Final answer:
The measurement of energy expenditure by analyzing respiratory gases is called indirect calorimetry, which can be assessed using methods like the Benedict-Roth spirometer or the Douglas bag method. It provides information about metabolic rates and the energy sources utilized during various activities.
Step-by-step explanation:
The method of estimating energy expenditure by measuring respiratory gases is known as indirect calorimetry. This technique estimates metabolic rates by calculating oxygen consumption and carbon dioxide production. Two primary methods used in indirect calorimetry are the Benedict-Roth spirometer method, which is ideally used when a person is at rest, and the Douglas bag method, which can measure gas exchange during varying levels of activity. Another related concept is the respiratory quotient (RQ), which is the ratio of carbon dioxide produced to oxygen consumed and provides insight into which type of fuel (carbohydrate, fat, protein) is being oxidized for energy by the body.
Energy consumption is directly linked to oxygen consumption because our body's metabolic process involves the oxidation of food. The Douglas bag method, for instance, allows precise measurement of both oxygen and carbon dioxide levels during different intensities of exercise, thus providing a clear indication of energy expenditure. With indirect calorimetry, the relationship between oxygen utilization and energy output is fundamental, resting on the principle that the consumption of 1 liter of oxygen roughly equates to the production of 20 kilojoules (kJ) of energy, regardless of the food source.