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."
CHEST is a peer-reviewed journal published by the ACCP.
It is available online each month at http://www.chestjournal.org
. ACCP represents more than 15,700 members who provide clinical respiratory,
critical care, and cardiothoracic patient care in the United States and throughout
the world. ACCP's mission is to promote the prevention and treatment of diseases
of the chest through leadership, education, research, and communication.
Weight Loss Forum
Source: American
College of Chest Physicians
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