Resting metabolic rate (RMR) represents the minimum energy your body needs to keep you alive: heartbeat, breathing, maintaining body temperature. It’s the energy your body uses at rest. Knowing your RMR helps improve your overall fitness and weight management. The amount of energy you put into your body (caloric intake) is balanced against the amount of energy you expend. Knowing your RMR helps determine the level of physical activity necessary to lose body fat and replace it with muscle.