A method of estimating energy expenditure by measuring respiratory gases. Oxygen consumption and carbon dioxide release is measured (see open circuit spirometry, closed-circuit spirometry) and the Respiratory Exchange Ratio (RER) calculated to establish which type of food is being oxidized. It is assumed that each food type liberates a given amount of energy for each litre of oxygen consumed, and that the body's oxygen and carbon dioxide content remain constant. Total energy expenditure is estimated from the RER and total oxygen consumption.
Subjects: Sports and Exercise Medicine.