Ventilatory response to exercise lowered among patients with obesity
As a patient’s magnitude of obesity increased, the ventilatory response to exercise decreased, researchers reported in the Annals of the American Thoracic Society.
“Because obesity is a major public health concern and exercise is a major component of weight loss and maintenance programs, such information on the exercise ventilatory response could have a significant public health outcome by allowing for a better understanding of the factors that may impact exercise intolerance in adults with various amounts of obesity (eg, gas exchange efficiency, dyspnea on exertion and the oxygen cost of breathing),” Bryce N. Balmain, PhD, postdoctoral research fellow at the Institute for Exercise and Environmental Medicine at Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, and colleagues wrote.
Researchers evaluated 533 patients from a surgical weight-loss center for pre-bariatric surgery testing, and all patients performed an incremental maximal cycling test. Patients were categorized based on BMI categories of 30 kg/m2 to 39.9 kg/m2 (n = 150), 40 kg/m2 to 49.9 kg/m2 (n = 253) and at least 50 kg/m2 (n = 130), and examined in groups by sex and age (younger than 50 years and 50 years or older).
The primary outcomes were differences in minute ventilation and carbon dioxide elimination slope between each BMI category, age and sex.
There were no significant interactions between BMI category, sex and age in the cohort (P = .75). Minute ventilation and carbon dioxide elimination slope decreased as a patient’s BMI increased, with 29.1 for those with a BMI of 30 kg/m2 to 39.9 kg/m2, 28.4 for those with a BMI of 40 kg/m2 to 49.9 kg/m2 and 27.1 for those with a BMI of at least 50 kg/m2. In addition, this slope was elevated in women compared with men (28.9 vs. 26.7; P < .05).
Researchers observed no age-related differences between BMI categories (P = .55).
There was an elevation in partial pressure for end-tidal carbon dioxide at the ventilatory threshold among those with a BMI of at least 50 kg/m2 compared with those with a BMI of 30 kg/m2 to 39.9 kg/m2 and 40 kg/m2 to 49.9 kg/m2 (P < .01).
“These findings have important clinical implications and suggest that obesity presents a unique challenge to augmenting exercise ventilation, such that the increase in the ventilatory response to exercise becomes blunted as the magnitude of obesity increases,” the researchers wrote.