Respiratory Gas Measurement

Indirect calorimetry is described as the gold-standard laboratory method for measuring metabolism through respiratory gases. Respiratory exchange ratio relates oxygen consumed to carbon dioxide produced. Carbohydrate use produces more carbon dioxide relative to oxygen use than fat use. Fuel mix can be inferred by analyzing respiratory gases. Conventional indirect calorimetry has not typically been used for daily self-tracking because it is cumbersome and requires specialized equipment and personnel.