An RMR (resting metabolic rate) test measures how many calories a person burns at rest. Essentially, it measures the calories (energy) needed for a person to maintain basic bodily functions while he or she is sitting or lying down.

The RMR test is non-invasive and painless. For accurate results, a person must relax for at least 30 minutes and fast at least four hours prior to the test. It takes approximately 15 minutes and involves wearing a mask that measures oxygen consumption and carbon dioxide production. With an accurate number of calories burned, an RMR test can be used to develop a nutritional guide and exercise plan from weight loss, maintenance, or gain.

A complement to the RMR test is the VO2 test. The VO2 test measures how efficient your heart, circulation, and lungs operate during exercise. The VO2 test typically takes from 10 to 15 minutes and is performed during exercise. The exercise begins slowly (in speed and intensity) and is gradually increased to a person’s point of fatigue. While exercising, the person wears a mask that feeds into an oxygen consumption analyzer. The analyzer measures the amount of oxygen in each inhalation and exhalation. The RMR and VO2 tests are commonly paired to create an comprehensive weight loss plan.