The amount of calories a person burns naturally in a day depends on factors such as gender, height, current weight and age, according to SFGate. The process of naturally burning calories without added activity is called basal metabolic rate, or BMR.
Between 60 to 70 percent of the energy consumed by the human body is used for basic functions and maintenance. People who choose to rely only on their BMR to lose weight may find weight loss difficult without significantly reducing daily calorie consumption, according to SFGate. Men have a higher metabolic rate than women, and young people tend to have a higher metabolic rate than older people.