A respiratory quotient (RQ) of 0.7 indicates that the substrate being respired is

The respiratory quotient (RQ) is the ratio of carbon dioxide produced to oxygen consumed (CO₂/O₂). Fats have an RQ of approximately 0.7 because they contain proportionally less oxygen and require more oxygen for complete oxidation. Carbohydrates have an RQ of 1.0, while proteins have an RQ of approximately 0.8 to 0.9.