What is the typical value for the normal respiratory quotient?

What is the typical value for the normal respiratory quotient?

• A. 0.8
• B. 0.9
• C. 1.0
• D. 0.7

Answer: (A)

The respiratory quotient (RQ) is the ratio of CO2 produced to O2 consumed during metabolism. It reflects which fuels the body is burning. For a typical mixed diet, the RQ sits around 0.8 because fat and carbohydrate oxidation together yield about this ratio, with protein contributing in a similar range. Carbohydrate alone gives about 1.0, fat alone about 0.7, so 0.8 best represents normal mixed-substrate metabolism. The other values correspond to more extreme fuel sources, not the usual resting mix.

The respiratory quotient (RQ) is the ratio of CO2 produced to O2 consumed during metabolism. It reflects which fuels the body is burning. For a typical mixed diet, the RQ sits around 0.8 because fat and carbohydrate oxidation together yield about this ratio, with protein contributing in a similar range. Carbohydrate alone gives about 1.0, fat alone about 0.7, so 0.8 best represents normal mixed-substrate metabolism. The other values correspond to more extreme fuel sources, not the usual resting mix.