The method on which the measurement is based is called indirect calorimetry and is based on the fact that oxygen (O ₂ ) is used during the oxidation of food and carbon dioxide (CO _{) is produced. 2} ), in proportion to the heat production.

Measuring Resting Metabolic Rate (RMR) is fast and simple. It includes a short, non-invasive test, during which the examinee rests on a test bed and breathes through a silicone mask. The examinee is not required to do anything but calm down and breathe normally for 12-15 minutes.

As it is important, you need to keep some conditions before the measurement. That is:

• 4 hours before measuring basal metabolism, do not consume food, water or other fluids.
• Avoid exercising for at least 8 hours.
• 24 hours without alcohol.
• Have not smoked for 4 hours before the measurement (including e-cigarette with nicotine).

The measurement of basic metabolism in the diet office is done with a Cosmed Fitmate machine.