The amount of calories a person’s body burns to maintain basic vital functions, such as breathing, blood circulation, repairing cells, growing and maintaining a heartbeat, is known as the basal metabolic rate, or metabolism. Basal metabolic rate accounts for 60% to 75% of the calories a person burns each day. The remainder are burned from physical activity, from walking the dog or playing the piano. A person’s basal metabolic rate is influenced by a number of factors, such as age, body composition, and gender.