Benefit of Mild to Moderate Obesity in those with COPD
Dennis Jensen, Ph.D., Assistant Professor at McGill University, presented information on the benefit of obesity on shortness of breath in those with COPD at the CHEST Annual Meeting held October 24-28, 2015, in Montreal, Quebec, Canada.
First, Dr. Jensen reviewed how obesity is defined. The most widely used method is called the BMI (body mass index) which is the ratio of weight squared to height using the metric system. Studies show that 54% of the general adult population in the United States and Canada are considered obese based on a BMI of 30 or higher.
In general, studies show that obese individuals who have COPD are less active, are hospitalized more, and require more home care compared to those with COPD and are normal weight.
However, there are a few paradoxes when other outcomes are considered. For example, obese individuals with COPD:
Dennis Jensen, Ph.D., Assistant Professor at McGill University in Montreal
Extra weight on the chest limits the lungs from over-expanding (called hyperinflation) at rest and during exercise. Hyperinflation occurs in most individuals who have COPD and is a major cause of shortness of breath.
- have a lower all cause mortality compared with those with COPD of normal weight
- can exercise to a higher level (intensity) on a stationary cycle compared with non-obese COPD individuals.
- report lower ratings of breathlessness (dyspnea) for the same level of breathing (ventilation) while exercising on the cycle than those with COPD of normal weight
When the extra weight is around the chest (called central obesity- think of an apple and not a pear), not as much hyperinflation takes place with daily activities. This makes it a little easier to breathe.
The information that Dr. Jensen presented led to an interesting discussion, particularly about what happens when someone who is overweight and has COPD loses weight. Is that good or bad for breathing? Dr. Jensen commented that there are no studies that have addressed this.
X-ray of the chest showing too much air in the lungs (hyperinflation). This pushes the diaphragm muscle down and makes it less effective.
Dr. Denis O’Donnell, another presenter at the session, commented that the benefit of obesity occurs in those with mild to moderate obesity (about 20-30 pounds of extra body weight). Extreme, or morbid, obesity causes more breathing difficulty along with other medical problems.
Dr. Denis O’Donnell, Professor of Medicine at Queen’s University, in Kingston, Ontario, Canada