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

## TL;DR

This study examines how obesity affects breathing efficiency during exercise in healthy adults using a large national database.

## Contribution

It investigates the association between BMI and ventilatory responses during exercise in apparently healthy individuals.

## Key findings

- Obesity is positively but negligibly associated with a higher V̇E/V̇CO2 slope during exercise.
- The association between BMI and V̇E/V̇CO2 slope is weak across the cohort.
- Adjusting for age, sex, and fitness, the effect of obesity on ventilatory responses is minimal.

## Abstract

A high minute ventilation/rate of carbon dioxide production (V̇E/V̇CO2) slope during exercise is prognostic for cardiovascular mortality among clinical populations. Obesity represents a major modifiable risk factor for cardiovascular disease. However, it is unclear whether body mass index (BMI) is associated with V̇E/V̇CO2 slope among apparently healthy adults. Therefore, we used the Fitness Registry and the Importance of Exercise National Database (FRIEND) to determine whether BMI is positively associated with V̇E/V̇CO2 slope in the context of apparently healthy adults. All participants completed a cardiopulmonary exercise test on a cycle ergometer. Linear regressions adjusted for age, sex, and race/ethnicity were used to compare the V̇E/V̇CO2 slope between adults with and without obesity (BMI </≥ 30 kg/m2). Partial correlation adjusted for age, sex, race/ethnicity, and cardiorespiratory fitness was used to determine the relation between the V̇E/V̇CO2 slope and BMI. All data are presented as median [IQR]. We set α a priori to < 0.05. The sample (n = 3534) characteristics were as follows: (1) age = 40 (17) years; (2) 20% female; (3) cardiorespiratory fitness = 27.8[10.8] mL O2●kg−1●min−1 & 2.3[0.9] L O2●min−1; and (4) BMI = 26.1[5.0] kg/m2. V̇E/V̇CO2 slope was higher in adults with obesity 25.0[3.5] compared to those without obesity 24.7[3.6] with a negligible effect size (R
2 = 0.132, adjusted R
2 = 0.131, F4,3529 = 134, p < 0.001). V̇E/V̇CO2 slope was weakly associated with BMI across the cohort (ρ = 0.079, p < 0.001). Obesity was positively, but negligibly, associated with a higher V̇E/V̇CO2 slope in the FRIEND Registry.