Basal metabolic rate (BMR) refers to the energy metabolic rate of the human body when it is awake and extremely quiet, not affected by muscle activity, ambient temperature, food and mental stress.That is, the amount of heat needed to maintain basic functions such as normal breathing, heart rate and cellular activity.When the person is in long-term hunger or nutrition is insufficient, can appear basic metabolization is reduced.Aging also lowers your basal metabolic rate.