Study objective: To determine the effect of obesity on pulmonary function.
Design: Case-control study, using nonobese, age- and height-matched [corrected] nonsmokers.
Setting: Metabolic and obesity clinics of two major teaching hospitals.
Patients: One hundred and three obese, lifelong nonsmokers without cardiopulmonary disease.
Controls: One hundred and ninety healthy, nonobese nonsmokers recruited from among hospital personnel.
Measurements and main results: Complete pulmonary function measurements in all patients and controls. These measurements included maximum expiratory flow-volume curve, lung volumes and airway resistance using body plethysmograph, single-breath diffusing capacity for carbon monoxide, and total lung capacity using the helium dilution technique. Obese persons were found to have lower functional residual capacity, expiratory reserve volume, and total lung capacity by helium dilution than nonobese controls. In addition, residual volume and diffusing capacity were higher in the obese group. Finally, we found that obese men, but not women, had reduced maximum expiratory flow rates at 50% and 75% of exhaled vital capacity.
Conclusion: Obesity may contribute independently of smoking habits to chronic airflow limitation in men.