Originally Posted by
Robert Santana
That is an academic question and impossible to answer. What is the relevance?
Your activity levels and diet will influence your substrate utilization and total daily energy expenditure. A higher VO2max is associated with measures of energy expenditure. This is because VO2 and energy expenditure are related. That is pretty straightforward. Substrate utilization not so much. If you eat a carbohydrate rich meal you will have a higher Respiratory Exchange Ratio, which indicates that you are a "better sugar burner." If you follow a keto diet you will have a lower respiratory exchange ratio, which will make you a "better fat burner." If you hyperventilate your RER will be higher as well. All things constant, if you train like an endurance athlete and follow a mixed diet your substrate utilization will be pretty balanced.