Obesity and Ventilatory Effciency During Exercise in the Fitness Registry and the Importance of Exercise National Database (FRIEND)

Background: A high minute ventilation/rate of carbon dioxide production (V̇E/V̇CO2) slope during exercise (i.e., ventilatory ineffciency) is more common in patients with cardiovascular disease and is prognostic of cardiovascular mortality. Interestingly, recent data in adults with obesity suggest that V̇E/V̇CO2 slopes are lower with higher body mass index (BMI) values in the context of adults with and without comorbidities. However, it is unclear whether obesity is associated with V̇E/V̇CO2 slope in adults without comorbidities. Therefore, we used the Fitness Registry and the Importance of Exercise National Database (FRIEND) to test the hypothesis that adults with obesity would have a reduced V̇E/V̇CO2 slope compared with adults without obesity in the context of no known comorbidities. Methods: We used the CDC definition for obesity as a BMI of ≥30 kg/m2. We excluded those with known chronic disease, smoking status, or any medication use. We only included adults with a respiratory exchange ratio >1.00 at peak exercise. All data are presented as median[IQR] because they failed Shapiro-Wilk normality tests ( p>0.05). For our primary analyses, we compared groups using a Mann-Whitney U test (unadjusted) and linear regression adjusted for age, sex, and race (cardiorespiratory fitness was not a significant covariate). We set α a priori to <0.05. Results: The sample (n=3588) characteristics were as follows: 1) age = 40[18] years (range 18-91 years); 2) 20% female; 3) 0.4% American Indian, 3% Asian, 14% Black, 8% Hispanic, 3% Other, 66% White, and 5% Unknown; 4) cardiorespiratory fitness = 27.8[10.8] mLO2·kg−1·min−1; and 5) 17% with obesity. As expected, BMI was different between groups (obese: 32.1[3.0], non-obese: 24.6[4.0] kg/m2, rank biserial correlation[rbc]=1.00, p<0.001). The V̇E/V̇̇CO2 slope was higher in adults with obesity (obese: 25.0[3.5], non-obese: 24.7[3.6], rbc=0.07, p=0.009). Obesity was a significant predictor of the V̇̇E/V̇̇CO2 slope (standard error of the estimate: 0.16 [95% CI 0.09-0.70], p=0.01) after covariate adjustment (model: R2=0.174, F4,3583=188, p<0.001). BMI was also related to the V̇E/V̇̇CO2 slope (ρ=0.07, p<0.001). Finally, the proportion of V̇̇E/V̇̇CO2 slope values >45 was not different between groups (obese: 0.2%, non-obese: 0.3%, X2=0.48, p=0.49). Conclusion: In contrast to our hypothesis, data from the FRIEND indicate that those with obesity exhibit mildly greater ventilatory ineffciency during exercise than those without obesity in the context of no known comorbidities. Funding: National Institutes of Health K01HL160772 (JCW), American Heart Association 23CDA1037938 (JCW). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.