Table 8.

Respiratory quotients (RQ) for complete oxidation of energy substrates to CO₂ and H₂O in humans and other animals

Oxidation to CO2 and H2O	RQ value	Synthetic pathways	RQ value
Glucose	1.00	Glucose to fatty acid3	8.00
Glycerol	0.857	Glucose to fat2	2.05
Protein1	0.831	Protein to fat2	1.26
Fat2	0.708	Protein to fatty acid3	1.22
Fatty acid3	0.696	Glycerol to glucose	0.667
Ethanol	0.667	Protein to glucose	0.333

¹Oxidation of protein (C_4.3H₇O_1.4N_1.2) in animals is calculated as follows: Oxidation of 1.2 mole of N to 0.6 mole of urea (CH₄ON₂), C_4.3H₇O_1.4N_1.2 (protein) - C_0.6H_2.4O_0.6N_1.2 (0.6 mole of urea) = C_3.7H_4.6O_0.8, C_3.7H_4.6O_0.8 + 4.45 O₂ = 3.7 CO₂ + 2.3 H₂O, RQ = 3.7/4.45 = 0.831,

²Tripalmitoylglycerol (C₅₁O₆H₉₈),

³Palmitate