Chest
Volume 125, Issue 6, June 2004, Pages 2046-2052
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Clinical Investigations
Pulmonary Function
Effect of Weight Reduction on Respiratory Function and Airway Reactivity in Obese Women

https://doi.org/10.1378/chest.125.6.2046Get rights and content

Background

Population-based studies have documented an association between obesity and an increased prevalence of asthma in women.

Methods

We prospectively studied 58 obese women with a body mass index of > 30 kg/m2, 24 of whom had asthma, who were enrolled in an intensive 6-month weight loss program to determine whether loss of body mass would be correlated with improvements in bronchial reactivity, lung function, and disease-specific health status.

Results

Patients lost an average of 20 kg over the 6-month period. For every 10% relative loss of weight, the FVC improved by 92 mL (p = 0.05) and the FEV1 improved by 73 mL (p = 0.04), however, bronchial reactivity did not significantly change with weight loss (p = 0.23). Patients who lost > 13% of their pretreatment weight experienced improvements in FEV1 (p = 0.01), FVC (p = 0.02), and total lung capacity (p = 0.05) compared to patients in the lowest quartile who failed to lose significant amounts of weight. Neither group experienced any significant change in methacholine responsiveness (p = 0.57). Patients who completed the 6-month weight loss program experienced improvements in respiratory health status, irrespective of weight loss.

Conclusion

We concluded that weight loss can improve lung function in obese women, however, the improvements appear to be independent of changes in airway reactivity.

Section snippets

Patients

We enrolled consecutive female subjects with a BMI > 30 kg/m2 who had entered the Ottawa Hospital Weight Loss Clinic and consented to participate in the study. We enrolled an approximately equal number of patients during the summer and winter months to try to control for potential seasonal changes in bronchial responsiveness. Patients were excluded if they had been receiving oral corticosteroids on a regular basis, if they were pregnant, if they had a history of myocardial infarction or stroke

Patient Characteristics

Fifty-eight patients were enrolled in the study, and completed baseline and 3-month assessments. Eight patients withdrew from the study before completing their 6-month follow-up assessment. The mean (± SD) age of the patients was 44 ± 13 years. Twenty-four of the 58 patients (41%) had a history of physician-diagnosed asthma (Table 1), and 21 patients (36%) were receiving medication for asthma at time of enrollment. The mean BMI of the patients entering into the study was 43.1 ± 8.8 kg/m2, and

DISCUSSION

Obesity can have a significant effect on normal lung physiology. In 1960, Naimark and Cherniak12 demonstrated that obesity is associated with reduced chest wall compliance. The reduction in chest wall compliance that is seen in obesity is reflected by a reduction in functional residual capacity, expiratory reserve volume, and vital capacity, and in patients with severe obesity, by a reduction in the TLC as well.13 The reduced chest wall compliance represents a substantial elastic load on

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This research was supported by grants from The Ontario Thoracic Society and The Asthma Society of Canada.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (e-mail: [email protected]).

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