The Resting Metabolic Rate test (RMR) determines the amount of energy (calories) your body is using at rest. During the Resting Metabolic Rate test you will be asked to relax in a chair while your oxygen uptake and carbon dioxide output are measured for 16 to 20 minutes. A measurement is made by analyzing the amount of oxygen your body uses and the amount of carbon dioxide your body produces. Almost all of the energy your body produces is created through aerobic (oxygen utilizing) metabolism. The oxygen is combined with carbohydrates and fats to make energy in your body’s tissues. This energy is used to keep your organs and tissues working properly. When carbohydrates and fats are broken down to make energy carbon dioxide is produced. The percentage of the energy created from carbohydrates and fats can be determined by measuring the carbon dioxide your body produces.