Being obese can increase the risk for numerous health problems. Being underweight isn't healthy either; it may even raise the risk for chronic lung disease.
"Work with a dietitian to establish a diet for maintaining a healthy weight."
This research was led by Gundula Behrens, PhD, of the Department of Epidemiology and Preventive Medicine at Regensburg University Medical Center in Germany.
The researchers used data from 113,279 participants in the National Institute of Health-AARP Diet and Health Study. All participants were 50 to 70 years of age when the study started in 1995-1996, and none had a diagnosis of COPD, heart disease or cancer at the time.
COPD is a group of progressive lung diseases, such as bronchitis, that block airflow and make it hard to breathe. COPD is caused by inhaled toxic particles from cigarettes, air pollution or occupational dust.
Participants in this study filled out questionnaires about their physical activity, smoking, incidence of COPD and information about their body size and proportions during follow-up.
A decade after the start of the study, 3,648 people had been diagnosed with COPD.
Dr. Behrens and team found that COPD was more common among the severely obese (body mass index of 35 or more) and the underweight (body mass index lower than 18.5). However, after adjusting for waist size, being underweight was associated with an increased risk for COPD, but being overweight was not.
A waist circumference equal to or greater than 110 centimeters (about 43 inches) in women or 118 centimeters (about 46 inches) in men was associated with a 72 percent greater risk for COPD, the researchers found.
Being underweight increased COPD risk by 56 percent.
Compared to never being active, being physically active five times a week was associated with a 29 percent lower risk for COPD.
The researchers also found that having a large hip circumference reduced the risk of developing COPD by 29 percent.
Dr. Behrens and colleagues suggested that exercise reduces the risk for COPD because it decreases inflammation, whereas overall and abdominal body fat increase the risk for COPD because they increase inflammation.
These authors also hypothesized that underweight people had higher rates of COPD because of malnutrition and reduced muscle mass, which makes them more susceptible to the disease in the first place.
"Our findings suggest that next to smoking cessation and the prevention of smoking initiation, meeting guidelines for body weight, body shape and physical activity level may represent important individual and public health opportunities to decrease the risk of COPD," the authors concluded.
This study was published online in CMAJ (Canadian Medical Association Journal) on July 7.
The research was supported in part by the Intramural Research Program of the Division of Cancer Epidemiology and Genetics at the Nation Cancer Institute. The authors declared no conflicts of interest.