When fats are the respiratory substrate, the value of RQ would be
Approx. 0.7
When fats are the respiratory substrates, they are hydrolysed to glycerol and fatty acids. The complete oxidation of glycerol yields an RQ of approx. 0.86. As fatty acids are deficient in O2, they require more O2 for oxidation as compared to CO2. Therefore, O2 absorption is more and CO2 liberation is less, and the RQ becomes less than 1.