The Relationship Between Diet, Body Composition, Cardiorespiratory Fitness and Respiratory Quotient

Abstract

Background: Respiratory Quotient (RQ) indicates the oxidation of fat or carbohydrate as a fuel source for the body during energy expenditure. Resting Metabolic Rate (RMR) and RQ are often determined during the same metabolic test, yet 73% is known of what explains RMR and none is known of what explains RQ. Objective: This thesis aimed to partition the variance in RQ and explore the relationship between determinants thought to explain RQ, such as diet, body composition (fat mass (FM), skeletal muscle, and residual mass), and cardiorespiratory fitness (CRF). Design: This is a retrospective cohort design using data from the Energy Balance Study including 430 participants, healthy men and women between the ages of 21-35. Partitioning of RQ was be measured by conducting a linear regression model. Results: Only 4.8% of the variation in RQ was explained from the linear regression model including models for cardiorespiratory fitness, diet, and body composition. Of this explained variance, majority was explained by percent of total calories from carbohydrate (2.4%, P<0.01). 95.2% variance is still unknown about RQ. Conclusion: This data confirms that percent of total calories from carbohydrate is a significant contributor to RQ. Although the variables of interest in this thesis are not all encompassing, groundwork has been set for future research endeavors to determine RQ’s role in contributing information to personalized healthcare.