What does a higher RER value suggest about the fuel being used?

A higher respiratory exchange ratio (RER) value indicates that carbohydrates are predominantly being used as fuel for energy production in the body. RER is calculated as the ratio of carbon dioxide produced to oxygen consumed during metabolism, and it reflects the types of substrates being oxidized. Typically, carbohydrates have a higher RER value (approximately 1.0) compared to fats, which have a lower value (around 0.7).

When the body’s RER approaches or exceeds the value of 1.0, it suggests that the metabolic processes are primarily relying on carbohydrate metabolism. This correlation is crucial, particularly during high-intensity exercise, where the demand for quick energy from carbohydrates outweighs the slower-release energy from fats. Thus, a higher RER value is a clear indicator of carbohydrate utilization over fat, reinforcing the understanding of fuel selection and metabolic pathways during different intensities of physical activity.