent of their pretreatment weight, and mean body mass index was reduced to 37.1. For every 10 percent of pretreatment weight lost, patients' forced expiratory vital capacity (FVC), the maximum amount of air exhaled at full lung capacity, improved by five percent. In addition, patients' forced expiratory volume (FEV1), the amount of air exhaled forcefully in one second, improved by four percent. Patients who lost more than 13 percent of their pretreatment weight had more significant improvements in lung function and exercise level than patients who lost less than 13 percent of initial body weight. Patients who lost more than 20 percent of pretreatment weight experienced the most improvement with a 10 percent increase in overall lung function. In patients with asthma, no relationship was found between weight reduction and changes in asthma severity as measured by airway reactivity, leading researchers to conclude that control of the patients' asthma did not improve with weight loss. In addition, all patients, regardless of weight loss, reported an improvement in their overall quality of life, with the most dramatic change seen in the exercise level of patients.

"Many obese patients are diagnosed with asthma due to their asthma-like symptoms of reduced lung function, wheezing, and shortness of breath, when, in actuality, their symptoms are caused by pressure on the respiratory system due to excess weight," said Dr. Aaron. "In our study, weight loss improved lung function, yet, did not affect asthma, indicating that increased lung function occurred due to stress reduction on the respiratory system, rather than improvements in asthma. It also is possible that some of our patients may have never had asthma, suggesting that other obese patients with asthma may be misdiagnosed." Researchers caution that additional studies are needed to confirm the relationship between obesity and misdiagnosis of asthma.

"Obesity has a significant impact on nearly every system in the body, leading to such conditions as cardiovascular disease, diabetes, cancer, and respiratory complications," said Richard S. Irwin, MD, FCCP, President of the American College of Chest Physicians. "Due to the extent and severity of health implications related to obesity, it is important for health-care providers, regardless of specialty, to encourage obese patients to lose weight and offer resources to support patients through the weight loss process."

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Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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