Basal metabolic rate (BMR) is the number of calories your body needs to maintain basic physiological functions while at rest, such as breathing, circulation, and cell production. It represents the energy expenditure required to keep your body functioning in a state of rest, without any physical activity or digestion involved. BMR is influenced by several factors, including age, gender, weight, and body composition. For example, individuals with more muscle mass typically have a higher BMR because muscle tissue requires more energy to maintain than fat tissue. Understanding your BMR can help in managing weight loss or weight gain goals effectively.