What Is RMR?

Resting Metabolic Rate (RMR) is the amount of energy expended by the body at rest to maintain essential physiological functions such as respiration, circulation, cellular repair, and thermoregulation. It represents the largest portion of daily energy expenditure—typically 60–75%—and is primarily influenced by lean body mass, as metabolically active tissues like muscle, liver, heart, and brain require more energy to function. RMR is regulated by various factors including age, sex, genetics, and hormone levels (notably thyroid hormones and catecholamines), and can be suppressed under conditions of caloric restriction or metabolic adaptation. Scientifically, RMR is commonly measured using indirect calorimetry, which calculates energy expenditure based on oxygen consumption and carbon dioxide production, providing valuable insight for personalized nutrition and training interventions.