Respiratory Exchange Ratio in Obese and Non- obese Sedentary Indian Young Adults in Moderate-and Vigorous-intensity Exercise

Respiratory exchange ratio (RER) is the ratio between produced CO2 and used O2 for body metabolism. It indicates the type of fuel that is metabolized in the body. This study aimed to measure and compare the RER in non-obese and obese sedentary young adults in rest, moderate-intensity, and vigorous-intensity exercise.

This cross-sectional study was conducted with 23 non-obese and 24 obese sedentary young adults. Resting RER was measured with 12-h fasting after 15-min rest with an automated gas analyzer. Then, RER was measured during steady moderate-intensity and vigorous-intensity exercise on a cycle ergometer. RER was compared between males and females, non-obese and obese in resting, moderate-intensity, and vigorous-intensity exercise by t-test.

The Mean age of the non-obese and obese groups was 19.35±1.11 and 19.79±0.78 years, respectively. Males showed higher RER (in resting and moderate-intensity exercise) than females. In comparison to non-obese group, the obese group showed higher RER in resting (0.802±0.018 versus 0.821±0.022, P=0.001), moderate-intensity exercise (0.812±0.013 versus 0.83±0.02, P<0.001), and vigorous-intensity exercise (0.853±0.43 versus 0.914±0.032, P<0.001). Concerning resting value, RER significantly increased during moderate- and vigorous-intensity exercise in both the non-obese and obese groups.

Obese young adults use relatively more carbohydrates as fuel than non-obese in both resting conditions and during exercise. When the intensity of exercise increased, both obese and non-obese showed higher RER which indicates that sedentary young adults use relatively more carbohydrates as fuel in the higher grade of exercise.