Metabolism, quite simply, is the conversion of food to energy. Metabolic rate is a measure of how much food, or fat, is converted to energy in a day. Resting metabolic rate (RMR) is the measurement of how much food, or energy, is required to maintain basic body functions such as heartbeat, breathing, and maintenance of body heat while you are in a state of rest. That energy is expressed in calories per day.

This 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. The results of a Resting Metabolic Rate test can tell your doctor if you have an increased or decreased metabolism. This information can be used to determine the amount of calories you need to eat each day to maintain or lose weight.